2014 convention & 11th international conference on...

International Association for Gondwana Research Conference Series 20

2014 Convention &

11th International Conference on

Gondwana to Asia

Beijing, China, September 20-21, 2014

Editors

M.Santosh, A.P.Pradeepkumar and E.Shaji

Abstract volume

International Association for Gondwana Research Conference Series 20

2014 Convention

&

11th International Conference on Gondwana to Asia

Abstract Volume

Editors

M.Santosh1, A.P.Pradeepkumar2 and E.Shaji2 1School of Earth Sciences and Resources, China University of Geosciences Beijing,

Beijing 100083, P.R. China. E-mail: [email protected]

2 Dept of Geology, Univ of Kerala, Trivandrum 695 581, India

Published by the International Association for Gondwana Research

IAGR Conference Series No. 20, pp.1–188+ix

2014

© International Association for Gondwana Research

China University of Geosciences Beijing,

29 Xueyuan Road,

Beijing 100083, China.

E-mail: [email protected]

Production by:

IAGR India Headquarters

Department of Geology

University of Kerala, Trivandrum 695 581, India

mailto:[email protected]

Contents

Mineralization mechanism of the Huangshan gold deposit hosted by a giant shear zone in Zhejiang Province, China: Implications from EPR and EPMA

S.Vijay Anand, Li Zilong, Hu Yizhou, Fu Xuheng, Zhu Yuhuo ………………………………………………1

Fluid Inclusion, Rb-Sr, Sm-Nd isotopic Study of tungsten mineralized Degana and Balda granite, Rajasthan, India

S.Vijay Anand, M.S.Pandian, R.Sivasubramanium, Zilong Li……………………………….………………3

Paleostress reconstruction from calcite twin and thrust data in the Khao Khwang Fold-Thrust Belt: implications for the Triassic evolution of the Indosinian Orogeny in Central Thailand

Francesco Arboit, Khalid Amrouch, Alan S. Collins, Rosalind King, Christopher K. Morley................5

Unravelling the Mozambique Ocean conundrum using a triumvirate of zircon isotopic proxies on the Ambatolampy Group, Central Madagascar

Donnelley Archibald, Alan S. Collins, John Foden, Justin Payne and Théodore Razakamanana……...6

Isotope evolution of magma sources of the Yoko-Dovyren intrusion, northern Transbaikalia, Russia A.A Ariskin, L.V. Danyushevsky, E.G Konnikov, E.V. Kislov, A. Kostitsyn Yu, G. S. Nikolaev …….....….8

The age and origin of the Western Ethiopian Shield Morgan L. Blades, Alan S. Collins, John Foden, Justin Payne, Xiaochen Xu, and Tadesse Alemu, Girma

Woldetinsae…………………………………………………………….......................................................10

Proterozoic vs Phanerozoic geodynamics and speculations on the supercontinent cycle Michael Brown……………………………………………………………………………………………………11

Middle Paleozoic sedimentary province: A new Tectono-Stratigraphic entity within Sino-Korean Craton

Ki-Hong Chang…………………………………………………………………………………………….……..14

Proterozoic orogenic belts of India: a critical window to Gondwana T.R.K.Chetty…………………………………………………………………………………………..................16

Detrital zircon and muscovite provenance Constraints on the Evolution of the Cuddapah Basin, India

Alan S. Collins, Sarbani Patranabis-Deb, Emma Alexander, Cari Bertram, Georgina Falster, Ryan Gore, Julie Mackintosh, Pratap C. Dhang, Fred Jourdan, Justin Payne, Guillaume Backé, Galen P.Halverson, Dilip Saha....….........................................................................................................................18

The early Paleozoic tectonic transformation of the north margin of Tarim block, NW China: Constraints from detrital zircon geochronology and provenance system

Dong Shunli, Li Zhong……………………………………………………………………………………..……20 Multi-stage scenario of tectonic development of the Early Paleozoic Olkhon terrane (northern part of the Central-Asian Orogenic belt)

T.V. Donskaya, D.P. Gladkochub, V.S. Fedorovsky, A.M. Mazukabzov……………………………………22

Holocene paleoclimate reconstruction based on oxygen isotope composition of plant cellulose Hafida El Bilali……………………………………………………………………………...….........................24

iv

Large Igneous Provinces and resource exploration: metals, oil/gas and water Richard E. Ernst and Simon M Jowitt....................................................................................................25

Reflection of central Asia block structure in modern geophysical fields

Yuriy Gatinsky, Tatiana Prokhorova…………………..............................................................................27 Late Mesozoic to early Paleogene uplift and exhumation processes of the Beishan, southern CAOB: preliminary apatite fission track results

Gillespie, Jack, Glorie, Stijn, Zhang, Zhiyong, Xiao, Wenjiao., Alan S. Collins ………………………31

Tectonics of the Transbaikalian segment of the Central Asian Orogenic Belt

D.P. Gladkochub, T.V. Donskaya, A.M. Mazukabzov…………………….................................................33 Meso-Cenozoic exhumation history of Central Asia recorded by fission track and U-Th/He thermochronology: examples from the Kyrgyz Tian Shan, Russian Altai-Sayan and Chinese Beishan

Glorie Stijn, De Grave Johan, Buslov Mikhael, Gillespie Jack, Zhang Zhiyong, Xiao Wenjiao……….35 The Jiaodong gold deposits, eastern China: A global anomaly of Phanerozoic gold in Precambrian rocks

Richard J.Goldfarb, M. Santosh.............................................................................................................37

Importance of Craton Margins and Other Lithosphere Boundaries for Gold and Other Metal Exploration David Ian Groves……………………………….…………………………………………………………..……39

Late Mesozoic intracontinental orogeny in Qinling orogen, central China

Anlin Guo, Guowei Zhang, Shunyou Cheng, Anping Yao......................................................................41 Fluid inclusion constraints on gold deposition in the Taishang Deposit, Jiaodong Peninsula, China

Linnan Guo, Liqiang Yang and Zhongliang Wang……………………………………………...……………43

Geodynamic setting of Mesozoic gold metallogeny in the western Shandong Province Pu Guo, Sheng-Rong Li, M. Santosh..........................................................................................................46

Diachronous collisions across a craton-mobile belt interface in the eastern Indian shield Saibal Gupta………………………………………………………………………………………………………48

Mechanisms of gold metallogeny in the North China Craton: Insights from geophysical data Chuansong He, M. Santosh…………………………………………………………………………..…………49

Basement signature of Junggar Basin: New constraints from borehole cores and deep seismic reflection Dengfa He, Di Li, Delong Ma, Jieyun Tang, Zejun Yi, Yanhui Yang, Yichi Lian………………………….51

Petrology and fluid inclusions of garnet-pyroxenite from Vadugappatti in the Palghat-Cauvery Suture Zone, Southern India

Minako Iinuma, Toshiaki Tsunogae, M. Santosh, T.R.K. Chetty……………………....……………………52

Sr-Nd-Hf isotopic characterization of granitoids in accretionary orogens of Asia and implications for crustal development

Bor-ming Jahn, Ying Tong, Tao Wang, Kazuaki Okamoto, Galina Valui and Masako Usuki…………………………………………………………………………………………………………………….55

Youngest marine fossil evidence in Tibet for disappearance of the Tethyan Ocean

Tian Jiang, Xiaoqiao Wan and Jonathan C. Aitchison ……….………………..…………………….……58

v

Revisiting ultrahigh temperature crustal metamorphism at regional scale – causes, tectonic setting, phase

equilibria and trace element thermometry constraints Dave E. Kelsey and Martin Hand……………………………………………………………….……….…….59

Tectonic implication of the Paleozoic sequences, South Korea from detrital and overgrowth zircon U‐Pb geochronology

Sung Won Kim, Sanghoon Kwon, M. Santosh, In-Chang Ryu………………………………………...……61

Allanite compositions of alkaline magmatic suite from the southern periphery of the Dharwar Craton, southern India: implications for magma mixing processes

Airi Kobayashi, Toshiaki Tsunogae, M. Santosh………………………………………..……………………63

Permian age of HTLP metamorphism in the Garm block, Tajikistan D. Konopelko, R. Klemd, Y. Mamadjanov, D. Fidaev, S. Sergeev……...……………………………..……65

Palaeoproterozoic ancestry of Pan-African granitoid rocks in southernmost India: Implications for Gondwana

reconstructions A. Kröner, M. Santosh, E. Hegner, E. Shaji, H. Geng, J. Wong, H. Xie, Y. Wan, C.K. Shang, D. Liu, M.

Sun, V. Nanda-Kumar…………………………………………………………………………………….……………67

Neoproterozoic and middle Phanerozoic evidence of convergent orogenesis from the Imjingang-Hongseong areas, Western Gyeonggi massif, South Korea

Sanghoon Kwon, Sung Won Kim, M. Santosh…………………………………………………….………….68

A massif-type (~1.86 Ga) anorthosite complex in the Yeongnam Massif, Korea: Late-orogenic emplacement associated with the mantle delamination in the North China Craton

Yuyoung Lee, Moonsup Cho, Wonseok Cheong, Keewook Yi.................................................................70

Late ontogeny of the trilobite Tsinania shanxiensis (Zhang et Wang, 1985) from the Cambrian (Furongian) of Anhui, China and its systematic implications

Qian-Ping Lei, Qing Liu..............................................................................................................................71

Late Paleozoic tectono-depositional evolution of Junggar Basin Di Li, Dengfa He, Delong Ma, Jieyun Tang, Zejun Yi, Yanhui Yang, Yichi Lian………………………….73

Metallogenic response to the destruction of the North China Craton

Sheng-Rong Li, M. Santosh, Jun-Feng Shen, Guo-Chen Dong, Hong Xu, Ye Cao, Wen-Yan Sun, Qing Li, Ju-Quan Zhang, Lin Li, Lin-Jie Zhang, Xiao Wang, Qiongyan Yang……………………………………….75

Simian tectono–depositional evolution of Sichuan Basin and adjacent areas

Yingqiang Li, Dengfa He, Qinghua Mei, Jiao Li, Li Zhang...................................................................78

Spatial-temporal distribution and magma evolution of the Early Permian Tarim Large Igneous Province of NW China

Zilong Li, Yinqi Li, Shufeng Yanga, Yu Xing, Hanlin Chen, Siyuan Zou, Haowei Sun…………...………80

Profiling mantle carbonate metasomatism using Os-Mg isotopes of Tibetan ultrapotassic magmatism Dong Liu, Zhidan Zhao, Shan Ke, Elisabeth Widom, Di-Cheng Zhu, Yaoling Niu, Sheng-Ao Liu, Qing

Wang, Xuanxue Mo…………………………………………………………………………………………………….81

vi

The biostratigraphic succession of acanthomorphs of the Ediacaran Doushantuo Formation in the Yangtze

Gorges area, South China and its international correlation Pengju Liu………………………………………………………………………………………...………………82

Crustal carbonatite dykes within Tibetan plateau: Implications to global climate change

Yan Liu……………………………………………………………………………………………………………..84

The tantalum pegmatite deposits of Belogorskoye and Yubileinoye, Kazakhstan Mataibayeva I, Seltmann R, Shatov V……………………………….........................................................88

Lonely wanderers and Gondwana

Joseph G. Meert…………………………………………………………………………………….…………….90 Structural geometric and kinematic features and deformation mechanism of west segment of South Daba Shan

Qinghua Mei, Dengfa He, Longbo Chen, ZhuWen, Li Zhang, Yingqiang Li…………………...…………92

The Alpine Triassic development in the Southern Carpathians (Romania) Mihaela C. Melinte-Dobrinescu and Relu-Dumitru Roban………………………………………...………94

Sulfide associations in diamond-grade dolomitic marble from the Kokchetav massif (Northern Kazakhstan): Evidence for the sulfide melt presence at the UHP-conditions

Anastasia O. Mikhno, Xiao-Ying Gao, Andrey V. Korsakov...................................................................96

Late Paleozoic intra-plate volcanism of the Tienshan-Junggar Region Alexander Mikolaichuk, Inna Safonova.................................................................................................99

The Vasilkovskoye stockwork gold deposit (North Kazakhstan)

A. Miroshnikova, M. Rafailovich, D. Titov, R. Seltmann......................................................................102

Origins of the Supercontinent Cycle R. Damian Nance and J. Brendan Murphy...............................................................................................104

Devonian-Carboniferous microfossils from the southern Char Belt, East Kazakhstan

O.T. Obut and N.G. Izokh………………………………………………………………………………………105 Volcanic-related epithermal deposits in Kamchatka volcanic arc (North-East of Pacific region)

Victor Okrugin and Elena Andreeva…………………………………………………………………….……107 Glimpses on the Late Palaeozoic floral diversity of Tethyan region, Kashmir, India

Sundeep K. Pandita and Deepa Agnihotri...........................................................................................110 The chaotic nature of mantle plume periodicity

Andreas Prokoph……………………………………………………………………………………..…………112

Evolution of the continental crust; insights from the zircon record

Nick M W Roberts and Christopher J Spencer.........................................................................................113 Evaluation of juvenile versus recycled crust in the Central Asian Orogenic Belt: importance of OPS, HP belts and fossil arcs

I. Safonova...........................................................................................................................................115

vii

Partial melting process of mafic granulites from the Neoproterozoic - Cambrian Lützow-Holm Complex, East Antarctica: Evidence from crystallized melt inclusions

Yohsuke Saitoh, Toshiaki Tsunogae…………………………………………………………………….……..117 Hadean – Eoarchean crustal record from southern India

M. Santosh………………………………………………………………………………………………….……120 Provenance of the Nambucca Block (eastern Australia) and implications for the early Permian eastern Gondwanan margins

Uri Shaanan, Gideon Rosenbaum and Richard Wormald.......................................................................122

The Caucasian-Arabian segment of the Alpine-Himalayan collisional belt: geology, volcanism and neotectonics

Evgenii Sharkov, Vladimir Lebedev, Inna Safonova…………………………..…….……..…….….……..123

Gabbro-monzodiorite associations of Central Asian Orogenic Belt: Age, petrogenesis, tectonic setting Roman Shelepaev, Vera Egorova, Andrey Izokh, Andrey Vishnevsky………………………..…..………125

Late Quaternary geyserites of the Ol’khon region (northern part of the Central Asian Orogenic Belt): geological setting, age and composition

T.M Skovitina, E.V Sklayrov, O.A Sklyarova, A.B Kotov, E.V Tolmacheva, S. D Velikoslavinsky…….128

Petrology and phase equilibrium modeling of garnet-bearing mafic granulites from the Highland complex, Sri Lanka: implications for regional correlation of Gondwana fragments

Yusuke Takamura, Toshiaki Tsunogae, M. Santosh, Sanjeewa Malaviarachchi…………...……………130

Zircon U-Pb geochronology of the Songshugou ophiolite: new constraints and implications for Paleozoic tectonic evolution of the Qinling orogenic belt

Li Tang, M. Santosh, Yunpeng Dong………………………………………………………………………….132

Geochronology and geochemistry of the Damiao gabbro–anorthosite suite in the North China Craton: petrogenetic and geodynamic implications

Xueming Teng, M. Santosh………………………………………………………………….…………………134 Permo-Triassic palaeofloristics of Allan Hills, central Transantarctic Mountains, SVL, Antarctica: Palaeoecology and phytogeography

Rajni Tewari and Sankar Chatterjee.........................................................................................................136 Cu-Ni-PGE deposits of East Siberia hosted by Neoproterozoic mafic-ultramafic complexes

N.D Tolstykh, G.V Polyakov, A.E Izokh, Podlipsky M.Yu, A.S Mekhonoshin, D.A Orsoev, T.B Kolotilina............................................................................................................................................................138 Petrology and phase equilibria of charnockites: implications for Precambrian crustal evolution

Toshiaki Tsunogae and M. Santosh...........................................................................................................141 Recognition and tectonic implications of an extensive Neoproterozoic volcano-sedimentary rift basin along the southwestern margin of the Tarim Craton, northwestern China

Chao Wang, Liang Liu, Yong-He Wang, Shi-Ping He, Rong-She Li, Alan S. Collins, Meng Li, Wen-Qiang Yang, Yu-Ting Cao, Chao Shi, Hui-Yang Yu……………………………………………………………….143

viii

Zircon U-Pb geochronology, geochemical and Hf isotopes of the Zhibenshan granitoid in Baoshan Block: a magmatic response to the Proto-Tethys evolution along the northern margin of Gondwana

Changming Wang, Jun Deng, T. Campbell Mccuaig, Qingfei Wang……………………………………..146

Petrology, geochemistry and petrogenesis of Ganzhou granites in Jiangxi Province Lili Wang, Zhidan Zhao, Xuanxue Mo……………………………………………………………………….148

Metallogenic fingerprints of North China and Yangtze Craton of China: A comparison with Gondwana cratons

Yang Wang..................................................................................................................................................149

High Ba-Sr Guojialing-type granitoids in Jiaodong Peninsula, East China: Petrogenesis and geodynamic implications

Zhong-Liang Wang, Li-Qiang Yang, Hua-Feng Zhang, Yue Liu, Bing-Lin Zhang, Tao Huang, Xiao-Li Zheng, Rong-Xin Zhao..................................................... .................................................................................152

Terminal events in the Eastern segment of the Central Asian Orogenic Belt

Simon A. Wilde…………………………………………………………………………………………………..155

Significant counterclockwise rotations of the Yanshiping region, east North Qiangtang terrane, implication on the initial collision of the Lhasa and Qiangtang terranes during late Jurassic

Maodu Yan, Haidong Ren Xiaomin Fang, Chunhui Song, Dawen Zhang……………………….………158 Mesozoic gold metallogenic system of the Jiaodong gold province, eastern China

Liqiang Yang, Jun Deng, Zhongliang Wang, Liang Zhang and Linnan Guo……………………..…….159

Late Paleozoic ultrahigh-temperature metamorphism of the Altai orogenic belt of NW China: insight from pseudosection modelling and fluid inclusion

Xiaoqiang Yang and Zilong Li.............................................................................................................163

The distribution of Neoproterozoic magmatism during the breakup of the Rodinia supercontinent: Constraints from detrital zircon U-Pb ages and Hf isotopes from Qilian Orogenic Belt and North China Craton Qingyan Tang, Mingjie Zhang, Chusi Li, Hongfu Zhang, Ming Yu…...…………………….……………165

Paleoproterozoic arc magmatism in the North China Craton: Geochemical, and zircon U-Pb and Lu-Hf constraints

Qiong-Yan Yang, M. Santosh.....................................................................................................................169

Inclusions of α-quartz, albite and olivine in a mantle diamond Zuowei Yin, M. Santosh, Cui Jiang, Qinwen Zhu, Fengxiang Lu........................................................171

Japanese Student Himalayan Exercise Program

Masaru Yoshida, Kazunori Arita, Tetsuya Sakai, Bishal Nath Upreti…………………………….……..172

The Anarak Metamorphic Complex (central Iran) and its significance for the Cimmerian orogeny Stefano Zanchetta, Andrea Zanchi, Nadia Malaspina, Fabrizio Berraa, Maria Aldina

Bergomi........................................................................................................................................................174

Nature of the source rocks from the Delingha paragneiss suites, NW China and implications for Precambrian tectonics

ix

L. Zhang, Q. Y. Wang, N. S. Chen, M. Sun, M. Santosh, J. Ba……………………………………………176

S–Pb isotopic geochemical constraints on the origin of the Dayingezhuang gold deposit, Jiaodong Peninsula, China

Liang Zhang, Liqiang Yang, Zhongliang Wang, Linnan Guo, Yue Liu, Ruihong Li, Tao Huang and Ruizhong Zhang……………………………………………………………............................................................179

Behaviors of crust and upper mantle of Indian continent beneath western Tibet

Junmeng Zhao, Robert D. van der Hilst, Qian Xu, Huajian Yao, Hongbing Liu, Shunping Pei Ling Bai.......................................................................................................................................................................182

Preliminary paleomagnetic results of the 925 Ma mafic dykes from the North China Craton: implications for the Neoproterozoic paleogeography of Rodinia

Xixi Zhao, Peng Peng, Xinping Wang, and Yun Li…………………………………………………………183

Hidden magmatism revealed by post-collisional magmatism in Lhasa terrane, Tibet

Zhidan Zhao, Di-Cheng Zhu, Dong Liu, Xuanxue Mo, Don DePaolo, Yaoling Niu.............................184

A magmatic approach to date the India–Asia collision Di-Cheng Zhu, Qing Wang, Zhi-Dan Zhao, Sun-Lin Chung, Peter A. Cawood, Yaoling Niu, Sheng-Ao

Liu, Fu-Yuan Wu, Xuan-Xue Mo..................................................... .................................................................185

2014 Convention &11th International Conference on Gondwana to Asia

20-21 September 2014, Beijing, China

Abstract Volume

IAGR Conference Series No. 20, pp.1–2

Mineralization mechanism of the Huangshan gold

deposit hosted by a giant shear zone in Zhejiang Province,

China: Implications from EPR and EPMA

S.Vijay Ananda*, Li Zilonga, Hu Yizhoua, Fu Xuhenga, Zhu Yuhuob

aDepartment of Earth Sciences, Zhejiang University, Hangzhou-310027, P.R.China bZhejiang Xinsheng Gold LimitedCompany,Zhuji-311809, P.R.China

*Corresponding Author e-mail: [email protected]

The Huangshan shear zone gold deposit is related to the Proterozoic base metal inliers. The gold deposit is located in the northeastern part of the Shaoxing-Longquan Precambrian uplift in central Zhejiang and the Shaoxing-Jiangshan fault belt lying between the old Jiangnan island arc and Cathaysia block. The ore body occurs as a NE-SW trending strip along the southern edge of this fault belt. The distribution of the deposit in Huangshan area is mainly controlled by the shear deformation in the host rocks. The gold and base metal deposits in the area occur in the Proterozoic and overlying Mesozoic volcanics. The chief ore body is mainly gold occurring in pyrite, accompanied by chalcopyrite, sphalerite, galena, marcasite and pyrrhotite. The ore body has a trend of 65o and dip of 155o with the dip angle of 50-60o, and the length of ~400 m. The average grade of the ore body is 8.8 g/ton gold, locally up to 350 g/ton. The ore occurs in the lenticular vein-quartz within sheared quartz-mica-schist, phyllonite and amphibolite. Some vein minerals are strongly ductile-deformed and some others are massive with weak deformation. This suggests that there were at least two stages of vein emplacement, one formed during shear deformation, and the other in the late or post-shear period as pointed out by Pirajno (1997).

Phyllonite and mica-schist seem to be the

host rocks, showing different degrees of pyritization, silicification, chloritization, sericitization, of which the latter can be readily observed in host rocks. These alteration and deformational features mainly controlled the gold and associated ore mineralization

The present study focuses on fluid inclusion, Electron Paramagnetic Resonance (EPR) and EPMA (Electron Probe Micro Analyzer) studies on quartz and pyrite samples from the Huangshan ore deposit in Zhejiang province in order to examine the types and composition of the ore fluids, P-T-X of ore fluids and the effect of environment of ore formation, type and concentration of impurities to understand the ore genesis.

Based on the fluid inclusion study four types of primary inclusions are observed in quartz: type Ia inclusion is a bi-phase liquid-rich (L+V), the type Ib inclusion is a bi-phase vapour rich (V+L), the type II inclusion is a carbonic bi-phase (LCO2+VCO2) and the type III inclusion is aqueous - carbonic tri-phase (LH2O + LCO2 + VCO2) inclusion. Type IV

polyphase inclusions (L+V+S) are rare. Selected primary inclusions were taken to identify the composition of molecular species by using Laser Raman Spectrometer and microthermometry (Figure 1).

The EPR spectroscopic study of quartz from

2

Huangshan gold deposits obtained at room temperature (298 K), low temperature (77 K), annealing at 500 K and 800 K at one hour was used to identify the type and concentration of impurities in quartz. At room temperature the EPR spectra did not show any resonance line. At low and high temperatures, samples yielded a strong resonance line and those resonance line-associated impurities were identified with the help of ‘g’ (gyro magnetic) values (Ikeya, 1993).The resonance line in quartz samples vary due to difference in the concentration of the defect center at different temperatures. Annealing of quartz samples at 500 K and 800 K for 1 hour yielded the same resonance line with lesser intensity. These resonance lines at g ≈ 1.997 to 2.002 is attributed to germanium center [GeO4/M+] O and E1 center. In addition to the germanium center,

very strong and broad EPR spectra corresponding to Fe3+ impurity center in quartz and six hyper fine splitting due to Mn2+ center were also yielded.

We have selected some pyrite and chalcopyrite samples for EPMA analyzes to identify the invisible gold concentration in pyrite lattice. The concentration varies from 100 to 300 ppm. And there is no lattice-bound gold found in chalcopyrite minerals. The implication of this gold are potentially significant, the majority of the gold was deposited in earlier stages of pyrite as invisible gold. The solid solution process is also responsible for deposition of invisible gold in pyrite lattice. The Au3+ can substitute in Fe3+ in pyrite lattice structure and the plausible mechanism of formation of invisible gold deposits may be due to fluid-rock interaction and phase immiscibility in pyrite.

Fig. 1. Laser Raman spectra of the Huangshan shear zone deposit (13HS07). CO2 doublets (1285 cm-1

& 1385 cm-1), H2O liquid (3200 to 3600 cm-1) identified from Bi-phase (L+V) and (V+L), tri-phase (L1+L2+V) inclusions in typical gold associated ore deposits in Huangshan area, Zhejiang Province)

References

Ikeya, M. (1993): New Applications of EPR Dating, Dosimetry and Microscopy, World Scientific Publishing, Singapore.

Pirajno, F., Bagas, L., Hickman, A.H., Gold Research Team, 1997. Gold mineralization of the Chencai–Suichang Uplift and tectonic evolution of Zhejiang Province, southeast China. Ore Geol. Rev., 12, 35–55.

Weil, J.A. (1984): A review of electron spin spectroscopy and its application to the study of paramagnetic defects in crystalline quartz. Physics and Chemistry of Minerals, v. 10, 149-165.

Fluid inclusion, Rb-Sr, Sm-Nd isotopic study of tungsten

mineralized Degana and Balda granite, Rajasthan, India

S.Vijay Anand*, M.S.Pandianb, R.Sivasubramaniumb,c, Zilong Lia

aDepartment of Earth Sciences, Zhejiang University, Hangzhou-310027, .P.R.China bDepartment of Earth Sciences, Pondicherry University, Puducherry-605014,India cAtomic Minerals Directorate for Exploration and Research, Nagarabhavi, Bangalore-560072, India *Corresponding author e-mail: [email protected]

The Aravalli craton in the northwestern part of the Indian shield has witnessed several episodes of magmatism since 3600 Ma, with prominent acid magmatism during the period from 900 to 700 Ma. Some of these granites emplaced along the western fringe of South Delhi Fold Belt are associated with tungsten mineralization, including well known tungsten deposits in Degana and Balda areas.

In the Degana tungsten deposits, granite magmatism has produced three successive intrusions of porphyritic granites and a large number of aplite dykes, emplaced within phyllite. Intrusion-centered hydrothermal activity has resulted in extensive fracturing of the granitic rocks and the development of greisen veinlets, greisen-bordered lodes, and breccia fill.

Field relationships showed that there were two consecutive cycles of magmatic and hydrothermal events, which produced three types of porphyritic granites, aplitic dykes, greisen veinlets and wolframite mineralized lode/breccia fill during each cycle. The granitic rocks are greisenised adjacent to the lodes, the width of alteration zone varying from few cm to several meters, and composed of grey quartz, dark green zinnwaldite and minor topaz, fluorite and wolframite. These lodes commonly show crustification with zinnwaldite/muscovite lining

the vein walls and quartz occupying bulk of the veins along with disseminated topaz, fluorite and wolframite. The composition of wolframite is ferberite (Mn/Fe ratios ranging from 0.02 to 0.33) (Pandian, 1999).

Fluid inclusion studies were carried out on quartz from the three types of wolframite ore bodies, namely granite-hosted lode, stockwork ore in phyllite and breccia ore and mineralized granite. Four types of primary fluid inclusions are present in quartz from various ore bodies (Fig. 1).

In Type I aqueous biphase inclusions Tm-ice

varies from –18 to –0.6 oC corresponding to salinity of 21 to 1.1 wt% NaC1 equivalent, and most of these inclusions homogenized into liquid between 120 and 350 oC. Teut of Type I inclusions ranges from -26 to -22 °C in some inclusions and -59 to -42 °C in others, suggesting presence of major cations such as Na+, K+, Ca2+, Mg2+ in solution respectively. In Type II aqueous-carbonic inclusions and Type III carbonic mono-phase inclusions, Tm-CO2 ice was recorded between -63.0 and -56.5 °C with a majority of the values close to -58 °C to -60 °C. Th-CO2 (L+V→ L) in these inclusions varies between18 and 30 oC. The Tm-

Clathrate in Type II inclusions ranges from 5.0 to 18 °C.

Laser Raman microprobe analysis of the Type II and Type III inclusions showed the



Abstract Volume



4

presence of CO2, CH4 and graphite. Type IV polyphase inclusions have salinity ranging from 30 to 50 wt% NaC1 equivalent. These inclusions contain halite and sylvite as the daughter crystals which are identified from SEM-EDX analysis. The P-T condition of entrapment has been calculated from the intersection of isochores of coexisting inclusions.

Samples of granitic rocks from Degana and Balda granites were prepared for geochemical and isotopic analysis to establish the age of the mineralized granites, identifying their source and constraining their petrogenesis by Rb-Sr and Sm-Nd isotopic geochemistry respectively. Geochemically, these granites are peraluminous,

enriched in Rb, Li, F, B and depleted in Sr and Ba and strongly differentiated granites. Rb-Sr and Sm-Nd isotopic systems were used to understand tectono-thermal events for the 900-700 Ma period. This period is significant in the breakup history of the Rodinia supercontinent. The results of the Degana and Balda granite ages are comparable with Madagascar, Seychelles, Australia and South China. Rb-Sr isotopic system yielded an age of 795±11 Ma for the Balda granite and 827±8.2 Ma for the Degana granite. Sm-Nd isotopic studies suggest that Sm/Nd ratios of the Balda and Degana granites were modified by crustal derived hydrothermal fluids soon after their formation (Zachariah et al.,1996).

Fig. 1 Granite hosted lode in Rewat hill, and different types of fluid inclusions in quartz

References

Pandian, M.S. (1999): Late Proterozoic acid magmatism and associated tungsten mineralization in NW India. Gondwana Research, v.2, pp.79-87.

Zachariah J K, Mohanta M K and Rajamani V (1996): Accretionary evolution of the Ramagiri Schist Belt, Eastern Dharwar Craton; Jour. Geol. Soc. India v. 47 pp. 279–291.

CoreWall

CoreWall

a b

e

c

Graphite

d

Type Ia Type Ib

Type IV

NaCl

NaCl

Type IIa Type IIb

b

Type III

f g

Paleostress reconstruction from calcite twin and thrust

data in the Khao Khwang Fold-Thrust Belt: implications

for the Triassic evolution of the Indosinian orogeny in

central Thailand

Francesco Arboita, Khalid Amrouchb, Alan S. Collinsa, Rosalind Kinga, Christopher

K. Morleyc

aCentre for Tectonics, Resources and Exploration (TraX), Department of Earth Sciences, The University of

Adelaide, SA 5005, Australia bCentre for Tectonics, Resources and Exploration (TraX), Australian School of Petroleum, The University of

Adelaide, SA 5005, Australia cDepartment of Geological Science, Chiang Mai University, Chiang Mai, 50200, Thailand

A new approach to paleostress analysis using the multiple inverse method with calcite twin data including untwinned e-plane has been performed in the Khao Khwang Fold-Thrust Belt (KKFTB) in Central Thailand. Palaeostress states, caused by the collision of the Sibumasu and Indochina Blocks during the Triassic, have been detected from a combination of field-based data (joints, veins, pressure-solution surfaces and fault-slip data) and calcite-twin data. The

KKFTB formed by forward (north) propagating deformation in the Triassic and the cover strata of the Khao Khad Formation has been transported by numerous in-sequence thrusts. The in-sequence, thin-skinned, deformation demonstrates that strain has migrated from S-SSE to N-NNW along a zone as wide as the fold and thrust belt itself, with lateral variations probably attributed to lateral facies variations.



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IAGR Conference Series No. 20, pp.5



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Unravelling the Mozambique ocean conundrum using a

triumvirate of zircon isotopic proxies on the

Ambatolampy group, central Madagascar

Donnelley Archibalda, Alan S. Collinsa, John Fodena, Justin Paynea and Théodore

Razakamananab

aTectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, The University of

Adelaide, Adelaide, Australia bDépartement des Sciences de la Terre, Université de Toliara, Toliara, Madagascar

Madagascar occupies an important location within the East African Orogen (EAO). The EAO involves a collection of Neoproterozoic microcontinents and arc terranes lodged between older cratonic units during the final assembly of the supercontinent Gondwana. The Malagasy basement preserves a record of the style and timing of amalgamation of Neoproterozoic India with the Congo/Tanzania/Bangweulu Block during the final closure of the Mozambique Ocean.

Central Madagascar is comprised of a number of Precambrian units. The oldest blocks, the Antongil and Masora cratons, consist of Mesoarchaean ortho- and para-gneiss cores in addition to Neoarchaean granitic and metasedimentary rocks. The largest unit, the Antananarivo Block, underlies the central highlands and consists of Neoarchaean granite interlayered with voluminous Cryogenian to Cambrian granite, syenite, and gabbro, the majority having subduction zone geochemical characteristics. Overlying the Antananarivo Block are Proterozoic metasedimentary packages (Ambatolampy, Manampotsy, Vondrozo and Itremo-Ikalamavony groups). The

Ambatolampy, Vondrozo and Manampotsy groups are major siliciclastic metasedimentary successions characterised by a pelite-quartzite association. The Itremo–Ikalamavony suite consists of probable Palaeoproterozoic greenschist- to amphibolite-facies metasedimentary rocks and is intruded by Cryogenian granitoids and gabbro. Previously, the group was interpreted to be a Neoproterozoic sequence with a maximum depositional age of ~1056–650 Ma. The minimum depositional age (~560 Ma) was constrained by metamorphic zircon ages and by intrusive relationships with the Ediacaran Ambalavao Suite. New U-Pb zircon data (SHRIMP) for the Ambatolampy Group shows age populations of ~3000 Ma, ~2800–2700 Ma, ~2500 Ma, ~2200- 2100 Ma and ~1800 Ma. We do not find the rare Mesoproterozoic zircons reported (but incompletely published) by others. Hence, we tentatively suggest that the Ambatolampy Group may be older than previously thought since the youngest concordant detrital zircon age is ~1800 Ma, similar to the Itremo–Ikalamavony Suite. Metamorphic zircons and rims indicate the minimum depositional age to be ~540 Ma. Here

we present new U-Pb data with complementary del18O (SHRIMP SI), and Hf (MC-LA-ICP-MS) isotopic data for Ambatolampy Group detrital zircons, thus providing new constraints on the age, geochemistry and provenance of the metasedimentary rocks. We then compare these new data with analogous metasedimentary sequences elsewhere in the EAO and discuss the tectonic implications of these data.



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IAGR Conference Series No.20, pp.8–9

Isotope evolution of magma sources of the Yoko-

Dovyren intrusion, northern Transbaikalia, Russia

A.A.Ariskina, L.V.Danyushevskyb, E.G.Konnikovc, E.V.Kislovd*,

Yu.A Kostitsyna, G.S.Nikolaeva

aV.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Science Academy, Moscow, Russia,

[email protected] b Tasmanian University, Hobart, Australia, [email protected] cInstitute of Experimental Mineralogy, Russian Science Academy, Chernogolovka, Russia dGeological Institute, Siberian Branch, Russian Science Academy, Ulan-Ude, Russia *Corresponding author e-mail: [email protected]

The Synnyr-Dovyren volcano-plutonic complex (~728 Ma; Ariskin et al., 2013) is located within the Baikal-Muyaorogenic belt of northern Transbaikalia, at the south-eastern folded frame of the Siberian Craton. It consists of the fertile Ioko-Dovyren layered intrusion (Cu-Ni-PGE mineralisation), underlying ultramafic sills, leuco-norite and gabbro-diabase dikes, and associated volcanics. We present Sr-Nd-Pb isotopic compositions of 24 intrusive rock samples and five samples of the associated low-Ti and high-Ti basalts. The isotopic composition of the high Ti-basalts is similar to the MORB source at the time of emplacement (0.7028 87Sr/86Sr(t) 0.7048 and 4.6 Nd(t) 5.8).

Intrusive rocks and the low-Ti basalts are geochemically similar, being characterised by anomalously enriched radiogenic compositions of Sr, Pb and Nd. The maximum enrichment (87Sr/86Sr(t) = 0.713870.00010 (2), Nd(t) = −16.090.06) is found in the lower marginal rocks of the layered intrusion, which are the crystallisation products of the most primitive high-Mg magmas. Dunites, troctolites and

gabbros of the main Ioko-Dovyren intrusion are less enriched, which most likely reflects assimilation of the wall rocks at the site of emplacement and/or minor heterogeneity of the parental melts. Mixing calculations indicate that it is unlikely that the intra-complex variations are due to assimilation of carboniferous sedimentary units at the site of emplacement, as unrealistically large extents of assimilation (40-50%) would be required. More likely, these variations are due to mixing with 5-10% of the high-Ti component, indicating possible mixing of two different magma types which coexisted in this location in the late Proterozoic.

Overall, minor variations in Nd(t) among the intrusive and extrusive rocks (−14.31.1) indicate that magmas that formed the entire complex were derived from an isotopically anomalous source. The time-dependent evolution of Nd(t) indicates that the protolith of this source can be formed by melts formed by melting of the mantle at 2.8 Ga. Thus the Dovyren parental melts formed in the late Proterozoic from a sub-lithospheric mantle source which was metasomatised ~ 2 Gy earlier

by a mafic component with a low Sm/Nd value. The source then remained isolated from the convecting mantle. Additional support for this hypothesis of an old, re-activated source comes from the fact that the trend of Nd isotopic evolution over time is shared by the Dovyren rocks and the paleo-Proterozoic gabbroids of the Chiney massif, Archaean granites and enderbites

of the Baikal region. Geochemical features of the ultramafics, mafic rocks, granulites and granitoids from the southern margin of the Siberian craton suggest that the metasomatised mantle source was formed above a subduction zone which contributed to crustal accretion of the Siberian craton ~ 2.8 Ga.

Acknowledgments

This work was performed in the frame of a

Russian-Australian project supported by AMIRA International grant no. P962 (2007-2010) and RFFI grants nos. 11-05-00268, 11-05-00062. Contribution to IGCP project # 592.

References

Ariskin, A.A., Kostitsyn, Yu.A., Konnikov, E.G., Danyushevsky, L.V., Meffre, S., Nikolaev, G.S., McNeill, A., Kislov, E.V., Orsoev, D.A. 2013. Geochronology of the Dovyren intrusive complex, northwestern Baikal area, Russia, in the Neoproterozoic. Geochemistry International, 51, 859-875.

The age and origin of the western Ethiopian shield

Morgan L. Bladesa, Alan S. Collinsa, John Fodena, Justin Paynea, Xiaochen Xua, and

Tadesse Alemub, Girma Woldetinsaec


Adelaide, Adelaide, SA 5005, Australia. bMinistry of Mines & Energy, P.O.Box 26865, Addis Ababa, Ethiopia cGeological Survey of Ethiopia, Addis Ababa, Ethiopia Department of Earth Sciences, Zhejiang University,

Hangzhou-310027, .P.R.China

The Western Ethiopian Shield (WES) lies within the East African Orogen, a major Gondwana-forming collisional zone. It contains poorly dated and poorly geochemically characterised terranes that host significant ore systems. The Western Ethiopian Shield lies close to the Western cratonic margin of the East African Orogen, and forms a transition between lower crustal rocks found in the southern East African Orogen (known as the Mozambique Belt), and upper crustal rocks of the northern Arabian-Nubian Shield. The East African Orogen preserves a complex history of intra-oceanic and continental margin, magmatic and tectonothermal events. The region formed during the Neoproterozoic subduction of the Mozambique Ocean, which separated India from African continents in the Neoproterozoic, and was deformed and amalgamated during the late Neoproterozoic- Cambrian assembly of Gondwana. Despite linking these regions together, being well exposed, and accessible, it has received little modern geological investigation.

This paper focuses on constraining the age

and origin of the Neoproterozoic sediments and igneous sequences within the Western Ethiopian Shield. The U-Pb and Hf isotopic analysis of zircons is used to define the maximum depositional age and provenance of the protoliths of the meta-sedimentary units, as well as constraining the age of igneous intrusions located within the Western Ethiopian Shield.

Radiogenic isotopic analysis of volcanic and volcaniclastic successions of the WES revealed positive ƐNd values signifying relatively juvenile sources. Collectively, the data provides provenance and geochemical information as to whether the protoliths formed as Neoproterozoic volcanic arcs, created as a result of subduction and the closure of the Mozambique Ocean, during the amalgamation of Gondwana. Preliminary data supports the interpretation that the Neoproterozoic terrane was, in part, formed as the result of the closure of a Neoproterozoic ocean (Mozambique Ocean) and the formation of an arc. However, it was not an intra-oceanic arc as sediments clearly show sources that are consistent with being derived from cratonic Africa.



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Proterozoic vs Phanerozoic geodynamics and

speculations on the supercontinent cycle

Michael Brown

Laboratory for Crustal Petrology, Department of Geology, University of Maryland, MD 20742, USA

This work presented here is part of a larger project to use the geological record of magmatism and metamorphism—proxies for secular change in ambient mantle temperature and for the thermal structure of different tectonic environments, respectively—to develop hypotheses about geodynamics that may be tested using numerical modeling (Sizova et al., 2010, 2012, 2014). Secular change in ambient mantle temperature is constrained by retrieving primary melt compositions from non-arc basalts and komatiites in greenstone belts. These data show that the Mesoarchean ambient mantle temperature was higher than the contemporary mantle by 150–300ºC and that secular cooling has dominated the thermal history of Earth since the Neoarchean (Johnson et al., 2014). Apparent thermal gradients of metamorphism, as recorded by close-to-peak mineral assemblages, are retrieved from rocks equilibrated at high P, P–T or T, for which the timing is obtained from a variety of chronometers. Using these data, the geological record may be interrogated to assess secular change in the apparent thermal gradients of metamorphism for different tectonic settings since the Mesoarchean (Brown, 2014). One-sided subduction creates asymmetry in the thermal structure of convergent plate margins, with lower dT/dP in the subduction zone and higher dT/dP in the orogenic hinterland. During collisional orogenesis these distinct thermal environments are imprinted in the rock record as contrasting types of metamorphism

distinguished by different apparent thermal gradients. Proterozoic orogens present eclogite–HP granulite metamorphism, with gradients of 350–750 °C/GPa, and granulite–UHT metamorphism, with gradients of 750–1500 °C/GPa (Fig. 1a). By contrast, in addition to eclogite–HP granulite metamorphism, Phanerozoic orogens manifest UHP metamorphism with strikingly lower gradients of 150–350 °C/GPa (Fig. 1a).This is the beginning of the modern plate tectonics regime (Brown, 2006, 2007).UHP rocks first appear in the Zambezi (late Cryogenian) and Gourma (Ediacaran) belts in south and west Africa, and diamonds appear first at Kokchetav in the North Tianshan (Cambrian) belt. Once established, UHP metamorphism became the defining feature of Phanerozoic orogenesis in Eurasia. By contrast, contemporaneous (Ediacaran–Cambrian) granulite facies and UHT metamorphism characterizes central East Gondwana (eastern Africa, Madagascar, southern India and Sri Lanka), and many other Pan-African belts, but UHT metamorphism virtually disappeared from the rock record after the Cambrian. What is the change in geodynamics recorded by these data?

For contemporary conditions, geodynamic modeling of collisional orogenesis shows that slab breakoff occurs at depths >300 km; strong lower crust results in coupled collision with UHP metamorphism, whereas weak lower crust results in decoupled collision with only



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eclogite–HP granulite metamorphism (Sizova et al., 2012). Increasing the ambient mantle temperature by 80–100 °C leads to shallow slab breakoff (< to << 200 km) and unconventional modes of collision (Sizova et al., 2014), viz a truncated hot collision regime (strong lower crust) and a two-sided hot collision regime (weak lower crust). Inverting these data, as ambient mantle temperature declined to <100 °C warmer than the present day the change to deeper slab breakoff generated a colder environment and enabled stronger crust–mantle coupling that allowed subduction of continental rocks to mantle depths, and the appearance of UHP metamorphism was a consequence of secular decrease in ambient mantle temperature. By contrast, granulite facies and UHT metamorphism in central East Gondwana likely represents deep crust metamorphosed under a large, moderately thick orogenic plateau that formed as a result of Ediacaran collision and hinterland thickening, with radiogenic heating generating peak metamorphic temperatures in the Cambrian. It may be no coincidence that Gondwana could have been located over the African LLSVP at the dawn of the Phanerozoic or that the Zambezi, Gourma and North Tianshan belts had a subduction polarity broadly towards the core of East Gondwana. The Neoproterozoic to Paleozoic transition also witnessed a change in the style of continental breakup and aggregation. In a Hoffman breakup, continental lithosphere fragments, disperses and reassembles by elimination of the complementary super ocean; such was the process by which the Gondwanan elements of

Rodinia were transformed into Gondwana. By contrast, in a Wilson cycle sensu stricto, continental lithosphere simply fragments and reassembles along the same (internal) contacts, closing an internally generated ocean basin. Wilson cycles involving terrane transfer were responsible for the transformation from Pannotia to Pangea. Internally generated ocean basins were opened and closed asymmetrically by rifting of ribbon terranes from the northern margin of Gondwana and their accretion to Laurentia, Baltica and Siberia forming the Caledonides, Variscides and Altaides, as reflected in an essential continuous record of HP-UHP and E-HPG metamorphism from the Cambrian to the Triassic (Fig. 1a). The change was also registered by multiple geochemical indices, such as Hf(T) and 87Sr/86Sr, with complex temporal records characterized by short wavelength variations that reflect the overlapping opening and closure of several major oceans (Iapetus, Rheic, Paleotethys and Neotethys). This pattern is superimposed on a simpler long wavelength variation in Hf(T) and 87Sr/86Sr that is temporally related to the supercontinent cycle (Figs 1b,c,d). The balance between continental vs oceanic influence registered by these indices suggests differences in the geodynamics of supercontinent formation. There are many other features of the Cryogenian–Cambrian record that indicate a period of profound change, including environmental perturbations and variations in chemostratigraphy, as well as the ‘explosion’ in the diversity of life.

13

Fig. 1

References

Brown, M., 2006.Duality of thermal regimes is the distinctive characteristic of plate tectonics since the Neoarchean. Geology 34, 961–964.

Brown, M., 2007. Metamorphism, plate tectonics, and the supercontinent cycle. Earth Science Frontiers 14, 1–18.

Brown, M., 2014.The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics. Geoscience Frontiershttp://dx.doi.org/10.1016/j.gsf.2014.02.005

Cawood, P.A., Hawkesworth, C.J., Dhuime, B., 2013.The continental record and the generation of continental crust. GSA Bulletin 125, 14–32.

Johnson, T.E., Brown, M., Kaus, B., VanTongeren, J.A., 2014.Delamination and

recycling of Archaean crust caused by gravitational instabilities. Nature Geoscience 7, 47–52.

Keto, L.S., Jacobsen, S.B., 1988.Nd isotopic variations of Phanerozoic paleo-oceans. Earth and Planetary Science Letters 90, 395–410.

Prokoph, A., Shields, G.A., Veizer, J., 2008.Compilation and time-series analysis of a marine carbonate δ18O, δ13C, 87Sr/86Sr and δ34S database through Earth history. Earth-Science Reviews 87, 113–133.

Sizova, E., Gerya, T., Brown, M., Perchuk, L., 2010. Subduction styles in the Precambrian: Insight from numerical experiments. Lithos 116, 209–229.

Sizova E., Gerya T., Brown M., 2012. Exhumation mechanisms of melt-bearing ultrahigh pressure crustal rocks during collision of spontaneously moving plates. Journal of Metamorphic Geology 30, 927–955.

Middle Paleozoic sedimentary Province: A new tectono-

stratigraphic entity within Sino-Korean Craton

Ki-Hong Chang

Department of Geology, Kyungpook National University, Daegu 702-701, Korea

The Middle Paleozoic Sedimentary Province (MPPr), an area within the Korean Peninsula plus the Shandong-Liaoning area, China, is a marginal part of the Sino-Korean Plate lying adjacent to the Yangtze Plate. Here in MPPr, the expected 'Middle Paleozoic' (Upper Ordovician-Lower Carboniferous) hiatus characteristic of the Sino-Korean Plate is ambiguous because of the sporadic development of the local sedimentary sequences within the Middle Paleozoic time. The outline of MPPr is drawn only for convenience, and is not a structural geological boundary. Since the Yangtze Plate supplied its clastic material to the MPPr, the Yangtze and the Sino-Korean Plates which were in mutual contact could form aulacogens over the plate margins. Thus a Middle Paleozoic soft collision of the Sino-Korean and the Yangtze plates is suggested. The possible aulacogens of the Yangtze Plate margin may passively have been subducted under the Sulu (Shandong) suture zone. Since the Yellow Sea Transform Fault (YSTF) served as the plate boundary near Korea, a mild compressional state

between the two plates may have yielded an extensional upper crust where aulacognes formed. The Middle Paleozoic sedimentation in MPPr were either continued upon the earlier Paleozoic sedimentary sequences or took place anew on the Precambrian rocks. But the total time span of the Middle Paleozoic sedimentation in various sedimentary basins of MPPr corresponds to the Middle Paleozoic Hiatus. Therefore the total composite sedimentary sequences form an unconformity-bounded stratigraphic unit that may be called the Sino-Korean Middle Paleozoic Hiatal Synthem. The rift-fills of MPPr, rarely volcanic and containing Yangtze-akin shallow marine fossils, are characterized by the presence of clastic zircon grains with radiometric ages characteristic of the Yangtze Plate. Recently discovered Hercynian metamorphosed Middle Paleozoic strata in the western Metamorphosed Okcheon Zone implies that the area partly overlaps with MPPr. It suggests further discoveries of the Middle Paleozoic strata in the western metamorphosed Okcheon Zone.



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Fig. 1. A tectonic map showing 'the Middle Paleozoic Sedimentary Province' (MPPr) astride the Korean Peninsula and China (Shandong Peninsula and the Liaohe-Liaoning area). The Sulu subduction-collision zone does not extend toward the Korean Peninsula due to the Paleozoic Yellow Sea Transform Fault (YSTF) now found as submarine fault zone (WMF) shown by the thick blue line. The Late Ordovician-Early Carboniferous 'Great Hiatus' of the Sino-Korean Plate was atypically developed over the 'the Middle Paleozoic Sedimentary Province' (MPPr), where aulacogens (shown in red) were developed. A, Devonian(-Carboniferous) strata; B, Late Ordovician-Silurian strata; C, Devonian(-Carboniferous) Imjin Group; D, Devonian(-Carboniferous) Taean Formation; E, Silurian-Devonian strata in the metamorphosed Okcheon Zone; and the 'Middle Paleozoic strata' in the Liaohe area of the southern NE China.

Proterozoic orogenic belts of India: A critical window to

Gondwana

T.R.K.Chetty

CSIR-National Geophysical Research Institute, Hyderabad-500007, India

Corresponding author e-mail: [email protected]

The Precambrian orogenic belts of India preserve important rock records and structural and tectonic history relating to the three major Proterozoic supercontinents – Columbia, Rodinia and

Gondwana. The Eastern Ghats Mobile Belt along the east coast and the Southern Granulite terrane at the southern tip of India represents a contiguous Proterozoic orogenic belt of southern India (POSI). The POSI extends over a length of more than 1500 km wrapping around the Archaean Dharwar and Bastar cratons (Fig.1) and defines a crucial segment of Transgondwana orogenic belts juxtaposing different continental fragments of the Gondwana supercontinent and thus making it a critical window to Gondwana supercontinent.

The POSI constitutes a network of major shear zones separating the collage of juxtaposed crustal blocks of complexly deformed high grade metamorphic and magmatic assemblages through multiple tectonothermal events spanning from the Archaean to Neoproterozoic. Recent investigations reveal that the POSI was subjected to convergent tectonics through prolonged subduction-accretion-collision processes reflecting the development of accretionary orogens and continental growth. It is aimed here to present the broad structural architecture, shear zone network, the presence of suture zones and the emplacement of ophiolite suites, the involvement of transpressional strain reflected by the geometry of crustal-scale ‘flower structures’, and multiple ocean

development and subduction events of the POSI, which witnessed oblique convergence between the continents of the Indian Dharwar and the Azania.

The following salient features of POSI can be identified: (i) The occurrence of high grade granulite facies rock assemblages with continuing structural fabrics and shear zones and similar structural styles of fold-thrust tectonics, (ii) Constitution of different crustal blocks of distinct geologic history separated by network of mid-crustal shear zones and associated episodic reactivation tectonics, (iii) Presence of high pressure granulites and ultra-high-temperature metamorphic mineral assemblages of different ages, (iv) Emplacement of Neoproterozoic anorthosites, alkaline rocks and granitoids, (v) The common occurrence of Precambrian ophiolitic complexes with ages ranging from 3.12, 2.5 to 0.8 Ga, and (vi) A wide spectrum of ages from magmatic and metamorphic rocks ranging from Neoarchean (2.5 Ga) to Neoproterozoic (0.5 Ga). The field based multi-scale structural analysis demonstrates the evolution of a network of crustal-scale shear zones and associated transpressional strain in the form of ‘flower structures’. The transpressional deformation with major strain partitioning is well reflected both in the south and in the northern parts of POSI where they are associated with Moho-upwarp and crustal uplift. However, different parts of the orogen have followed distinct evolutionary patterns during the Proterozoic, but share a common deformational



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history during the Neoproterozoic. Examination of the suture zones and their

continuity into other fragments of Gondwana supercontinent reveal their pervasive nature, perhaps representing the sites of closure of various strands of the Mozambique ocean through different periods reflecting the accretionary growth of POSI encompassing the East African orogeny and the Kuunga orogenic cycles possibly associated with the final assembly of the Gondwana supercontinent. Oblique collision and long lived transpressional tectonic regimes during Gondwana amalgamation seem to be responsible for the

present disposition, geometry, reactivation tectonics of POSI. The amalgamation of the POSI with the proto-Indian continent seems to be complex and has occurred at different places during different times. The orogenic evolution of POSI involved subduction–accretion–collision tectonics during at least two major phases: Neoarchaean and Neoproterozoic. All the geological characteristics described above are akin to Phanerozoic-style plate tectonic models, and the complexities and connections identified in the POSI can be considered as typical ancient analogues of modern orogens.

Fig. 1

Detrital zircon and muscovite provenance constraints on

the evolution of the Cuddapah Basin, India

Alan S. Collins a*, Sarbani Patranabis-Debb, Emma Alexandera, Cari Bertrama,

Georgina Falstera, Ryan Gorea, Julie Mackintosha, Pratap C. Dhangb, Fred Jourdanc,

Justin Paynea, Guillaume Backéa, Galen P. Halversond, Dilip Sahab


Adelaide, Adelaide, SA 5005, Australia bGeological Studies Unit, Indian Statistical Institute, Kolkata 700108, India cWestern Australian Argon Isotope Facility, Department of Applied Geology and John de Laeter Centre, Curtin

University, GPO Box U1987, Perth,WA 6845, Australia dDepartment of Earth and Planetary Sciences, McGill University, 3450 University Street, Montréal, QC, Canada,

H3A 2A7 *Corresponding author e-mail: [email protected]

The Cuddapah Basin is one of the largest Indian cratonic basins, covering 46,000 km2, and <10 km deep. Very little has been known about the ages of the sedimentary rocks within the basin, the provenance of the sediments and, particularly, the change of provenance through time. Because of this, basin evolution models lack the essential constraints and the significance of this basin for the tectonic evolution of Proterozoic India is therefore unknown.

The Gulcheru Fm (conglomerates and arenites) is the basal formation of the Cuddapah Supergroup and overlies Neoarchaean granitoids of the East Dharwar craton. Detrital zircons yield concordant ages at ~3.4 Ga, ~2.5 Ga and ~2.0 Ga. The Vempalle Fm (shales with desiccation cracks and halite pseudomorphs passing up into stromatolitic carbonates) gradationally overlies the Gulcheru Fm. Detrital zircons yield a unimodal age population at ~2.5 Ga. The Pulivendla Fm overlies the Vempalle Fm and

yields detrital zircons with U-Pb ages of ~2.6 Ga and ~1.9 Ga. This is overlain by the argillaceous Tadpatri Fm. The nature of the boundary with the overlying Gandikota Fm is controversial and has been described as both conformable and unconformable. The Gandikota Fm yields distinct detrital zircons with ages of ~2.6 Ga, 1.8-1.6 Ga and ~1.2 Ga. The Nallamalai Gp is tectonically isolated to the east from the rest of the Cuddapah sequence by a major N-S thrust. Detrital zircons yield ages from ~3-1.6 Ga with maxima at ~2.7 Ga, ~2.5 Ga ~1.8 Ga. The maximum depositional age is 1669±31 Ma. The Srisailam Fm yields detrital zircons with ages of ~2.6-2.5 Ga at the base of the succession, but arenites at the top of the formation yield younger zircons dated at ~2.3 Ga and 1.8 Ga. Detrital muscovites from this horizon yielded 40Ar-39Ar total fusion ages of ~1770 Ma. The Kurnool Gp unconformably overlies the Cuddapah Supergroup. In this group, the basal



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Banaganapalle Fm yields detrital zircons with U-Pb ages of 3.4 Ga, 3.0 Ga and 2.6 Ga. A stratigraphically higher quartz arenite—the Paniam Fm—yields ~2.6 Ga zircons, with the youngest concordant zircon dated at ~2.0 Ga.

Gulcheru and Vempalle Fm zircons older than ~2.6 Ga yield Palaeoarchaean TDM(Hf) ages, whereas those of ~2.5 Ga age from these formations, and from the Gandikota Fm range from mildly negative (<-5) to close to depleted mantle values (with Neoarchaean TDM(Hf) ages). Mesoproterozoic zircons from the Gandikota Fm yield positive Ε(t)Hf values. Hafnium isotopes from the Kurnool Gp show a similar pattern to those seen in the Cuddapah Supergroup samples. This suggests that they are either sourced from the same sources, or recycled from the underlying formations. Nallamalai Gp zircons yield TDM(Hf) ages from ~2.4-3.4 Ga, which is

similar to those from the Srisailam Fm, where ~2.5 Ga zircons yield much more evolved Ε(t)Hf values (>-15) than those from the Cuddapah Supergroup and Kurnool Gp (lowest ~2.5 Ga grains Ε(t)Hf values of -5).

We interpret the data to reflect an evolving rift-passive margin succession (Gulcheru, Vempalle, Pulivendla, Tadpatri Fms), sourced from the Dharwar craton, that is buried by westward prograding deposits of the late Palaeoproterozoic Krishna Orogen (Nallamalai Gp and Srisailam Fm). We suggest that the Gandikota Fm represents a lateral equivalent of the Kurnool Gp. The Kurnool Gp appears to be largely derived by reworking Cuddapah Supergroup rocks, possibly due to tectonic movements related to the distal Eastern Ghats Orogen.

The early Paleozoic tectonic transformation of the north

margin of Tarim block, NW China: Constraints from

detrital zircon geochronology and provenance system

Dong Shunli, Li Zhong

Institute of Geology and Geophysics, Chinese Academy of Sciences, 100029-Beijing, China *Corresponding author e-mail: [email protected]

As two elementary units on the earth surface, basin and orogenic belts show close affinity on spatial distribution, material transportation and surface configuration. Basin evolution is often influenced by tectonic activity that takes place in the periphery orogenic belts, on the other hand, basin depositions, especially the clastic sediments adjacent to the orogenic belts, record the orogenic tectonic evolution information to a greater extent. Hence, provenance analysis of terrigenous clastic rocks of inner basins has been a common means of studying paleogeographic reconstruction, basin-range coupling and orogenic evolution processes. Central Asian Orogenic Belt (CAOB), as the typical accretionary-type orogenic belt on the earth, has always been a natural geological laboratory from where plenty of classic tectonic models have been generated. Even so, various hot disputes still remain on some key issues, such as the oceanic opening or closure time and oceanic subduction polarity, and so forth. Tarim Block was located adjacent to CAOB to its south during the Paleozoic, thus the northern margin of Tarim Block was the transitional area between Tarim and the South Tianshan tectonic belts, the southernmost unit of CAOB. Consequently, the tectono-sedimentary nature of the Paleozoic northern Tarim continental margin is vital for us to understand the basin-range coupling process and geodynamic mechanism between CAOB

and the Tarim Block. Massive studies have been conducted on whether the northern Tarim margin was passive or active during the Paleozoic, but the conclusions from different researchers remain hugely controversial. In recent years, a large number of case studies have been carried out on matching tectono-sedimentary units between depositional areas and denuded areas and uncovering the evolutionary history of relevant terranes by using detrital zircon U-Pb geochronology and Hf isotopic compositions. With the aim to decipher the nature of the Paleozoic northern Tarim margin and gain the key information of basin-range coupling process, we conducted studies on Ordovician-Silurian detrital zircon LA-ICP-MS U-Pb dating and LA-ICP-MS-MC Hf isotopic compositions of several sandstone samples from the north margin areas of Tarim block, i.e., Quruqtagh and Tabei.

In Quruqtagh, two Upper Ordovician sandstone samples which were studied, have extremely similar U-Pb age patterns and Hf isotopic compositions, reflecting multiphase tectono-thermal events with age groups of 527–694 Ma, 713–870 Ma (peaking at 760 Ma), 904–1090 Ma, 1787–2094 Ma (peaking at 1975 Ma) and 2419–2517 Ma, which are highly consistent with those of the Tarim basement. Besides, no Early Paleozoic ages signifying subduction or collision events of the periphery tectonic-active



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belts were detected in the two samples, indicating that the Middle-Upper Ordovician detrital sediments in South Quruqtagh and northern Mangar depression were mainly derived from intracontinental uplifts, i.e., the North Quruqtagh uplift or the Tabei paleo-uplift. In terms of Hf isotopic compositions, 98 percent of 713–870 Ma detrital zircons are characterized by negative εHf (t) values ranging from −38.07 to −0.61, which can be matched well with those of Neoproterozoic granites from the Quruqtagh area. Combining the regional sedimentary features, U-Pb ages and Hf isotopic compositions, we can conclude that the northeastern Tarim margin did not experience evident tectonic activities and acted as a passive continental margin during Late Ordovician. However, the Upper Silurian sandstone samples from Quruqtagh area yield entirely different U-Pb dates and Hf isotopic composition features from the Upper Ordovician ones. Specially, a few ages of 420–430 Ma, close to the depositional time, are detected from the Upper Silurian detrital zircons, and CL images show that 420–430 Ma zircons yield euhedral crystal and magmatic oscillation zone, indicating that the provenance are proximal magmatic rocks. Coincidently, the magmatic rocks with formation ages of approximately 420 Ma have been gradually discovered in Korla area during recent years. Based on these observations, we

consider that the 420–430 Ma zircons are derived from the northeastern Tarim magmatic belts generated by the southward subduction of the South Tianshan Ocean. In other words, the southward subduction of the South Tianshan Ocean during late Silurian lead to the northeast Tarim margin to turn into an active continental margin. The sandstone-derived detrital zircon U-Pb dating and Hf isotopic compositions from Tabei area have similarities to those of Quruqtagh area, especially the Upper Silurian samples which have younger ages of 420–430 Ma, indicating that the continental margin in Tabei area experienced a tectonic evolution process similar to Quruqtagh area.

Conclusively, the clastic rocks in northeastern Tarim margin did not reveal any evidence of juvenile magmatic-arc material, indicating that the South Tianshan area was a calm phase of a retroarc generated by the southward subduction of the Terskey Ocean in Late Ordovician. With the southward subduction proceeding, the South Tianshan Ocean formed due to the retroarc extension in early Silurian which could be proved by several ophiolite age data in South Tianshan. In the late Silurian, the South Tianshan Ocean subducted southward to Tarim Block, causing the northeastern Tarim margin to change into an active continental margin, which is proved by the emergence of evident juvenile materials.

Multi-stage scenario of tectonic development of the Early

Paleozoic Olkhon terrane (northern part of the Central-

Asian Orogenic belt)

T.V. Donskayaa, D.P. Gladkochuba, V.S. Fedorovskyb, A.M. Mazukabzova

aInstitute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences,

128 Lermontov Str., Irkutsk, 664033, Russia bGeological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia

The Olkhon metamorphic terrane is located in the northern part of the Central Asian Fold Belt. It belongs to the Baikal collisional belt which could be traced up to 1500 km along the southern margin of the Siberian craton. This terrane as well as other metamorphic terranes of the Baikal belt was formed in the Early Paleozoic by the accretion and collision of numerous fragments of Neoproterozoic–Early Paleozoic island arcs and back-arc basins as well as fragments of Precambrian microcontinents to each other and their subsequent attachment to the Siberian craton.

The Olkhon terrane comprises several regional units (megazones, zones), which differ in the compositions, internal structure, geodynamic settings, and other features. The metamorphic and igneous activities within the Olkhon terrane are limited to 510–460 Ma.

According to the traditional point of view on the genesis of the Olkhon terrane it was produced by a one-stage but rather long (40–50 Ma) collision of a number of small-scale building blocks to the southern margin of the Siberian craton (Fedorovsky et al., 2005; Gladkochub et al., 2008). However, detailed investigations of different kinds of rocks which form main megazones of the Olkhon terrane provide a more complicated scenario of its origin.

As was discovered, each megazone before ca. 480 Ma has its own unique independent history and only after ca. 480 Ma could these units be considered as a building block of the common Olkhon terrane. This suggestion could be clearly demonstrated on the example of two major megazones (Anga–Satyurty and Krestovaya) of the Olkhon terrane.

The Anga–Satyurty megazone consists of gneiss-migmatite rocks, as well as amphibolites, quartzites, marbles and marble mélanges, metagabbro. Granulite-facies rocks are localized within the Chernorud zone of this megazone. The 510–480 Ma magmatic and metamorphic activity in this megazone is marked by 507–498 Ma Chernorud granulites, 485 Ma hypersthene-bearing granites among the Chernorud zone granulites, 489 Ma biotite-hornblende-bearing granites, and 495 Ma quartz syenite. All these granitoids are synfolding and synmetamorphic rocks. Their emplacement was related to sheet-type deformations in the regions. The geochemical characteristics of some granitoids (low Y and Yb contents, fractionated REE patterns) indicate that they were produced in the lower part (field of garnet stability in restite) of the thickened crust. The extra-thickness of this crust was supplied by a previous tectonic event when different fragments of island-arcs and



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back-arc sequences were thrust onto each other. It means that the time interval 510–480 Ma reflects the main accretion event which was responsible for the building of the Anga–Satyurty megazone. In this case the Chernorud granulites (507–498 Ma) might have been formed at the base of this accretional structure.

The Krestovaya megazone consists of metamorphosed volcanics, amphibolite, marbles, quartzites and contain a few large gabbro plutons (Birkhin, Krestovaya, Buguldeika, and others). The 510–480 Ma magmatic activity in this megazone is marked by 492 Ma Tsagan-Zaba metavolcanics and 500 Ma Birkhin gabbroids (Fedorovsky et al., 2010). Tsagan-Zaba volcanic rocks and Birkhin gabbroids, both with clear subduction-related geochemical features and positive Nd(t), belong to common (ca. 500 Ma)

island-arc volcanic-plutonic association. It means that ca. 500 Ma the precursor of this megazone existed as a fragment of an Early Paleozoic island arc.

The first common event (480 – 460 Ma) for both Anga–Satyurty and Krestovaya megazones is represented by the metamorphic processes and emplacement of syn-kinematic granitoids which are widely distributed within the whole Olkhon terrane (Fedorovsky et al., 2005, 2010). Just this event reflects oblique collision of different terranes with the southern margin of the Siberian craton. This collision was accompanied by large-scale shearing. Thus, in general, final collisional stage in the tectonic evolution of the Olkhon terrane has occurred over a time period of about 20 Ma.

References

Gladkochub, D.P., Donskaya, T.V., Wingate, M.T.D., Poller, U., Kröner, A., Fedorovsky, V.S., Mazukabzov, A.M., Todt, W., Pisarevsky, S.A., 2008. Petrology, geochronology, and tectonic implications of c. 500 Ma metamorphic and igneous rocks along the northern margin of the Central-Asian Orogen (Olkhon terrane, Lake Baikal, Siberia). Journal of the Geological Society 165, 235–246.

Fedorovsky, V.S., Donskaya, T.V., Gladkochub, D.P., Khromykh, S.V., Mazukabzov, A.M., Mekhonoshin, A.S., Sklyarov, E.V., Sukhorukov, V.P., Vladimirov, A.G., Volkova, N.I., Yudin, D.S., 2005. The

Ol’khon collision system (Baikal region). In: Sklyarov, E.V. (Ed.), Structural and tectonic correlation across the Central Asia orogenic collage: north-eastern segment (Guidebook and abstract volume of the Siberian Workshop IGCP-480). IEC SB RAS, Irkutsk, 5–76.

Fedorovsky, V.S., Sklyarov, E.V., Izokh, A.E., Kotov, A.B., Lavrenchuk, A.V., Mazukabzov, A.M., 2010. Strike-slip tectonics and subalkaline mafic magmatism in the Early Paleozoic collisional system of the western Baikal region. Russian Geology and Geophysics 51, 534–547.

Holocene paleoclimate reconstruction based on oxygen

isotope composition of plant cellulose

Hafida El Bilali

Carleton University, Department of Earth Sciences, 2125 Herzberg Building, Carleton University, 1125 Colonel

By Drive, Ottawa, Ontario, K1S 5B6, Canada


The timing and magnitude of climate fluctuation vary regionally requiring the use of regional meteorological records. However, long-term trends in regional and global temperatures are influenced by low-frequency events that are difficult to resolve with the short meteorological records and a more complete understanding of intermediate and long-term climate trends and their relationship with short-term variations can only be achieved by turning to the geological record.

Paleoclimate records can be effectively used for detection of climate fluctuation at multi-decadal and longer time-scales, which potentially permits the prediction of future climate. As a case study, I present a paleotemperature reconstruction on a peat

section in eastern Canada throughout the last ~9200 years, utilizing oxygen isotope analysis of plant cellulose, image analysis of peat sediment photographs and X-ray scans, and time-series analysis methods. The results produced the first reconstruction of long-term climate trends and multidecadal–millennial scale cycles in continental eastern Canada. The detected cycles and trends are compared to solar activity fluctuations and discussed in the context of paleoclimate reconstructions in the North Atlantic realm and North America. To test the validity of research methods and proxy records on a more global scale, a comparative second case study has been carried out in a more maritime climate setting on a peat section in Northern Ireland.



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Large igneous provinces and resource exploration:

metals, oil/gas and water

Richard E. Ernsta and Simon M Jowittb

aDept. of Earth Sciences, Carleton University, Ottawa, Ontario, Canada K1S 5B6; Ernst Geosciences, 43

Margrave Avenue, Ottawa, Ontario, Canada K1T 3Y2; and Faculty of Geology and Geography, Tomsk State

University, Tomsk, Russia, 634050

bSchool of Geosciences, Monash University, Melbourne, VIC 3800, Australia


Large Igneous Provinces (LIPs) represent significant reservoirs of energy and metals that can either drive or be incorporated into a variety of differing metallogenic systems and also have significant controls on the maturity of hydrocarbon source rocks, the formation of oil and gas reservoirs, and the development of important aquifer systems. There are five distinct types of relationships between LIPs and these differing systems (ore deposit, hydrocarbon and water), although these relationships partially overlap:

(1) LIP magmas as the primary source of commodities within mineral deposits; this is definitive for orthomagmatic Ni–Cu–(PGE) sulfides (e.g. within the Freetown intrusion of the Gondwana-related 200 Ma CAMP LIP) and LIP events have been strongly linked to the formation of carbonatites, some with REE–Nb–Ta deposits (e.g. Bayan Obo which potentially belongs to either a 920 or 1320 Ma LIP) and diamondiferous kimberlites (e.g. kimberlites associated with the c. 370 Ma Yakutsk-Vilyui LIP of Siberia).

(2) LIP magmas as a provider of energy and/or fluids to enable the formation and sustaining of hydrothermal systems (e.g. epithermal deposits associated with the ca. 180–

160 Ma Chon Aikesilicic LIP (SLIP) and associated with the breakup of Gondwana), as source rocks for the metals within hydrothermal ore deposits (e.g. VMS), as an important influence on the formation of IOCG deposits linked with the silicic components of LIPs or SLIPs, or as a heat source that drove hydrocarbon source rocks to maturation or over-maturation (e.g. associated with the High Arctic LIP).

(3) LIP rocks, particularly sills and dykes, that act as barriers to fluid flow and/or as reaction zones and leading to the formation of mineralization (e.g. orogenic Au) or act as impermeable barriers that control aquifer formation (such as Gondwana breakup-related sills and dykes of the Karoo LIP controlling the location of aquifers within the Karoo sedimentary basin) and act as structural traps for oil and gas resources (e.g. within the North Atlantic Igneous Province).

(4) Weathering of LIP rocks can concentrate elements such as Ni–Co and Al within laterites or bauxites (e.g. forming the Guinea bauxite deposits associated with the CAMP LIP), and lead to additional surficial interactions that causally link oceanic-plateau formation with anoxic events that form important organic-rich



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black shale source rocks for oil and gas (e.g. the Ontong Java or Caribbean-Colombian LIPs).

(5) Indirect links between LIPs and ore deposits have also been proposed, such as far-field tectonic changes caused by LIP events during the plate-tectonic cycle (e.g. orogenic Au associated with far-field effects from the Ontong Java LIP).

In addition to these documented links between LIPs and a variety of resource types, LIP events are critical in reconstructing Precambrian supercontinents and enabling the tracing of metallogenic and hydrocarbon belts between presently separated, but formerly

contiguous, crustal blocks. This clearly demonstrates how our understanding of LIPs, and the processes that affect LIP magmas and rocks, have direct consequences for metal, hydrocarbon and water resource exploration. We provide an overview of how this understanding can be used to identify key relationships and links between LIP events and the formation of these various deposits or resources in the geological record and, as such, can be used to enhance exploration strategies and our knowledge of the plate tectonic history of the Earth.

Reflection of central Asia block structure in modern

geophysical fields

Yuriy Gatinskya, Tatiana Prokhorovab

aVernadsky State Geological Museum RAS, Moscow, Russian Federation bInstitute of Earthquake Prediction Theory and Mathematical Geophysics RAS, Moscow, Russian Federation


During 2004–2009 the authors together with Yu. Tyupkin, D. Rundquist, and G. Vladova worked out a problem of up-to-date geodynamic heterogeneity of the Eurasian continent with establishing the north Eurasian lithosphere plate and some transit zones between it and neighboring plates. Central Asian and east Asian transit zones were distinguished at boundaries with Indian, Pacific, and Philippine plates. The zones consist of numerous blocks limited by active faults, and, what is more, the maximal tectonic activity coincides with interblock zones (Fig. 1). Since 2009 we fulfilled the closer definition of block boundaries and interblock zones in central Asia. The majority of active faults and epicenters of the strongest earthquakes coincide with them, so their detailed investigation and correlation with different geophysical fields are important for establishing the level of the seismic activity in this region.

In the seismic energy field the maximal volume of energy is released in plate boundaries and interblock zones of the central Asian transit zone (Fig. 2). In the field of up-to-date tectonic stress the compression distinctly predominates in this transit zone and changes partly on extension and slipping with extension in the east Asian zone. Such change can be most distinctly seen west and east of the south edge of Lake Baikal. Transpression predominates in the west in Sayan Mountains, where NE thrusts are developed, proved by orientation of stress axes.

East from there in the Tunka Trough left-lateral strike-slips predominates, which is clearly seen in the displacement of streamlet thalwegs and left-lateral movement along the Main Sayan Fault after earthquake mechanisms. Further east, strike-slips are replaced by normal faults in the flanks of the Baikal Rift and Barguzin depression, which is also included in this rift system. The latter dislocations already correspond to the transtension tectonic regime [Sankov, et al., 2002; Gatinsky et al., 2009, 2011; Parfeevets, and Sankov, 2012].

High positive anomalies of the magnetic field (up to +50–+100 nT) characterize the greater part of the interblock zones and large faults limit them. The gravitational field of the most part of central Asia in the Bouguer reduction is characterized by negative values up to –50–150 mGal. The distinct gravitational lineament crosses a significant part of the continent from the Bacbo Bay to the Okhotsk Sea coast in the NNE direction with changing of above mentioned negative values by more positive ones in the east. This change is connected with the sharp decrease of the continental crust thickness.

Heat-flow values increase up to 80–100 μW/m-2 and more in interblock zones, which are situated at the boundaries of Hangay, Amurian, Tibet, and Tarim blocks as well as in some inner continental rifts. But besides that we can see increasing heat-flow values underneath the inner



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part of some blocks: Tienshan (up to 100–140 μW/m-2), Hangay (up to 120–190 μW/m-2), Amurian (up to 80–100 μW/m-2), SE China (up to 120–190 μW/m-2), where they often coincide with areas of S-velocities slowing-down. This increase supposedly corresponds to the influence of mantle plumes on the lithosphere of central Asia. One of these plumes can be selected under Hangay and Sayan blocks at the depth of 100–150 km. Here the thickness of the lithosphere decreases down to 70–50 km, and the temperature at the depth of 50 km can be about 1000–1200 oC according to correlation based on He3/He4 isotopes [Lysak, 2009; Duchkov et al., 2010]. At greater depth down to 200–300 km this plume moves east under the Lake Baikal and Transbaikalia, where intensive Neogene and Quaternary basalt volcanism can be connected with it [Grachev, 2000]. Heat-flow anomalies under Qilian and east Qinlin blocks can be supposedly connected with the existence a low velocity channel of the asthenosphere material at the depth of 125–200 km [Zhang et al., 2011]. The crust thickness changes in central Asia from 25–30 km in the east up to 50–75 km in the west under Tibet and neighboring blocks. The lithosphere thickness changes in the same direction from 60–80 km up to 120–150 km, but it decreases up to 100 km and less under inner continental rifts coinciding with interblock zones.

The direction of the P- and S-wave anisotropy shows the coupling deformation of the lithosphere, upper mantle and crust within greater part of the region. Differently directed vectors of horizontal displacement are established in the crust and upper mantle only east of the east Himalayan syntax indicating the decoupling of these layers under the influence of the Hindustan–Asia collision and ‘a threshold’ of the SE China thick-lithosphere in its boundary with Tibet. The sharp increase in the upper crust east of the Longmen Shan Fault in SE China Block is supposedly connected with the flowing and uprising of the plastic material, composing the lower and middle crust, west under Bayan Har and Tibet [Li et al., 2011; Zhang et al., 2009]. Because of that the upper crust tears away and moves independently east along the more plastic middle and lower crust [Flesch et al., 2005; Shen et al., 2005]. This process is proved by the existing layers of high electric

conductivity in the south Tibet crust at 20–45 km depth, which supposedly corresponds to the partial melting of the crustal material [Li et al., 2003; Solon et al., 2005; Oreshin et al., 2011]. The data shows the direct connection of interblock zones with crust thickness gradients, especially in boundaries of Amurian, Ordos, Bayan Har and Tibet’s blocks.

Studying the connection of the central Asia block structure with different geophysical fields reveals that the majority of the interblock zones coincide with increased anomalies of the seismic energy release, magnetic fields and often with the high heat-flow, as well as with gradients of the crust and mantle thickness. These zones are sometimes situated within areas of intensive delamination of the crust and whole lithosphere with differently directed motions of their layers. All these peculiarities bring about the high up-to-date geodynamic activity of interblock zones including development within them of epicenters of the most catastrophic earthquakes. The following interblock zones of central Asia can be mentioned as the most seismically active: at boundaries of the Tienshan Block in Kazakhstan, Kirghizia and NW part of the Xinjiang Province of China (the volume of the specific energy is 2.88–3.97 x 1013 J); at boundaries of Hangay and Amurian blocks in the Baikal region in Russia and Mongolia (2.9 x 1012 J); at north and south boundaries of the Pamirs in Tajikistan and Afghanistan (≥1.44 x 1013 J); at the boundary between the Himalayas Block and Indian Plate in Tibet and north India (9.51 x 1012

J); and at all boundaries of the Bayan Har Block in China (3.99 x 1013–9.25 x 1016 J). The majority of catastrophic earthquakes took place within the above mentioned interblock zones during the past centuries. This emphasizes the need for a detailed study of the seismicity and geodynamics of interblock zones with assimilation of data from international catalogs of earthquakes, analysis of active faults, geophysical fields, and GPS vectors, as well as deep structures of territories.

The main causes of the high inner-continental seismicity development in interblock zones is connected with the continuation of the collision slabs deep under Tibet and the Pamirs, the intensive displacement of rheologically layered crust horizons along faults under the influence of collision processes, as at the SE

29

boundary of the Bayan Har Block, existence of the large lithospheric inhomogeneity including mantle plumes as in Sayan, Hangay, and NW part of the Amurian Block. The dependence of the seismic activity increasing from the relatively long seismic gap was established for the SE boundary of the Bayan Har Block [Gatinsky et al., 2008, 2009, 2011; Gatinsky, and Prokhorova, 2014], where

catastrophic earthquakes are repeated every five years after nearly 40 year’s seismic gap. So the detailed investigation of the geological structure of the interblock zone’s geophysical fields and seismicity has great significance for the prediction of catastrophic earthquakes and identification of areas of highly hazardous seismic events.

Fig. 1. Up-to-date block structure of central Asia and adjacent territories. Red lines – active faults after [Xu and

Deng, 1996; Trifonov et al., 2002; Yin, 2010; Sherman et al., 2011], blue lines – rivers. Boundaries: dark blue –

lithosphere plates, green – blocks, yellow – interblock zones; violet – boundary between central Asian and east

Asian transit zones; light blue – supposed boundaries [Gatinsky et al., 2005, 2009]. Blocks (numerals in figure):

(1) Altai, (2) west Mongolian, (3) Ebi Nur, (4) south Gobi, (5) Tienshan, (6) Pamirs, (7) west Kunlun, (8) west

Qinlin, (9) Qilian, (10) Taihangshan, (11) south Tibet, (12) Kam Dian, (13) Ryukyu – central Honshu, (14)

Andaman’s – west Myanmar, (15) north Luzon. Note, active faults emphasize the selection of majority blocks.

30

Fig. 2. The block structure of central Asia in the seismic energy field. Each increment of the color intensity

corresponds to increasing seismic energy volume on 1x101 or 1x10-1 J. Some energy values are shown in the

scheme in joules. Epicentres: circle: instrumental (NEIC), stars: historical from VIII to XIX century [Xu, and Deng,

1996]. Earthquakes magnitude: violet: 6.0–6.9, black: 7.0–7.9, red: ≥ 8.0. Arrows: red: experimental ITRF vectors

of horizontal and blue: of vertical displacement, black: model vectors with respect to stable Eurasia. Boundaries,

not signed blocks and names of towns see in Figure 1.

Late Mesozoic to early Paleogene uplift and exhumation

processes of the Beishan, southern CAOB: preliminary

apatite fission track results

Gillespie, Jack.a, Glorie, Stijn.a, Zhang, Zhiyong.b, Xiao, Wenjiao.b, Collins, Alan.a

aCentre for Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, The

University of Adelaide, Adelaide, Australia bDivision of Tethys Research Centre, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing,

China

The Central Asian Orogenic Belt (CAOB) is composed of a series of orogenic collages which progressively accreted against the southern margin of the Siberian Craton from 1000 Ma-250 Ma (Windley et al. 2007). The Beishan Orogenic Collage (BOC) is located in the south of the CAOB and is flanked by the terminal sutures of the CAOB, the Tianshan and Solonker sutures, which record the closure and final consumption of the Paleoasian Ocean in the end-Permian to Mid-Triassic (Xiao et al. 2009).

This study aims to constrain the low temperature thermochronology of the BOC, expanding on similar work done in the vicinity such as in the Tianshan (Glorie et al. 2011, De Grave et al. 2013). Previous studies in the Beishan have provided 40Ar/39Ar constraints on ductile shearing in the Xingxingxia fault that occurred at 240-235 Ma, interpreted to be post-orogenic strike-slip faulting which occurred after the amalgamation of the CAOB (Wang et al. 2010).The results of our thermochronological work will refine existing low-temperature thermal history models and provide insight into the intracontinental exhumation of the BOC. Comparison of our results with those from neighbouring regions will provide a more complete understanding of the thermo-tectonic

history of the southern CAOB. Apatite fission track (AFT) analysis on 15

samples along a roughly North-South transect through the BOC suggests evidence for three distinct phases of exhumation during (1) the Late Triassic - Early Jurassic, (2) Early Cretaceous and (3) Late Cretaceous - Early Paleogene. Samples at the northern edge of the BOC (Xingxingxia fault zone) reveal a more profound Late Cretaceous - Early Paleogene signal and a weaker Late Triassic - Early Jurassic signal than those in the middle of the sampling transect (in the vicinity of Liuyuan). In contrast, samples from the southern margin of the BOC (Dunhuang region) show no evidence for post-early Cretaceous exhumation but record a much larger early Jurassic component. A potential explanation for this discrepancy lies in the presence of the Xingxingxia fault in the northern BOC which seems to have undergone repeated reactivation throughout the Mesozoic, exposing deeper exhumed sections of the BOC. The fault may thus have acted as a control on exhumation in the region. The samples at the southern BOC margin however are located at the edge of the Dunhuang block which is thought to form part of the tectonically relatively stable Tarim Craton. This interpretation may explain why the



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southern BOC is less susceptible to later reactivation due to the lack of inherited structures such as sutures from the closure of oceanic basins.

This pattern is consistent with results from elsewhere in the CAOB such as in the Tianshan and the Altai (e.g. Glorie et al. 2011, Glorie et al. 2012), where widespread exhumation in the Early Cretaceous was followed by localised exhumation in the Late Cretaceous and Early

Paleogene, focussed around reactivated structures.

Our results indicate that the Triassic - early Jurassic and Cretaceous - early Paleogene exhumation events in Central Asia were more widespread than previously anticipated, extending to the northern margin of the Tarim Craton. This observation hence refines the existing tectonic history models for Central Asia.

Tectonics of the Transbaikalian segment of the central

Asian orogenic belt

D.P. Gladkochuba, T.V. Donskayab, A.M. Mazukabzovc

Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences,

128 Lermontov Str., Irkutsk 664033, Russia

A significant portion of the continental crust of northern Eurasia is thought to have formed during the evolution of the Central Asian Orogenic Belt (CAOB) by accretion of continental and subduction-related terranes. Records of this event are well preserved within southern Siberia. This area includes the southern part of the Siberian craton and adjacent terranes of the CAOB. The synthesis of geological, geochronological and geochemical data of the Neoproterozoic–Mesozoic intrusions, lavas and sediments of this area, allows us to propose the following scenario of geodynamic evolution for this segment of northern Eurasia:

(1) In the late Neoproterozoic (Ediacaran) the Siberian craton was detached from Rodinia. A number of island arcs and back-arc basins were formed within the Paleo-Asian Ocean, which was open as a result of Rodinia breakup (Gladkochub et al., 2013). The signatures of these processes are well represented by relicts of such terranes.

(2) The late Cambrian–Early Ordovician was marked by collision of numerous terranes (microcontinents, fragments of island arcs and back-arc basins etc.) onto the southern margin of the Siberian craton. High-grade metamorphic terranes were generated in the contact zone between the craton and accreted terranes. This event reflects the early stage of the Paleo-Asian Ocean closure and the beginning of the building of the CAOB.

(3) The late Ordovician and Silurian within

the study area were not marked by significant tectonic and igneous activities, excepting for the latest accretion-collision events which had begun in the Cambrian and early Ordovician.

(4) Since the late Paleozoic the development of the Transbaikalian segment of CAOB was directly related to the evolution of the Mongol-Okhotsk Ocean where the late Silurian–Middle Devonian terrigenous and carbonate sediments were deposited.

(5) In the middle Devonian, the subduction of oceanic lithosphere of the Mongol-Okhotsk Ocean began at a gentle angle under the Siberian continent. It led to slab stagnation and decrease in the subduction rate. It caused a dispersed extension and accelerated collapse of the early Paleozoic orogen and the formation of the Tocher trough of Transbaikalia. The slab stagnation resulted in the increase in the density and angle of the dipping slab, which finally led to the change of the extension regime by the compression.

(6) The early–late Carboniferous is characterized by compression, metamorphism and deformations, which have resulted in the closure of a Tocher trough and thickening of continental crust. Mantle input into the lower crust caused melting of the metamorphic protoliths and produced the autochthonous biotite granites of the Angara-Vitim batholith.

(7) Late Carboniferous–early Permian stage was related to the destruction of the subduction slab and roll-back toward the ocean. It caused



Abstract Volume


34

the extension of continental lithosphere and the mantle input into the continental crust. The allochthonous granitoids of the Angara-Vitim batholith and the magmatic rocks of the Western Transbaikalian belt were formed during this stage (Jahn et al., 2009).

(8) Late Permian–late Triassic is characterized by the normal-angle subduction of the Mongol-Okhotsk oceanic crust which caused emplacement of various types of intrusions (Khangay and Khentey batholiths) and volcanics. The majority of early Mesozoic magmatic rocks of this area were produced within the active continental margin by subduction-related sources with hot-spot influence as well (Donskaya et al., 2013).

(9) During the Jurassic significant decrease in igneous activity could be noted in Transbaikalia, northern and central Mongolia. We explain these phenomena as due to the completion of the Mongol-Okhotsk oceanic crust subduction beneath Siberia in this area. The final closure of this ocean in its western part took place in late Jurassic–early Cretaceous.

(10) Early Cretaceous was marked by the closure of the Mongol-Okhotsk Ocean, large-scale intra-plate extension and exhumation of numerous metamorphic core complexes (Wang et al., 2012). Since the late Mesozoic the Transbaikalian segment of CAOB developed as a stable intra-continental area.

References

Donskaya Т.V., Gladkochub D.P., Mazukabzov A.M., Ivanov A.V. Late Paleozoic – Mesozoic subduction-related magmatism at the southern margin of the Siberian continent and the 150 million-year history of the Mongol-Okhotsk Ocean // Journal of Asian Earth Sciences, 2013. V. 62. P. 79-97.

Gladkochub D.P., Stanevich A.M., Mazukabzov A.M., Donskaya T.V., Pisarevskii S.A., Nicoll G., Motova Z.L., Kornilova T.A. Early evolution of the Paleoasian ocean: LA-ICP-MS dating of detrital zircon from Late Precambrian sequences on the southern flank of the Siberian craton. Russian Geology and

Geophysics. 2013. V 54. P. 1150–1163 Jahn, B.M., Litvinovsky, B.A., Zanvilevich, A.N.,

Reichow, M., 2009. Peralkaline granitoid magmatism in the Mongolian–Transbaikalian Belt: Evolution, petrogenesis and tectonic significance. Lithos 113, 521–539.

Wang T., Guo L., Zheng J., Donskaya T., Gladkochub D., Zeng L., Li J., Wang Y., Mazukabzov A. Timing and processes of late Mesozoic mid-lower-crustal extension in

continental NE Asia and implications for the tectonic setting of the destruction of the North China Craton: Mainly constrained by zircon U-Pb ages from metamorphic core complexes. Lithos. 2012. V. 154. P. 315-345.



Abstract Volume


Meso-Cenozoic exhumation history of Central Asia

recorded by fission track and U-Th/He

thermochronology: examples from the Kyrgyz Tian Shan,

Russian Altai-Sayan and Chinese Beishan

Glorie Stijna, De Grave Johanb, Buslov Mikhaelc, Gillespie Jacka, Zhang Zhiyongd,

Xiao Wenjiaod

aCentre for Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, The

University of Adelaide, Adelaide, Australia bDept. Geology & Soil Science, MINPET Group, Ghent University, 281-S8 Krijgslaan, Ghent, Belgium cInstitute of Geology and Mineralogy, Siberian RAS,pr. AkademikaKoptyuga 3, Novosibirsk, Russia dDivision of Tethys Research Centre, Institute of Geology and Geophysics, CAS, Beijing, China

Central Asia represents the world`s largest and most active intracontinental deformation zone between the Tibetan plateau and the Siberian craton. This region was reactivated several times during its geological history in response to collisions at the distant plate margins and hence represents an excellent natural laboratory to investigate the timing and spatial distribution of intracontinental deformation. We present multi-method thermochronological results (apatite and titanite fission track; and apatite and zircon U-Th-Sm/He data) to elucidate the thermal history of the Tian Shan, Altai-Sayan and Beishan Mountain Ranges. It was found that most of the Central Asian rock exposures surfaced during the Middle–late Mesozoic and only it’s dissecting fault zones record evidence for subsequent Cenozoic deformation.

Besides the occurrence of some older, Early Mesozoic geomorphic features (such as internally drained plateaus or old erosion surfaces), most of the current relief is related with an important phase of Late Jurassic–Early Cretaceous uplift and exhumation that has been documented throughout most of Central Asia. This episode of relatively slow cooling and exhumation is thought to be associated with collisions of Gondwana-derived, Cimmerian Blocks to Eurasia in the South and to the closure of the Mongol-Okhotsk Ocean to the Northeast (De Grave et al., 2011; 2013).

Major fault systems within the Tian Shan record Cenozoic episodes of fault-induced rapid exhumation during the Early Palaeogene (~60-45 Ma) and Late Oligocene (~30-25 Ma) to Miocene (~10-8 Ma)(Glorie et al., 2011; De Grave et al. 2013). The first major pulses of

36

these fault-reactivation events coincide remarkably well with the `soft` (~50 Ma) and `hard` (~25 Ma) collisions of India with Eurasia, arguing that the India–Eurasian convergence is the main driving force behind Cenozoic mountain building in the Tian Shan.

The Beishan shows little evidence for post-Cretaceous exhumation and its current relief mainly formed during the Late Jurassic–Cretaceous. This is slightly younger than previously suggested. Furthermore, few Latest Cretaceous–Early Palaeogene fission track ages may hint towards a younger brittle reactivation stage along its main fault-systems as well (Gillespie et al., 2014).

For the Altai and Sayan Ranges, rapid fault-induced exhumation occurred during the Late Cretaceous–Early Palaeogene (~90-60 Ma), which is thought to be a far-field response to the collapse of the Mongol-Okhotsk orogen between

the Siberian and North China–Mongolian continental blocks (Glorie et al., 2012; De Grave et al., 2014). Furthermore, the main East-West striking structural fabric (the Sayan fault system) documents Late Cretaceous–Early Palaeogene rapid exhumation over its entire length, from the Altai and Sayan Ranges to the Baikal region, suggesting that the exhumation of the Altai and the initiation of rifting in the Baikal region are likely interconnected. After a long period of subsequent thermal stability, the Altai and Sayan region were subjected to a renewed phase of Plio-Pleistocene (~3-1 Ma) reactivation (Glorie et al., 2012; De Grave et al., 2014), which is likely related with the ongoing India–Eurasia convergence that induced fault-reactivation much later as documented for the Tian Shan region.

References

De Grave, J., Glorie, S., Buslov, M.M., Izmer, A., Fournier-Carrie, A., Elburg, M., Batalev, V.Yu.,Vanhaeke, F., Van den haute, P. (2011). The thermo-tectonic history of the Song-Kul Plateau, Kyrgyz Tien Shan: constraints by apatite and titanite thermochronometry and zircon U/Pb dating. Gondwana Research, 20 (4), 745-763.

De Grave, J., Glorie, S., Buslov, M.M., Stockli, D.F., McWilliams, M.O., Batalev, V.Yu, Van den haute, P. (2013).Thermo-tectonic history of the Issyk-Kul basement (Kyrgyz Northern Tien Shan, Central Asia).Gondwana Research, 23 (3), 998-1020.

De Grave, J., De Pelsmaeker, E., Zhimulev, F.I., Glorie, S., Buslov, M.M., Van den haute, P. (2014).Meso-Cenozoic building of the northern Central Asian Orogenic Belt: thermotectonic history of the Tuva region

(West Sayan, Altai, Tannu Ola, Sengilen Ranges).

Tectonophysics 621, 44-59. Glorie, S., De Grave, J., Buslov, M.M.,

Zhimulev, F.I., Stockli, D.F., Batalev, V., Izmer, A., Van den haute, P., Vanhaecke, F., Elburg, M. (2011). Tectonic history of the Kyrgyz South Tien Shan (Atbashi-Inylchek) suture zone: the role of inherited structures during deformation-propagation. Tectonics, 30, TC6016.

Glorie, S., De Grave, J., Buslov, M.M., Zhimulev, F.I., Van den haute, P., Elburg, M.A. (2012). Structural control on Meso-Cenozoic tectonic reactivation and denudation in the Siberian Altai: Insights from multi-method thermochronometry. Tectonophysics, 544-545, 75-92.

Gillespie, J., Glorie, S., Zhang, Z., Xiao, W., Collins, A. (2014). Late Mesozoic uplift and exhumation of the Beishan: preliminary apatite fission track results. This Abstract Volume.



Abstract Volume


The Jiaodong gold deposits, eastern China: A global

anomaly of Phanerozoic gold in Precambrian rocks

Richard J.Goldfarba,b, M. Santoshb

a U.S. Geological Survey, Box 25046, Denver Federal Center, Denver, CO 80225 b State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences,

Beijing 100083, China

The Early Cretaceous gold deposits of the Jiaodong Peninsula, eastern China, define the country’s largest gold province with a pre-mining endowment >3000 t Au and an estimated annual production of 30-50 t Au. The majority of this gold was deposited over a brief period between ca. 126 and 120 Ma within terranes of Precambrian high-grade metamorphic rocks, which are located on both sides of the Triassic suture between rocks of the North and South China blocks. More than two-thirds of the exposed area of these terranes is characterized by felsic to intermediate calc-alkaline intrusions that were emplaced into basement rocks at mainly ca. 165-150 Ma and 130-123 Ma.

The vein and disseminated ores are hosted by NE- to NNE-trending brittle normal faults that parallel the margins of the Middle to Later Jurassic, deeply emplaced, lower crustal melt granites. There is no spatial association between the younger Early Cretaceous intrusions and the gold deposits, despite a temporal overlap. The gold deposits are sited along the faults for many tens of kilometers and the larger ore bodies are associated with dilational jogs. These faults have been interpreted as subsidiary faults to the continental-scale Tan-Lu fault system, which is located about 20-30 km west of some of the largest gold deposits. The ore-hosting structures developed as ductile thrust faults during early Mesozoic convergent deformation; they were

subsequently reactivated during Yanshanian intracontinental extensional deformation and associated gold formation. The ores were deposited by aqueous-carbonic, 18O-rich, low salinity fluids at about 250-350oC and 3-8 km depth during the unroofing of the various igneous bodies. However, unlike other structurally-controlled gold deposits formed from such a fluid type, the source of the fluids and metals could not have been the country rocks of the host terranes because these components would have been lost from the crustal rocks during regional metamorphism more than two billion years earlier.

Important modifications to the commonly accepted ore genesis model for Phanerozoic orogenic gold deposits, in which ores formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens, is required based upon the setting of the Jiaodong gold deposits. The deposit distribution along major fault zones and a mineralization style with little chemical zoning over great vertical extent is atypical of ores formed from nearby magmatism. Fluid focusing during some type of sub-crustal event is required, which must relate to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific subduction, and/or seismicity along the continental-scale Tan-Lu fault (Goldfarb and Santosh, 2014). Gold formation post-dated the

38

initial delamination of the subcontinental lithospheric mantle, Yanshanian deformation, and Jurassic magmatism in the Jiaodong region by 30-50 m.y. One possible source for the ore-forming fluids and the metals would have been the ca. 125 Ma dehydration, decarbonization, and desulfidation of subducting sediment and/or the underlying basalt of the paleo-Pacific plate, particularly if a relatively low slab angle characterized late Mesozoic subduction. Fluids

would have been channeled into the continental-scale Tan-Lu fault system, which is rooted in the asthenospheric mantle below the greatly thinned lithosphere (Fig. 1). Alternatively, released fluid and metal may have been temporarily stored in the fertilized mantle wedge for tens of millions of years and subsequently released into the Tan-Lu fault system by some type of heating event in the wedge at ca. 125 Ma (Fig. 1).

Fig. 1 Cartoon showing the most permissive scenarios for Early Cretaceous gold formation in the Jiaodong area.

References

Goldfarb, R.J., and Santosh, M., 2014, The dilemma of the Jiaodong gold deposits: Are they unique? Geoscience Frontiers, v. 5, p. 139-154.



Abstract Volume


Importance of craton margins and other lithosphere

boundaries for gold and other metal exploration

David Ian Groves

Centre for Exploration Targeting, UWA, Nedlands, Western Australia.

China University of Geosciences, Beijing, China

Available statistics on discovery and resource inventories for metals indicate that discovery rates are declining, the cost per discovery is rising steeply, and it takes an increasing amount of time to bring mines into production. This is particularly true for the gold exploration industry. The current exploration and mining industry structure makes this situation difficult to redress. Several studies have shown that the industry as an entity is a low base-rate situation, with close to zero return. As economic geologists, there is little we can do to influence the required changes to the overall structure and philosophy of an industry driven by business rather than geological principles. What we can do is influence the nature of greenfields exploration, necessary for the next group of significant discoveries. As the oil industry has done over the past several decades, we need to increase the percentage of discovery success by significantly decreasing the number of low-potential targets that are drilled, after careful consideration of their economic potential in terms of a regional geological framework. This abstract examines the geological principles behind this type of regional assessment, emphasising the importance of exploration in suitable tectonic and lithospheric settings, particularly adjacent to craton margins and other lithosphere boundaries. It places emphasis on gold deposits as these are the author’s main expertise.

Most difficulties in life are caused by an

inability to view critical issues at an appropriately large scale: to “see the wood for the trees”. Arguably, economic geology also suffers from the same problem. As a profession, there is a tendency to view and classify deposit types at the deposit scale, despite an increasing emphasis on a hierarchical mineral systems approach from supercontinent through province to district to deposit scales. As highly anomalous metal concentrations, mineral deposits are not simply formed in specific locations at specific times due to deposit-scale processes, but due to tectonic processes in the supercontinent cycle in an evolving Earth. This is recognised when the exploration process is viewed as a temporally staged process at increasingly smaller scales. Each exploration target, commonly acquired for reasons outside this rigorous framework, should thus be viewed in terms of its larger scale tectonic and temporal setting to access its true potential.

Orogenic Gold, Intrusion Related Gold (IRGD), Carlin-type Gold, and Iron-Oxide Copper-Gold (IOCG) deposits are classified as separate deposit types on the basis of their deposit-scale geological and genetic characteristics, such as structural style, host rocks, wall-rock alteration, metal associations, fluid characteristics, and PT conditions of formation. At this scale, some deposits have shared characteristics, but contrasts are more common than similarities, and different deposit-scale genetic processes are invoked for their

40

formation. When the deposit styles are viewed in terms of the supercontinent cycle, they again formed at different times, but, importantly, each formed at very specific times within that cycle, suggesting that each has a specific tectonic control.

When the driving forces for these deposits are viewed in terms of such a crustal to lithosphere to mantle scale, surprisingly they have many parameters in common. This is highlighted in recent reviews of IRGD, Carlin-style (with Bingham Canyon porphyry Cu-Au) and IOCG deposits, where all are shown as forming above metasomatised lithosphere from fluid connected to mixed basic to felsic alkaline or sub-alkaline intrusions that formed in sub-MOHO magma chambers. Although in different settings, arc-related economic porphyry Cu-Au deposits appear to be connected to intrusions derived from magmas ponded below the MOHO during arc compression. Although the source of orogenic gold deposits is still hotly debated, magmas intruding hosting supracrustal sequences are considered highly unlikely as a direct source of major deposits. However, recent research shows that, for at least the Jiaodong deposits of China, the source of ore fluids must be derived from below supracrustal rocks of the continental crust, the most commonly suggested fluid source, from either the subduction slab, with overlying oceanic sediments, or the lithosphere below. A deep source is also implied by the common spatial association of orogenic gold deposits with lamprophyre dykes. Hence, the source region for orogenic gold deposits may be spatially adjacent to that of the other gold deposit types, but active at a different time in the orogenic cycle.

These lithosphere-scale genetic commonalities strongly suggest that the deposits have similarities in tectonic settings despite their deposit-scale contrasts.

As expected from their similar lithosphere-scale genetic models, IRGDs, Carlin-type (and Bingham Canyon), and IOCG deposits all show

spatial associations with craton margins, defined by geological and geophysical parameters, where previous subduction events have enriched the lithosphere with incompatible elements and metals during metasomatism. More sophisticated analysis shows the importance of these margins, and other discontinuities not so readily discerned by traditional analysis, as lithosphere boundaries that control many ore deposits, including these gold deposit types. The Jiaodong orogenic gold deposits show clear spatial relationships to such lithosphere boundaries around the margins of the North China Craton, and there is emerging evidence that other world-class orogenic gold provinces, such as those in the Yilgarn Craton of Western Australia, extend along or adjacent to such boundaries that predate the formation of the gold provinces.

It follows from the discussion above that each district to deposit-scale exploration target, instead of being viewed in isolation, should be tracked back up scale to determine its relative value in terms of its timing within the context of the supercontinent cycle for its specific deposit type and its tectonic setting as a generic factor. Specifically, craton margins and other lithosphere boundaries should be buffered to determine the probability that any specific target has the potential to lie within a world-class gold province. Using this screening process, the number of preliminary targets selected for more extensive and expensive exploration drilling on the basis of local anomalism should significantly decline.

A benefit of the approach is that exploration is then focussed along lithosphere boundaries where other magmatic ore deposit types (e.g., Intrusion-hosted Ni-Cu deposits, Carbonatite-hosted REE and Cu-Fe-P deposits) also formed, or further deposit styles such as Volcanogenic Massive Sulfides may have been trapped during accretion, leading to discovery of deposit types other than gold.



Abstract Volume


Late Mesozoic intracontinental orogeny in Qinling

orogen, central China

Anlin Guo, Guowei Zhang *, Shunyou Cheng, Anping Yao

State Key Laboratory of Continental Dynamics/Department of Geology, Northwest University, Xian

710069, China

The Qinling orogen in a tectonic framework of ‘three-plate with two suture zones’ in central China has experienced prolonged and multiphase tectonic evolution and is a typical continental composite orogen.

The Early Mesozoic Indosinian orogeny built up the main framework of the China continent through the collision between the North and South China plates. After this orogeny, a new Late Mesozoic intracontinental orogeny (which peaked at Late Jurassic and Early Cretaceous) followed.

1. End of plate-driven orogeny The Early Mesozoic Indosinian collisional

orogeny represents the last orogeny driven by plate tectonics in Qinling. The evidence for the end of the orogeny includes: 1) the intrusion of post-collision granites. The plutons exhibit geochemistry of post-collisional granite and some are I-A type granites and rapakivi (217-200 Ma). 2) The formation of Late Triassic and Early-Middle Jurassic (T3-J1-2) faulted basins in Qinling.

2. Late Mesozoic intracontinental orogeny After the post-collisional orogeny, Qinling

commenced its Late Mesozoic intracontinental orogeny which peaked at Late Jurassic and Early Cretaceous (J3-K1). The orogeny was characterized by large-scale thrusting and associated uplifting, deformation and metamorphism of the T3-J1-2 basins, granitic magmatism and related polymetallic

mineralization. 3. Large-scale thrusting and quick uplifting

in Qinling In the J3-K1, the large-scale thrust directing

the foreland and hinterland of the Indosinian Qinling orogen were developed along preexisting major faults and southern and northern boundary faults. The southward thrusting involved North Qinling and South Qinling, from north to south forming the Luonan-Luanchuan-Fangcheng, Wushan-Shangxian-Danfeng-Shucheng and North Qinling thick-skinned imbrication thrust systems, and South Qinling-Dabashan thrust system, while the northwards thrusting mainly occurred in the area along the northern margin. As a result, the cross-section of the Qinling orogen shows an asymmetric flower-like structure comprising the four thrust systems with the alkaline magmatism developed in the center of the structure.

During the thrusting, the sedimentary rocks in the T3-J1-2 faulted basins were subjected to deformation and low greenschist facies metamorphism, and some tectonic slices were thrust onto the basins.

The study of cooling and uplifting history of the Qinling orogen, using various thermal chronological methods (Ar/Ar, FT and U-Th/He), has indicated that the quick uplift and cooling in different parts of Qinling mostly occurred between 150 Ma to 90 Ma. These ages

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yielded by samples from magmatic bodies and faults completely coincide with the large-scale thrusting in Qinling.

4. Intracontinental magmatism and related mineralization

The Qinling intracontinental magmatism is characterized by intrusion of ~158–100 Ma granitoids. The plutons are mainly distributed in East Qinling and the Tongbai-Dabieshan area. The granitoids in East Qinling were mainly emplaced in the former southern North China Block (NCB) and North Qinling, and a few in South Qinling close to the Shangdan fault zone.

Spatially, the granitoids form the southern and northern zones approximately parallel to each other on both sides of the Luonan-Luanchuan fault. The southern zone consists mainly of batholiths that intruded the Proterozoic-Early Paleozoic trench-arc-basin system. The northern zone is chiefly composed of more than 60 granite porphyry plutons exposed in the basement and cover of the NCB.

The granitoids geochemically belong to high-K calc-alkaline to shoshonitic series and I, I-A and A-type granites with metaluminous to peraluminous features. These granitoids have evolved Sr–Nd isotopic compositions with 87Sr/86Sr (t) = 0.70455 to 0.71566 and εNd (t) = -18.7 to -3.8. The value of TDM varies with the locality where the pluton intruded.

The Late Mesozoic granitic magmatism plays a major role in the related polymetallic (Mo, Cu, Au, Sb) mineralization. The ore deposits have the same ages of the associated plutons and the metallurgic materials possess the same origin like the plutons.

5. Discussion on the origin of Qinling intracontinental orogeny

The synthetic analysis of the contemporaneous (J3-K1) regional geology in the

surroundings suggests that the Qinling intracontinental orogeny was not operated by plate tectonics or influenced by far field effect of plate tectonics, and instead it was probably originated from non-plate tectonics mechanism.

The major arguments are as follows: 1) When the orogeny occurred, there was no collision between the Indian plate and Eurasian plate and in turn no uplift of the Qinghai-Tibet plateau; 2) The Paleopacific/Izanagi plate did not subduct underneath southeast Asian continent, instead it moved northeastward, which was perpendicular to the Late Mesozoic Qinling orogen; 3) The far field effect possibly induced by the contemporaneous Mongolia-Okhotsk orogeny through subduction and collision could be absorbed and weakened by the contraction of the Yanshan intracontinental orogenic processes and/or ruled out by the near N-S trending fold structure formed to the south of the Yanshan orogen in NCB (e.g., the Shanxi geanticline).

According to the two magnetotelluric sounding (MTs) transects of Qinling, the lithospheres of both the NCB and South China Block (SCB) have been subducting underneath the Qinling. The subduction of the NCB is at a steep angle (≥50°) and has short horizontal distance which caused the formation of the northern marginal thrust tectonic system, whereas the subduction of SCB is at a smaller angle (20°) and the horizontal subduction distance is about 70–100 km which resulted in a much broader south-directed thrust zone in Qinling. It has been noted that the magmatism was mainly associated with the subduction of the NCB rather than the SCB, similar to the relationship between the angle of a descending slab and magmatism.



Abstract Volume


Fluid inclusion constraints on gold deposition in the

Taishang deposit, Jiaodong Peninsula, China

Linnan Guoa, Liqiang Yanga* and Zhongliang Wanga

aState Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences,

Beijing 100083, China *Corresponding author e-mail: [email protected]

1 Geological Setting The Taishang super-large altered rock type

gold deposit is located in the western part of the Jiaodong gold metallogenic province. The lode-gold ore bodies are hosted in the Late Jurassic Linglong-type biotite granite and controlled by Potouqing fault. Gold occurs mainly in pyrite- and polysulfide–quartz vein/veinlet stockworks.

Three mineralization stages were identified, which are pyrite-quartz-sericite (early stage), pyrite- and polysulfide-quartz (main stage), and quartz-carbonate (late stage). Gold is mainly deposited in the mainstage.

2 Fluid inclusions 2.1 Fluid inclusion types and assemblages

Three types of primary fluid inclusions were

identified by microthermometry and Raman spectroscopy, which are type 1 H2O-rich H2O-CO2-NaCl±CH4 inclusions, type 2 CO2-rich H2O-CO2±NaCl±CH4 inclusions and type 3 CO2±CH4 inclusions.

Type 1 inclusions contain an aqueous phase and one (either CO2 vapor or CO2 liquid) or two (both CO2 vapor and CO2 liquid) CO2 phases at room temperature. The volume of CO2 phase(s) accounts for 3-25% of the inclusion. These inclusions with 3-12 μm diameter have regular

to negative crystal shape and appear alone or as clusters. Type 2 inclusions, similar to type 1 inclusions, also contain two or three phases, nevertheless showing a larger CO2 phase(s) ratio of 35~70% on a volume basis. Type 3 inclusions consist of CO2 vapor and CO2 liquid, and are generally small (3-5 μm). They have regular shape and appear alone or coexist with other types of inclusions.

The early stage quartz contains just type 1 inclusions, while the main stage quartz contains a large number of type 1 inclusions, a few type 2 inclusions and rare type 3 inclusions. A combination of the type 1 and 2 primary fluid inclusions occurring together within the same growth feature in the main stage quartz, constituting a fluid inclusion assemblage.

2.2 Microthermometry and Laser Raman results

Six typical samples, two from early stage and four from main stage, were chosen for microthermometry and Laser Raman spectroscopic analysis.

For early stage, melting temperatures of the carbonic phase (TmCO2) in type 1 inclusions range between -57.5 and -56.6 C, partly below CO2 triple point (-56.6 C), suggesting that the carbonic phase contains minor quantities of volatiles. Melting temperatures of the CO2


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clathrate (Tmclath) are 6.2-9.3 °C. Homogenization of CO2 (ThCO2) occurs between 24.0 and 29.9 C. Total homogenization (ThTOT) into liquid occurs between 285 and 336 C (mean 306±13 C; 1σ; n = 32). For main stage, type 1 and 2 inclusions show similar phase-transition temperature. The TmCO2 ranges from -60.2 to -56.6C, suggesting that the carbonic phase contains a little more volatiles than those in early stage. The Tmclath is between 5.0 and 9.9 C and the ThCO2 is between 17.2 and 29.4 C. These inclusions show final homogenization to liquid or sometimes to vapor at temperatures between 212 and 314C (mean 265±25 C; 1σ; n = 121). The ThCO2 of the type 3 inclusions ranges from 23.2 to 28.8 C.

Laser Raman spectroscopy analysis for type 1 and 2 inclusions identified the CO2 phase as CO2±H2O±CH4, and no H2S or N2 were detected. And the type 3 inclusions were identified as CO2±CH4.

2.3 Composition and density of fluid inclusions

Salinities of inclusions in early and main

stage range of 1.4-7.1 and 0-9.1 eq.wt% NaCl, respectively. Type 1 inclusions in early stage consist of ca.88 mol% H2O and CO2 varying from 7 to 18 mol% with an average of 10 mol%. CO2 in type 1 and 2 inclusions of main stage range of 3-12 and 22-72 mol%, respectively. The average content of CO2 in main stage is 11mol%.

Mean bulk densities of inclusions in the two samples from early stage are 0.904 and 0.987 g/cm3, respectively, while in the four samples from main stage are 0.878, 0.910, 0.918 and 0.941 g/cm3, respectively.

3 Discussion and conclusions

Fluid inclusions in early stage show a

generally constant composition and density, indicating that the initial ore-forming fluids of Taishang deposit was H2O-CO2-NaCl homogeneous fluids. It is common that type 1 and 2 inclusions in main stage occur together within the same growth feature and have a similar total homogenization temperature. Combined with the very different XCO2 of the two type inclusions, fluid immiscibility processes operating on the originally

homogeneous single fluid could likely take place during its entrapment (Ramboz et al., 1982).

Fig. 1. Representative isochores for H2O-CO2-

NaCl±CH4 inclusions and the solvus for H2O-CO2

fluids containing 6 eq.wt% NaCl and 10 mol% CO2

(Bowers and Helgeson, 1983). Solid and dashed lines

define the range of ThTOT and bulk density of fluid

inclusions in early stage and main stage, respectively.

The dark area shows the P-T conditions of FI

entrapment of early stage. The light grey area shows

the P-T window of main stage. Fig. 1 shows representative isochores and

the solvus for H2O-CO2-NaCl fluids containing 6 eq.wt% NaCl and 10 mol% CO2. Also plotted is the homogenization temperature of early and main stage (306±13C and 265±25C). The dark shadow is over the solvus, while most of the area of light shadow is under the solvus, demonstrating that the initial homogeneous fluids gradually evolved into immiscible fluids. Thus the P-T conditions of gold mineralization range from 1580 to 720 bars and 290 to 240C.

Fluid immiscibility can be caused via fluid-pressure cycling during the evolution of the vein system caused by fault movements, as described by Wilkinson and Johnston (1996). And the fluid inclusion results suggest that similar with some of the gold deposits in Jiaodong (Yang et al., 2009; Wang et al., 2014), fluid immiscible process caused by seismic movement along fault zones that host lode gold ore bodies and subsequent lowering of the gold solubility is interpreted to be the principal precipitation mechanism of gold mineralization at the

45

Taishang gold deposit.

Acknowledgments This work was financially supported by the

National Natural Science Foundation of China (Grant No. 41230311), the National Science and Technology Support Program (Grant No. 2011BAB04B09), Geological investigation work project of China Geological Survey (Grant No. 12120114034901), and Open Research Fund Project of State Key laboratory of Geological Processes and Mineral Resources (Grant No.GPMR201307). References

Bowers, T.S., Helgeson, H.C., 1983. Calculation

of thermodynamic and geochemical consequences of nonideal mixing in the system H2O-CO2-NaCl on phase relations in geologic systems: Equation of state for H2O-CO2-NaCl fluids at high pressures and

temperatures. Geochimica et Cosmochimica Acta, 47: 1247-1275.

Ramboz, C., Pichavant, M., Weisbrod, A., 1982. Fluid immiscibility in natural processes: use and misuse of fluid inclusion data, II. Interpretation of fluid inclusion data in terms of immiscibility. Chemical Geology, 37: 29-48.

Wang, Z.L., Yang, L.Q., Guo, L.N., Marsh, E., Wang, J.P., Liu, Y., Zhang, C., Li, R.H., Zhang, L., Zheng, X.L., Zhao, H., 2014. P-T conditions and mechanisms for precipitation of gold in the Xincheng deposit, Jiaodong Peninsula, China: A fluid inclusion study. Ore Geology Reviews, submitted.

Yang, L.Q., Deng, J., Guo, C.Y., Zhang, J., Jiang, S.P., Gao, B.F., Gong, Q.J., Wang, Q.F., 2009. Ore-Forming Fluid Characteristics of the Dayingezhuang Gold Deposit, Jiaodong Gold Province, China. Resource geology, 59(2): 181-193.

2014 Convention & 11th International Conference on Gondwana to Asia


Abstract Volume


Geodynamic setting of Mesozoic gold metallogeny in the

western Shandong Province

Pu Guoa,b, Sheng-Rong Lib, M. Santoshb,c

aSchool of Resources and Materials, Northeastern University at Qinhuangdao, 143 Taishan Road,

Qinhuangdao 066004, Hebei Province, China bSchool of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road,

Beijing 100083, China cFaculty of Science, Kochi University, Kochi 780-8520, Japan

The scale and characteristics of gold metallogeny in the Luxi area along the southeastern margin of the North China Craton is in marked contrast with those in the Jiaodong area along the eastern Tan-Lu fault. This thesis summarizes the petrologic features，major and trace element geochemistry, compositions of main minerals including feldspar, biotite and hornblende, zircon U-Pb geochronology, fission track chronology and Lu-Hf isotopes of ore-bearing magmatic rocks and combines these results with salient regional geophysical data, S, Pb, H-O, C-O, He-Ar isotopes, and fluid inclusion data on ores in Luxi and Jiaodong to discuss the geodynamic setting of the gold mineralization in western Shandong Province.

Luxi and Jiaodong area have different lithospheric structures. In a detailed synthesis, this work combined the magnetotelluric data, gravity data, heat flow and other geophysical data of the profiles crossing Tan-Lu fault which reveal that the lithospheric thickness and crustal thickness of Luxi area are 64-85 km and 35-38 km respectively. The former is obviously larger than the Jiaodong region with thickness of 63-72 km, and the latter has no marked difference with Jiaodong area.

The combined Sr-Nd-Pb and Lu-Hf geochemical features of intermediate-mafic

magmatic units and their xenoliths in Shandong Province show that the mantle beneath the Luxi area is mainly of EM1 type, and the mantle in the eastern part, close to the Tan-Lu fault shows mixed EM1 and EM2 features, whereas the mantle beneath the Jiaodong area is mainly of EM2 type. The EM1 type is related to recycling ancient lithosphere mantle, whereas the EM2 type is associated with the Yangtze craton subduction.

The zircon U‒Pb data on the basement rocks in the Luxi area show that the protoliths of the TTG (tonalite-trondhjemite-granodiorite) gneisses, granitoids and amphibolites formed at 2572.2±8.8 Ma, 2531±12 Ma, and 2572±32 Ma respectively. The Mesozoic Tongshi complex in Guilaizhuang gold deposit formed at 178.4±2.1‒175.6±1.7 Ma; the diorite porphyry of Tongjing complex related to Yinan gold deposit was emplaced at 128.0±5.4 Ma. During the Mesozoic, Luxi area had two tectono-magmatism-metallogeny events: around 180 Ma and 130 Ma.

The Tongshi complex belongs to high-K alkaline and aluminum–peraluminous series, with the geochemical data displaying weakly negative europium anomalies, enrichment of large ion lithophile elements, and depletion in high field strength elements, suggesting fractional crystallization of magmas derived

47

from enriched mantle together with younger crustal components. The Tongjing complex belongs to high-K calc-alkaline and aluminum series, and lacks negative europium anomalies. The rock displays high Sr, low Y content, and Mg# value between 52.19 and 67.13 suggesting high-Mg diorite composition derived from enriched mantle. The Jinchang complex of Jinchang gold deposit belongs to I-type granite derived from the partial melting of lower crust and mixed with the mafic magma from enriched mantle.

The average zircon crystallization temperature of Tongshi complex is 672.53oC, and the oxygen fugacity is -14.8 to -11.9. The average zircon crystallization temperature of Tongjing complex is 743.68oC, and the oxygen fugacity is -12.2 to -11.7. The EPMA data of pargasite in the Tongshi complex, shows that the rim and core compositions are identical, the magma chamber depth of Tongshi complex is estimated to be between 9 and 31.6 km with mean value of 21 km, but the temperature, pressure, oxygen fugacity and H2O content in the melt of Tongjing complex shows a reduction from core to rim. The magma chamber depth of Tongjing complex is 4.8 to 21.5 km with mean value of 15 km, and its emplacement depth is between 1.9 and 16.4 km, with a mean of 8.4 km.

From Tongshi complex cooling stage to 133-140 Ma, the uplift rate is estimated as 0.34-

0.39 km/Ma; from 130 Ma to 91 Ma, its uplift rate is 1.13m/Ma; then from 90 Ma to current level, its uplift rate is 45.5-47.7 m/Ma and the mean denudation depth is 4.2 km. From Tongjing complex cooling stage to 87-100 Ma, the uplift rate is estimated as 0.33-0.51 Km/Ma; then from 87-100 Ma to current level, its uplift rate is 63.6-73.1 m/Ma and the mean denudation depth is 6.4 km. In addition, the uplift rate and depth of Luxi area is higher than that of Jiaodong.

Comparison of S, Pb, C-O, H-O, He-Ar isotope and fluid inclusion characters of ores from Luxi and Jiaodong areas, lead to the inference that the ore-forming fluid of Luxi area has a crust-mantle mixed magmatic hydrothermal signature with dominant input from mantle sources. The ore-forming materials were derived from complexes during the same period. However, the ore-forming materials in the Jiaodong area were derived from multiple sources, including the 110-130 Ma granites and intermediate-mafic dykes.

In summary, the collision between the Yangtze Craton and the North China Craton probably marks the prelude for lithosphere modification of Luxi and Jiaodong, but the different extent of modified lithospheric mantle induced by the Jurassic-Cretaceous subduction of the Pacific plate and subsequent asthenosphere upwelling is the main factor of metallogenic differences in these two areas.



Abstract Volume


Diachronous collisions across a craton-mobile belt

interface in the eastern Indian shield

Saibal Gupta

Dept. of Geology & Geophysics, IIT Kharagpur, Kharagpur – 721 302, India

In the eastern part of the Indian shield, a granulite terrane called the Eastern Ghats Belt (EGB) is considered to have been continuous with east Antarctica in the Proterozoic time. In the late Mesoproterozoic to early Neoproterozoic time (~1.0 Ga), the EGB along with east Antarctica collided with the Archaean cratons of peninsular India, viz., Dharwar, Bastar and Singhbhum, during the formation of the supercontinent Rodinia. It is widely believed that the celebrated ultrahigh temperature metamorphism of the EGB granulites overlapped with this collision event. Thus, it logically follows that the collisional interface or suture, between the EGB and the Indian cratons must also be around ~1.0 Ga old.

Interestingly, the ~1.0 Ga granulites of the Eastern Ghats Province (or EGP), are separated from amphibolite facies gneisses of the craton sensu stricto by suites of granulites that are supposed to be Archaean in age. The belt of Archaean granulites in the west, lithologically

described as the Western Charnockite Zone, is recognized as a distinct entity called the Jeypore Province. Similarly, the EGP is bordered to the north by Archaean gneisses, including granulites, of the Rengali Province. The status of these older granulites remains uncertain. It is argued that the presence of Archaean and Proterozoic granulites in juxtaposition along an ancient collisional interface may not necessarily be coincidental. The earlier granulites may represent Archaean boundaries that were simply preferentially rejuvenated in the Proterozoic as they persisted as crustal-scale weak zones. Indeed, it appears that these locales remained susceptible to reactivation even in subsequent intracontinental settings. Part of the EGB-craton interface, in fact, is seismically vulnerable even in the present day. The contact between the Eastern Ghats Belt and the craton, therefore, is the site of a diachronous collision; it is possible that this very locale may also be the site of rifting and future collisions.



Abstract Volume


Mechanisms of gold metallogeny in the North China

Craton: Insights from geophysical data

Chuansong Hea*, M. Santoshb

aInstitute of Geophysics, China Earthquake Administration 100081, Beijing, China bSchool of Earth Sciences and Resources, China University of Geosciences, 100083, Beijing, China

The North China Craton (NCC) is bounded by the early Paleozoic Qilian orogen in the west, the late Paleozoic to Mesozoic Central Asian Orogen in the north, and the Mesozoic Qinling–Dabie–Sulu orogen in the south (Zhao et al., 2001; Xu et al., 2012) and formed by the amalgamation of a number of micro-continental blocks (Zhai and Santosh, 2011). The NCC is composed of two major blocks, the Eastern Block and the Western Block which amalgamated along the Trans-North China Orogen (Zhao and Zhai, 2013) (Fig. 1). It is widely accepted that the old, thick and refractory lithospheric keel beneath the eastern NCC was replaced by young and fertile lithospheric mantle during the Mesozoic and Cenozoic (Menzies et al., 1993; Li and Santosh, 2013; Zhai and Santosh, 2013).

Recent studies report the possible existence of an upwelling or plume beneath the northern part of the Trans-North China Orogen and the eastern NCC, which resulted in magmatic underplating beneath the lower crust in this area (He et al., 2013). The westward subduction of the Pacific Plate and resultant compression led

to lower crustal and (or) lithospheric delamination in the central and southern part of the eastern NCC. Eventually, both upwelling mantle plume and lower crust and (or) lithospheric delamination resulted in lithospheric thinning and craton destruction in the eastern NCC (He et al., 2013). Here we discuss the tectonic setting of the Mesozoic gold mineralization in the NCC in the light of these new models.

Most of the previous studies on the gold mineralization in the NCC have identified a correlation between the metallogeny and lithospheric thinning in the late Mesozoic (Goldfarb and Santosh, 2014). Based on geophysical evidence, we suggest that the upwelling mantle plume might be a major factor that contributed to the lower crustal and (or) lithospheric delamination and gold mineralization (Yang and Santosh, 2014). Our studies do not support the model of stagnant slab of the Pacific plate in the mantle transition zone beneath the NCC, with upwelling connected to the gold mineralization.

References

He, C.S., Dong, S.W., Santosh, M., Li, Q.S., Chen, X.H., 2013.Destruction of the north China Craton: a perspective based on receiver function analysis. Geological Journal, DOI:

10.1002/gj.2530. Goldfarb, R.J., Santosh.,M., 2014. The dilemma of

the Jiaodong gold deposits: Are they unique? Geoscience Frontiers 5, 139-153.

50

Li, S.R., Santosh, M., 2013.Metallogeny and craton destruction: records from the North China Craton. Ore Geology Reviews, http://dx.doi.org/10.1016/j.oregeorev.2013.03.002.

Menzies, M.A., Fan, W.M., Zhang, M., 1993.Palaeozoic and Cenozoic lithoprobes and the loss of >120 km of Archaean lithosphere Sino-Korean Craton, China. Magmatic Processes and Plate Tectonics, Geological Society London 76, 71–81.

Xu, Z., Zhao, Z.F., Zheng, Y.F., 2012. Slab–mantle interaction for thinning of cratonic lithospheric mantle in North China: Geochemical evidence from Cenozoic continental basalts in central Shandong. Lithos 146-147, 202–217.

Yang, Q.Y., Santosh, M., 2014.Early Cretaceous magma flare-up and its implications on gold

mineralization in the Jiaodong Peninsula, China. Ore Geology Reviews, http://dx.doi.org/10.1016/j.oregeorev.2014.01.004.

Zhai, M.G., Santosh, M., 2011. The early Precambrian odyssey of the North China Craton: a synoptic overview. Gondwana Research 20, 6–25.

Zhai, M.G., Santosh, M., 2013.Metallogeny of the North China Craton: link with secular changes in the evolving Earth. Gondwana Research, http://dx.doi.org/10.1016/j.gr.2013.02.007.

Zhao, G.C., Wilde, S.A., Cawood, P.A., Sun, M., 2001. Archean blocks and their boundaries in the North China Craton: lithological, geochemical, structural and P–T path constraints and tectonic evolution. Precambrian Research 107, 45–73.



Abstract Volume


Basement signature of Junggar Basin: New constraints

from borehole cores and deep seismic reflection

Dengfa He*, Di Li, Delong Ma, Jieyun Tang, Zejun Yi, Yanhui Yang, Yichi Lian

The Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, the

Ministry of Education, China University of Geosciences, Beijing 100083, China

*Corresponding author Email: [email protected]

The basement nature of Junggar Basin is an important topic concerning the basin evolution and continental growth of CAOB, yet this still remains highly controversial, with views varying from the existence of Precambrian basement as its continental block to a basement of Paleozoic oceanic crust or oceanic island arc complexes. Here, we focus on the deep architecture of Junggar Basin and its nature, using deep seismic reflection together with zircon Hf isotopic analysis carried out on Late Paleozoic strata, in order to provide new constraints on the basement nature of Junggar Basin. Most Carboniferous volcanic rocks, obtained from seven wells within Junggar Basin, have positive εHf(t) values except for minor negative εHf(t) values in the western Junggar Basin, suggesting that the Junggar Basin is mainly dominated by juvenile crust without the large-scale Precambrian basement. The basement, if it exists, is limited and only located in the western part of Junggar Basin. Moreover,

the 2D seismic profile suggests that Junggar Basin has duplex basement structure according to the differences in wave velocity. The upper part is the Hercynian folded basement, whereas the lower part is the ancient crystalline basement. Furthermore, the deep seismic reflection profiles and drilling data confirm that the basement of Junggar Basin is chiefly composed of Hercynian folded basement. These Hercynian volcanic rocks have typical arc-like geochemical characteristics with low TiO2 contents, enrichment in LILEs and depletion in HFSE, suggesting that they are products of subduction-related magmatism. These results, in combination with previous data in the East and West Junggar terrane, imply that the Junggar Basin probably has a basement collage made up of Paleozoic juvenile crust and minor pre-Cambrian basement.

References

Xiao, W.J., Huang, B., Han, C., Li, J., 2010. A review of the western part of the Altaids: a key to understanding the architecture of accretionary orogens. Gondwana Research 18, 253-273.

Zhao, J.M., Huang, Y., Ma, Z.J., Shao, X.Z., Cheng, H.G., Wang, W., Xu, Q., 2008. Discussion on the basement structure and property of northern Junggar Basin. Chinese Journal of Geophysics 51, 1767-1775.



Abstract Volume


Petrology and fluid inclusions of garnet-pyroxenite from

Vadugappatti in the Palghat-Cauvery Suture Zone,

Southern India

Minako Iinuma a, Toshiaki Tsunogae b,c, M. Santosh d, T.R.K. Chetty e

aGraduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan bFaculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan cDepartment of Geology, University of Johannesburg, Auckland Park 2006, South Africa dSchool of Earth Sciences and Resources, China University of Geosciences Beijing, No. 29, Xueyuan

Road, Haidian District, Beijing 100083, China eNational Geophysical Research Institute, Uppal Road, Hyderabad 500007, Andhra Pradesh, India

The E-W trending Palghat-Cauvery Suture Zone (PCSZ) in southern India is defined as the boundary between the two contrasting tectonic provinces; the Archean terrane (e.g., Salem Block and Dharwar Craton) to the north and the Proterozoic granulite-facies blocks (e.g., Madurai and Trivandrum Blocks) to the south. The PCSZ is regarded as the zone of closure of the Mozambique Ocean in the latest Neoproterozoic related to the final stage of collision of the Gondwana supercontinent (e.g., Santosh et al., 2009, 2011). Dominant lithologies in the PCSZ are biotite-hornblende orthogneiss, charnockite, mafic-ultramafic rock, metasediments, and minor sapphirine-bearing granulites. Among these, the mafic-ultramafic rocks probably represent the remnants of both Neoarchean and Neoproterozoic suprasubduction zone ophiolites (e.g., Yellappa et al., 2011, 2014; Santosh et al., 2012, 2013; Koizumi et al., 2014). Recent petrological investigations of the mafic-ultramafic rocks in the PCSZ suggest that they preserve thermal history of the prograde stage, which possibly implies subduction of oceanic plates to lower

crustal level during or prior to the final Neoproterozoic collision. Detailed petrological investigation on mafic-ultramafic rocks within the PCSZ is therefore a key to understanding the tectonic evolution of the suture zone. In this study, we report new petrological data on mafic-ultramafic rocks from Vadugappatti in Namakkal district within the central part of the PCSZ, and discuss its petrological implications. We also performed fluid inclusion study of the rocks to infer the nature of fluid associated with the high-grade metamorphism.

Metagabbroic garnet-bearing mafic granulites (garnet pyroxenites) in Vadugappatti are exposed in the western margin of ‘Saruvamalai Hill’, extending for 13 x 2.5 km, elongated along the regional WNW-ESE foliation of the surrounding orthogneiss. Koizumi et al. (2014) obtained U-Pb zircon ages from a similar garnet pyroxenite collected from Aniyapuram locality, about 9 km west from Vadugappatti in the central part of Saruvamalai Hill, and reported Neoarchean to Early Paleoproterozoic magmatic age and Mid-Neoproterozoic (Cryogenian) metamorphic age.

53

The garnet pyroxenites in Vadugappatti are composed mainly of coarse-grained garnet, clinopyroxene, orthopyroxene, plagioclase, and quartz. Garnet occurs as subidioblastic minerals in the matrix of clinopyroxene, and is sometimes surrounded by orthopyroxene + plagioclase corona probably formed by the reaction: Grt + Qtz => Opx + Pl, suggesting decompression from prograde high-pressure stage (e.g., Saitoh et al., 2011; Koizumi et al., 2014). In contrast, garnet in the more feldspathic rocks is present as fine-grained euhedral minerals together with quartz, and such garnet + quartz aggregates surround subidioblastic clinopyroxene. The texture, which has not so far been reported from the PCSZ, suggests the progress of a reaction: Cpx + Pl => Grt + Qtz, which is probably related to post-peak cooling event. The peak metamorphic temperature was estimated by Grt-Opx geothermometers as 850-880 °C at 8 kbar, which is comparable with the results of previous studies (e.g., Koizumi et al., 2014).

Trapped fluids occur as primary inclusions in coarse-grained garnet in the garnet pyroxenite. The melting temperatures of the inclusions are close to the triple point of pure CO2 (–56.6 °C), suggesting that the trapped fluids are carbonic. Similar carbonic fluid inclusions have been reported from garnet-bearing mafic granulites from Sittampundi, Perundurai, and Kanja Malai in the PCSZ (Santosh et al., 2010). However, the timing of peak metamorphism of Sittampundi and Kanja Malai is regarded as Neoarchean (Saitoh et al., 2011; Ram Mohan et al., 2013), and that of Perundurai is unknown. As the timing of metamorphism of granulites in Saruvamalai Hill is inferred as ca. 730 Ma (Koizumi et al., 2014), this is the first report of CO2-rich fluid inclusions from the Mid-Neoproterozoic (Cryogenian) metamorphic rocks in the PCSZ. Our results suggest that CO2 is a dominant fluid component during the Neoarchean, Mid-Neoproterozoic, and Late-Neoproterozoic high-grade metamorphism within the PCSZ.

References

Koizumi, T., Tsunogae, T., Santosh, M., Tsutsumi, Y., Chetty, T.R.K., Saitoh, Y., 2014. Petrology and zircon U-Pb geochronology of metagabbros from a mafic-ultramafic suite at Aniyapuram: Neoarchean to Early Paleoproterozoic convergent margin magmatism and Middle Neoproterozoic high-grade metamorphism in southern India. Journal of Asian Earth Sciences, doi: 10.1016/j.jseaes.2014.04.013.

Ram Mohan, M., Satyanarayanan, M., Santosh, M., Sylvester, P.J., Tubrett, M., Lam, R., 2013. Neoarchean suprasubduction zone arc magmatism in southern India: Geochemistry, zircon U-Pb geochronology and Hf isotopes of the Sittampundi Anorthosite Complex. Gondwana Research 23, 539-557.

Saitoh, Y., Tsunogae, T., Santosh, M., Chetty, T.R.K., Horie, K., 2011. Neoarchean High-pressure metamorphism from the

northern margin of the Palghat-Cauvery Suture Zone, southern India: petrology and zircon SHRIMP geochronology. Journal of Asian Earth Sciences 42, 268-285.

Santosh, M., Maruyama, S., Sato, K., 2009. Anatomy of a Cambrian suture in Gondwana: Pacific-type orogeny in southern India?

Gondwana Research 16, 321-341. Santosh, M., Tsunogae, T., Shimizu, H., Dubessy,

J., 2010. Fluid characteristics of retrogressed eclogites and mafic granulites from the Cambrian Gondwana suture zone in southern India. Contributions to Mineralogy and Petrology 159, 349-369.

Santosh, M., Xiao, W.J., Tsunogae, T., Chetty, T.R.K., Yellappa, T., 2012. The Neoproterozoic subduction complex in southern India: SIMS zircon U-Pb ages and implications for Gondwana assembly. Precambrian Research 192-195, 190-208.

Santosh, M., Shaji, E., Tsunogae, T., Ram Mohan, M., Satyanarayanan, M., Horie, K., 2013. Suprasubduction zone ophiolite from Agali hill: Petrology, zircon SHRIMP U-Pb geochronology, geochemistry and implications for Neoarchean plate tectonics in southern India. Precambrian Research 231, 301-324.

Yellappa, T., Chetty, T.R.K., Tsunogae, T., Santosh, M., 2010. The Manamedu Complex: Geochemical constraints on Neoproterozoic suprasubduction zone ophiolite formation within the Gondwana suture in southern India. Journal of Geodynamics 50, 268-285.

Yellappa, T., Venkatasivappa, V., Koizumi, T., Chetty, T.R.K., Santosh, M., Tsunogae, T.,

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2014. The mafic-ultramafic complex of Aniyapuram, Cauvery Suture Zone, Southern India: Petrological and geochemical constraints for Neoarchean suprasubduction

zone tectonics. Journal of Asian Earth Sciences, doi: 10.1016/j.jseaes.2014.04.023.



Abstract Volume


Sr-Nd-Hf isotopic characterization of granitoids in

accretionary orogens of Asia and implications for crustal

development

Bor-ming Jahna*,Ying Tonga,b, Tao Wangb, Kazuaki Okamotoc, Galina Valuid and

Masako Usukia

aDepartment of Geosciences, National Taiwan University, Taipei, Taiwan 106 bInstitute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China cDepartment of Earth Science, Saitama University, Saitama 338-8570, Japan dFar Eastern Geological Institute, Russian Academy of Sciences, Vladivostok, Russia *Corresponding author e-mail: [email protected]

Asia may be broadly viewed as composed of several major Precambrian cratons (Siberia, Sino-Korean, Tarim, India) welded by Phanerozoic mobile belts or orogens. Three gigantic mobile belts are best recognized: (1) the Altaids or Central Asian Orogenic Belt (CAOB), (2) the Tethysides, and (3) the Nipponides (Sengor and Natal’in, 1996) or Western Pacific Orogenic Belt. Mobile belts were formed through successive accretion of island arc terranes and dispersed micro-continental fragments within the Paleo-Asian Ocean (for the CAOB), Paleo- and Neo-Tethys (for the Tethysides), and Paleo-Pacific and Pacific Oceans (for the Nipponides).

The Phanerozoic mobile belts comprise many accretionary orogens which have been shown to be important building blocks of the continental crust. In this talk, new and literature-based isotopic data (Sr-Nd-zircon Hf) will be used to address the issue of granitoid generation and crustal development, particularly in the CAOB and Nipponides. Extensive geochemical and isotopic studies of granitic rocks in the last decade have revealed that (a) the generation of these rocks from the CAOB involved significant

contribution from the upper mantle; that is, substantial amount of juvenile crust has been added to the Asian continent; (b) the CAOB appears to have formed by the assembly of Precambrian micro-continental fragments and Phanerozoic juvenile crust produced by both lateral accretion of arc complexes and vertical accretion of underplated material of mantle derivation (e.g., Jahn, 2004; Kovalenko et al., 2004; Wang et al., 2009).

In the Nipponides, the formation style of the Japanese islands has long been taken as a classic model of the accretionary orogeny and often serves as an example for understanding the crustal evolution of other accretionary orogens (Isozaki, 1996; Maruyama et al., 1997; Isozaki et al., 2010). Available geochemical and isotopic data on granitic rocks from SW Japan suggest that a large proportion of Mesozoic and Cenozoic granitoids possess signatures of old crustal component (Jahn, 2010). Thus, the subduction-accretion complexes in SW Japan are probably composed mostly of ‘recycled’ continental crust of Proterozoic age. By contrast, the bulk crust of the Pre-Tertiary basement rocks in NE Japan (north of the Tanakura Tectonic


56

Line) and the island of Hokkaido is quite ‘juvenile’ as shown by the available geochemical and Sr-Nd-Hf isotopic compositions of the granitoids from the two regions (Jahn et al., 2014).

New zircon dating on the granitoids from the Sikhote-Alin Range (Jahn et al., in prep.) indicates that the granitoids occurring in the coastal area (south of 45°N), in the Tauka Zone, were emplaced from ca. 90 to 56 Ma; whereas those emplaced along the Central Sikhote-Alin Fault, in the Samarka Zone, were intruded during ca. 110 to 75 Ma. The Tauka and Samarka zones are Cretaceous and Jurassic accretionary complexes, respectively. Whole-rock Sr-Nd and zircon Hf isotopic data suggest that the granitoids were derived from a mixture of juvenile and recycled source rocks in variable proportions.

A comparison between the orogens of the CAOB and Nipponides leads to the following conclusions. (1)The crustal development of NE Japan (mostly juvenile) is distinguished from that of SW Japan (juvenile+recycled); NE Japan (with Hokkaido) is quite similar to the Junggar Terrane of NW China and the Lake Zone of Mongolia (CAOB), whereas SW Japan is more comparable with the composite Tianshan orogen. (2) Accretionary orogens could be distinguished by the nature of the accreted lithological assemblages. Orogens with dominantly island arc assemblage would lead to generation of granitoids with juvenile characters, as shown by the granitoids of NE Japan (Hokkaido included), the Junggar Terrane of China (e.g., Chenand Jahn, 2004;Tang et al., 2012) and the Lake Zone of Mongolia (Kovach et al., 2011). (3) By contrast, orogens with accretionary complexes developed in a Precambrian continental margin would have granitic rocks with a more crustal signature. This is represented by SW Japan, in which the ‘recycled Precambrian crust’ component is significant in the granitoid magma generation; (4) the isotopic signature of SW Japan may support the tectonic model of Maruyama et al.(1997) and Isozaki et al. (2010) in which Proto-Japan was initially developed along the coast of SE China, and shared a similar source region (the Cathaysia) with Taiwan during the late Paleozoic to late Mesozoic. The shared source of SW Japan-Taiwan-SE China is witnessed by the Nd isotopic signatures and

inherited zircon age patterns; (5) Sr-Nd isotopic differences are observed between SW Japan, NE Japan and Sikhote-Alin, suggesting that the existing tectonic correlation schemes (e.g., Khanchuk et al., 2001) of Sikhote-Alin with the Japanese Islands should be revisited with the new age and isotopic constraints. References Chen, B., Jahn, B.M., 2004. Genesis of post-

collisional granitoids and basement nature of the Junggar Terrane, NW China: Nd-Sr isotope and trace element evidence. J.Asian Earth Sci.,23, 691-703.

Isozaki, Y., 1996. Anatomy and genesis of a subduction-related orogen: a new view of geotectonic subdivision and evolution of the Japanese Islands. The Island Arc, v. 5, 289-320.

Isozaki,Y.,Aoki,K.,Nakama,T.,Yanai,S.,2010.Newinsightinto a subduction-related orogeny: a reappraisal of the geotectonic framework and evolution of the Japanese Islands. Gondwana Research,vol.18, p.82-105.

Jahn, Bor-ming, 2004.The Central Asian Orogenic Belt and growth of the continental crust in the Phanerozoic. In: Aspects of the Tectonic Evolution of China (eds., J. Malpas, C.J.N. Fletcher, J.R. Ali, J.C. Aitchison), Geol. Soc. London. Spec. Pub. No. 226, p. 73-100.

Jahn,Bor-ming,2010.Accretionary orogen and evolution of the Japanese islands: implications from a Sr-Nd isotopic study of the Phanerozoic granitoids from Japan. American Journal of Science,v.310, 1210-1249.

Jahn, B.M., Usuki, Masako, Usuki, T., Chung, S.L., 2014. Generation of Cenozoic granitoids in Hokkaido (Japan): constraints from zircon geochronology, Sr-Nd-Hf isotopic and geochemical analyses, and implications for crustal growth. American Journal of Science, v. 314, 704-750.

Khanchuk A.I. 2001. Pre-Neogene tectonics of the Sea-of-Japan region: a view from the Russian side. Earth Sci. (Chikyu Kagaku) v. 55, 275–91

Kovach,V.P., Yarmolyuk, V.V., Kovalenko,V.I., Kozlovskii,A. M., Kotov, A.B., Terent’eva,

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L.B., 2011. Composition, sources, and growth mechanisms of continental crust in the Lake Zone of the Central Asian Caledonides: II.Geochemical and Nd isotopic data. Petrology, vol.19,p.417-444.

Kovalenko, V.I., Yarmolyuk, V.V., Kovach, V.P., Kotov, A.B., Kozakov, I.K., Sal'nikova, E.B., Larin, A.M., 2004. Isotope provinces, mechanisms of generation and sources of the continental crust in the Central Asian Mobile Belt: geological and isotopic evidence. Journal of Asian Earth Sciences, v. 23, 605–627.

Maruyama,S., Isozaki,Y., Kimura,G., Terabayashi, M., 1997. Paleogeographic Maps of the Japanese Islands: plate tectonic synthesis from750 Ma to the present. The Island Arc 6,121–142.

Sengor, A.M.C. and Natal’in, B., 1996. Turkic-type orogeny and its role in the making of the continental crust. Annual Review of Earth and Planetary Sciences, v. 24, 263-337.

Tang,G.J.,Wyman, D.A.,Wang, Q.,Li,J., Li,Z.X., Zhao,Z.H.,Sun, W.D., 2012. Asthenosphere–litho sphere interaction triggered by a slab window during ridge subduction: Trace element and Sr–Nd–Hf–Os isotopic evidence from Late Carboniferous tholeiites in the western Junggar area (NW China). Earth and Planetary Science Letters,vol.329-330,p. 84-96.

Wang, Tao, Jahn, B.M., Kovach, V.P., Tong, Y., Hong, D.W., Han, B.F., 2009. Nd-Sr isotopic mapping of the Chinese Altai and implications for continental growth in the Central Asian Orogenic Belt. Lithos, 110, 359-372.



Abstract Volume


Youngest marine fossil evidence in Tibet for

disappearance of the Tethyan Ocean

Tian Jianga,b, Xiaoqiao Wana and Jonathan C. Aitchisonb

aChina University of Geosciences, 29 Xueyuan Road, Beijing 100083, China bSchool of Geosciences, University of Sydney, Sydney, NSW 2006, Australia

The Tethyan Ocean that once covered parts of southern Tibet was eliminated when the Indian and Eurasian continents collided along the Yarlung Tsangpo suture zone. The timing of the last marine sedimentary rocks thus places a constraint on this first-order tectonic event. Although several sedimentary successions have been reported from southern Tibet their documentation is commonly incomplete or important questions remain regarding stratigraphic continuity and/or the reliability of fossil identifications.

We critically assess existing data in order to correlate and compare between sections in three zones: one to the north of the suture on the Asian margin and two to the south on the northern margin of India. We examine the planktonic foraminiferal biostratigraphy of the youngest sections, which occur in the Tibetan Himalayan succession and lie around 100 km south of the suture. This also includes a previously

unreported section 70 km east of Gamba. We consider the implications of our results for understanding the timing of continent-continent collision. In doing this we take into account the effects of crustal loading, eustatic sea level variation, orogenesis associated with the on-going convergence between India and Asia at around 95 km/my, together with the likely rate migration of any fore-deep in front of a colliding continental mass.

Our foraminiferal results, together with those for other microfossil groups such as marine ostracods, nanofossils and radiolarians demonstrate that a marine seaway remained in existence south of the Yarlung Tsangpo suture zone until at least Priabonian (38-33 Ma) time. Importantly, as all sections are truncated by erosion or faulting we note that this remains a maximum estimate for the age of the last marine sedimentation in this area



Abstract Volume


Revisiting ultrahigh temperature crustal metamorphism

at regional scale – causes, tectonic setting, phase

equilibria and trace element thermometry constraints

Dave E. Kelsey* and Martin Hand

Geology and Geophysics, The University of Adelaide, South Australia 5005, Australia *Corresponding author e-mail: [email protected]

Ultrahigh temperature (UHT) crustal

metamorphism is the most thermally extreme type of crustal metamorphism, involving non-igneous crustal temperatures above 900 °C. The recent progress in understanding UHT metamorphism has led to numerous advances that have improved our understanding of thermally extreme deep crustal processes. The advances, covered in our presentation, include: 1) expanded thermodynamic models for UHT minerals such as sapphirine; 2) new chemical tools for micro-analytically quantifying metamorphic/growth temperatures such as element abundance of Zr and/or Ti in minerals; 3) a more realistic consideration of the thermal properties of the crust in geodynamic modelling, and the role this plays in the thermal structure/profile of the crust; 4) geodynamic modelling that has specifically targeted the question of how the crust attains temperatures >900 °C and what tectonic settings are most probable for generating UHT conditions; and 5) voluminous geochronological datasets that have provided much-needed information about timescales of UHT (and granulite) metamorphism. In addition, there is an increased global interest in UHT metamorphism, as shown by the greater-than-threefold (>300 %) increase in the number of scientific papers

published on or around the topic of UHT metamorphism since 2007 compared with the interval 2000–2006.

Trace element thermometry, Zr-in-rutile in particular, will lead to a significant increase in the recognition of UHT crustal metamorphism globally as the reliance on the presence of diagnostic mineral assemblages no longer applies. This represents a huge and exciting shift in focus on recognising UHT metamorphism which has traditionally relied on identifying diagnostic minerals in rare Mg-Al-rich rock compositions. Since rutile is an integral part of a mineral assemblage, is usually much coarser-grained than zircon (allowing many analyses), can be analysed for Zr using an electron microprobe and is easily included in petrologic forward modelling (pseudosections), Zr-in-rutile thermometry is greatly preferred over Ti-in-zircon thermometry.

Choosing an appropriate bulk composition is at the heart of modern day metamorphic geology as pseudosections cannot be calculated without a bulk composition. Yet, for such an extremely important aspect of metamorphic geology, our documentation is the first time that we know of where all the factors and approaches influencing the bulk composition (local or macroscopic scale) is set out and appraised. With


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regard to UHT metamorphism, the question of how to choose a bulk composition is highly relevant since UHT rocks typically contain very local-scale reaction microstructures. A brief overview of this will be given in our presentation.

In addition to trace element thermometry and bulk compositions, our presentation addresses the topic of tectonic setting for UHT metamorphism in a much more comprehensive manner than was presented in existing overviews of UHT metamorphism. Proposed sites of UHT metamorphism are mostly related to subduction processes. We also discuss the importance of the thermal properties of rocks and pre-conditioning

of rocks in the generation of sustained, regional UHT metamorphism.

These facets have become increasingly recognised (since about 2008) as important in order for the crust to reach and sustain UHT conditions for prolonged periods of time. The past 6–8 years or so has involved revisiting decades-old ideas on what causes extreme thermal metamorphism on a regional scale, in terms of rock properties as well as tectonic settings. It is interesting that some early work on high-grade gneiss terrains is only now being given the due credit it deserves.



Abstract Volume


Tectonic implication of the Paleozoic sequences, South

Korea from detrital and overgrowth zircon U‐Pb

geochronology

Sung Won Kima,*, Sanghoon Kwonb, M. Santoshc, In-Chang Ryud

aKorea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Republic of Korea bDepartment of Earth System Sciences, Yonsei University, Seoul 120-749, Republic of Korea cSchool of Earth Sciences and Resources, China University of Geosciences, Beijing, 29 Xueyuan Road,

Beijing 100083, China dDepartment of Geology, Kyungpook National University, Daegu 702-701, Republic of Korea

The Middle Paleozoic metasedimentary sequences (viz. Taean Formation and Wolhyeonri Complex) of western Gyeonggi Massif, the Imjingang Belt, and the southwestern Okcheon Belt, provide clues to the successive tectonic events during the evolution of the Korean Peninsula (Cho, 2007; Cho et al., 2010; Kwon el al, 2009; Sajeev et al., 2010; Kwon et al., 2013; Park et al., 2014). From these sequences, we have conducted SHRIMP U–Pb analyses of detrital zircons, where the results show similar U-Pb age spectra of Paleoarchean/Neoarchean to Middle Paleozoic. The dominant SHRIMP U–Pb dates are concentrated within the Paleozoic. The maximum depositional ages, based on the youngest dominant concordant detrital zircons, are estimated to be 431457 Ma from the

western Gyeonggi Massif and the Imjingang Belt, and 380355 Ma from the southwestern Okcheon Belt. Permian metamorphic zircon overgrowths are also found, correlating with subduction prior to the Triassic collision. Middle Paleozoic metamorphic zircon overgrowths are found in the Wolhyeonri Complex. Dominant zircon populations from the Korean Peninsula indicate that the sedimentary sequences were sourced from similar peripheral clastic provenance, and can be compared with those from the Yangtze, Cathaysia and Qilian–Qinling Orogenic Belt (e.g., Wan et al., 2007, 2010; Yu et al., 2008, 2010; Z.-X. Li et al., 2010; Li et al., 2012; Wang et al., 2010; Xiang and Shu, 2010; Yao et al., 2011, 2012) that are located in the northeastern margin of the eastern Gondwana assembly during Early Paleozoic.

References

Cho, D.L., 2007. SHRIMP zircon dating of a low-grade meta-sandstone from the Taean formation: provenance and its tectonic implications. Korea Institute of Geoscience and Mineral Resources Bulletin 11, 3–14.

Cho, M., Na, J., Yi, K., 2010. SHRIMP U-Pb ages of detrital zircons in metasandstones of the Taean Formation, western Gyeonggi massif, Korea: Tectonic implications. Geosciences Journal 14, 99–109.

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Kwon, S., Kim, S.W., Santosh, M., 2013. Multiple generations of mafic-ultramafic rocks from the Hongseong suture zone, western South Korea: Implications for the geodynamic evolution of NE Asia. Lithos 160–161, 68–83.

Kwon, S., Sajeev, K., Mitra, G., Park, Y., Kim, S.W., Ryu, I.-C., 2009, Evidence for Permo-Triassic collision in Far East Asia: The Korean collisional orogen. Earth and Planetary Science Letters 279, 340-349.

Li, X.-H., Li, Z.X., He, B., Li, W.-X., Li, Q.-L., Gao, Y., Wang, X.-C., 2012. The Early Permian active continental margin and crustal growth of the Cathaysia Block: In situ U–Pb, Lu–Hf and O isotope analyses of detrital zircons. Chemical Geology 328, 195–207.

Li, Z.-X., Li, X.-H., Wartho, J.-A., Clark, C., Li, W.-X., Zhang, C.-L., Bao, C., 2010. Magmatic and metamorphic events during the early Paleozoic Wuyi-Yunkai orogeny, southeastern South China: New age constraints and pressure-temperature conditions. Geological Society of America Bulletin 122, 772-793.

Park, S.-I., Kim, S.W., Kwon, S., Thanh, N.X., Yi, K., Santosh, M., 2014. Paleozoic tectonics of the southwestern Gyeonggi massif, South Korea: Insight from geochemistry, chromian-spinel chemistry and SHRIMP U-Pb geochronology. Gondwana Research http://dx.doi.org/10.1016/j.gr.2013.07.015.

Sajeev, K., Jeong, J., Kwon, S., See, W.-S., Kim, S.W., Komiya, T., Itaya, T., Jung, H.-S., Park, Y., 2010. High P–T granulite relicts from the Imjingang Belt, South Korea: tectonic significance. Gondwana Research 17, 75–86.

Wan, Y.S., Liu, D.Y., Wilde, S.A., Cao, J., Chen, B., Dong, C., Song, B., Du, L., 2010. Evolution of the Yunkai Terrane, South China: Evidence from SHRIMP zircon U–Pb dating, geochemistry and Nd isotope. Journal of Asian Earth Sciences 37, 140–153.

Wan, Y.S., Liu, D.Y., Xu, M.H., Zhuang, J.M., Song, B., Shi, Y.R., Du, L.L., 2007.

SHRIMP U–Pb zircon geochronology and geochemistry of metavolcanic and metasedimentary rocks in Northwestern Fujian, Cathaysia Block, China: tectonic implications and the need to redefine lithostratigraphic units. Gondwana Research 12, 166–183.

Wang, Y., Zhang, F., Fan, W., Zhang, G., Chen, S., Cawood, P.A., Zhang, A., 2010. Tectonic setting of the South China Block in the early Paleozoic: Resolving intracontinental and ocean closure models from detrital zircon U-Pb geochronology. Tectonics 29, TC6020, http://dx.doi.org/10.1029/2010TC002750.

Xiang, L., Shu, L.S., 2010. Pre-Devonian tectonic evolution of the eastern South China Block: geochronological evidence from detrital zircons. Science in China (D) 53, 1427–1444.

Yao, J., Shu, L., Santosh, M., 2011. Detrital zircon U–Pb geochronology, Hf-isotopes and geochemistry—New clues for the Precambrian crustal evolution of Cathaysia Block, South China. Gondwana Research 20, 553–567.

Yao, J., Shu, L., Santosh, M., Li, J., 2012. Precambrian crustal evolution of the South China Block and its relation to supercontinent history: Constraints from U–Pb ages, Lu–Hf isotopes and REE geochemistry of zircons from sandstones and granodiorite. Precambrian Research 208–211, 19–48.

Yu, J.H., O'Reilly, S.Y., Wang, L.J., Griffin, W.L., Zhang, M., Wang, R.C., Jiang, S.Y., Shu, L.S., 2008. Where was South China in the Rodinia supercontinent? Evidence from U–Pb geochronology and Hf isotopes of detrital zircons. Precambrian Research 164, 1–15.

Yu, J.H., O’Reilly, S.Y., Wang, L.J., Griffin, W.L., Zhou, M.F., Zhang, M., Shu, L.S., 2010. Components and episodic growth of Precambrian crust in the Cathaysia Block South China: evidence from U–Pb ages and Hf isotopes of zircons in Neoproterozoic sediments. Precambrian Research 181, 97–114.

http://dx.doi.org/10.1016/j.gr.2013.07.015

http://dx.doi.org/10.1029/2010TC002750



Abstract Volume


Allanite compositions of alkaline magmatic suite from

the southern periphery of the Dharwar Craton, southern

India: implications for magma mixing processes

Airi Kobayashi a, Toshiaki Tsunogae b, c, M. Santosh d

aCollege of Geosciences, University of Tsukuba, Ibaraki 305-8572, Japan bFaculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan cDepartment of Geology, University of Johannesburg, Auckland Park 2006, South Africa dJournal Centre, China University of Geosciences Beijing, No. 29, Xueyuan Road, Haidian District,


Allanite (A2M3Si3O12[OH]), a member of the epidote group, is known as an accessory mineral that can incorporate significant amounts of rare earth elements (REEs). It has been reported from various lithologies including alkaline and subalkaline granite, felsic volcanics, high-pressure metamorphic rocks, and skarns. In this study we report the occurrence of allanite in alkaline magmatic suite (Angadimogar suite; Santosh et al., 2014) from the Mercara Suture Zone, Southern India, and discuss its compositional characters that suggest magma mixing process in the alkaline rocks. The Mercara Suture Zone is regarded as a paleo-suture zone that marks the boundary between the Archean Dharwar Craton to the north and the Coorg Block, which corresponds to a Mesoarchean (~3.4 Ga) exotic continent (Santosh et al., 2013), to the south. Several Mid-Neoproterozoic alkaline magmatic suites are distributed along the southern periphery of the Dharwar Craton within the Mercara and Moyar Suture Zones.

Samples examined in this study were collected from an active quarry at Bathur in northern Kerala, where dark-colored mafic microgranular enclaves (MMEs) are distributed

within massive granite, which suggests bimodal magmatism in this region. The mineralogy of the MME, which is compositionally classified as syeno-diorite, is hornblende, clinopyroxene, epidote, biotite, titanite, and plagioclase, while the host granite contains quartz, plagioclase, K-feldspar, and biotite. Plagioclase in the contact zone between the MME and host granite shows oscillatory and dusty zonings, which are regarded as typical characters of magma mixing processes (e.g., Perugini et al., 2003).

Allanite is pleochroic (dark to light brownish), medium grained (0.5-0.9 mm), euhedral in shape, and present only along the lithological boundary between the MME and host granite. It is characterized by high REE contents of ~67,000 ppm La, ~105,000 ppm Ce, ~85,000 ppm Pr, and ~29,000 ppm Nd. Allanite is compositionally nearly homogeneous, although its TiO2 content slightly increases from core (1.4-1.5 wt.%) to rim (1.7-1.8 wt.%). Normalized REE patterns show strong fractionation of heavy over light REE, with LaN/NdN ratios between 3.9 and 5.7, which is a common feature of Ce-allanite in alkaline granites (e.g., Vlach and Gualda, 2007). The occurrence of allanite is probably related to high

64

REE contents of the MME (ΣREE = 392 ppm), which is even higher than that of the host granite (ΣREE = 122 ppm). Titanite is the only REE-bearing phase in the MME, and it contains ~2,300 ppm La, ~10,000 ppm Ce, ~3,500 ppm Pr, and ~11,000 ppm Nd. The formation of allanite might be related to magma mixing process, which could have decomposed titanite and crystallized allanite along the MME-granite boundary. Hoshino et al. (2006) argued that

high-Mn allanite (Mn > 0.14 pfu) could have formed by convergent margin tectonics possibly related to crystallization from volatile-rich magma. Low Mn content of the studied allanite (Mn < 0.14 pfu) is consistent with the proposed petrogenesis of alkaline rocks in the Angadimogar suite formed by bimodal magmatism in Mid-Neoproterozoic divergent margin in southern India (Santosh et al., 2014).

References

Hoshino, H., Kimata, M., Shimizu, M., Nishida, N., Fujiwara, T., 2006. Allanite-(Ce) in granitic rocks from Japan: genetic implications of patterns of REE and Mn enrichment. Canadian Mineralogist 44, 45-62.

Perugini, D., Poli, G., Christofides, G., Eleftheriadis, G., 2003. Magma mixing in the Sithonia Plutonic Complex, Greece: evidence from mafic microgranular enclaves. Mineralogy and Petrology 78, 173-200.

Santosh, M., Yang, Q.Y., Shaji, E., Tsunogae, T., Ram Mohan, M., Satyanarayanan, M., 2013. An exotic Mesoarchean microcontinent: The

Coorg Block, southern India. Gondwana Research doi: 10.1016/j.gr.2013.10.005.

Santosh, M., Yang, Q.Y., Ram Mohan, M., Tsunogae, T., Shaji, E., Satyanarayanan, M., 2014. Cryogenian alkaline magmatism in the

Southern Granulite Terrane, India: constraints from petrology, geochemistry, and zircon U-Pb and Lu-Hf isotopes. Lithos (under revision).

Vlach, S.R.F., Gualda. G.A.R., 2007. Allanite and chevkinite in A-type granites and syenites of the Graciosa Province, southern Brazil. Lithos 97, 98-121.



Abstract Volume


Permian age of HTLP metamorphism in the Garm block,

Tajikistan

D. Konopelkoa, R. Klemdb, Y. Mamadjanovc, D. Fidaevd, S. Sergeeva

aGeological Faculty, St. Petersburg State University, 7/9 University Embankment, St. Petersburg, 199034,

Russia bGeo Zentrum Nordbayern, Universitaet Erlangen-Nuernberg, Schlossgarten 5a, 91054 Erlangen,

Germany cInstitute of Geology, Earthquake Engineering and Seismology of the Academy Science of the Republic

of Tajikistan, 267 Ainy St. Dushanbe, 734063, Tajikistan dThe Atlantic Branch of the P.P. Shirshov Institute of Oceanology, 1 Prospect Mira, Kaliningrad, 236022,

Russia

Caledonian and Hercynian orogenic belts outcropping in the terranes of Tien Shan and Kazakhstan generally lack HTLP metamorphic belts characteristic of collisional orogens. In order to explain this feature various authors emphasized the accretionary character of these orogens (e.g. Sengor et al., 1993) which formed as a result of oblique collision with the southern Karakum-Tarim continents (Chen et al., 1999). However during the last decade mid-Paleozoic Silurian-Devonian HTLP metamorphic belts have been recognized in the Altai, Northern Tarim margin and Southern Tien Shan (Jiang et al., 2010, Mirkamalov et al., 2012, Zong et al., 2013). In this contribution we present SHRIMP data on the Garm metamorphic block in the Southern Tien Shan of Tajikistan. The Garm block is lens shaped and about 150 by 40 km in size elongated from west to east in accordance with surrounding structures of the Southern Tien Shan. The structures of the different rock types of the Garm block have a well pronounced southern vergency. Thick piles of greenschist-facies Lower Paleozoic rocks were thrust over the Garm block from north to south. The

southern margin of the Garm block is covered by the sediments of Kyzylsu river south of which the Pamirs ranges represent completely different geological structures. The rocks in the Garm block comprise upper amphibolite-facies schists, ortho- and paragneisses, amphibolites and migmatites. The metamorphic rocks are cut by numerous intrusions varying in composition from S-type to I-type granites and nepheline syenites. In the course of the present study zircon grains separated from 10 samples were dated with the SHRIMP-II (CIR VSEGEI, St. Petersburg). The investigated samples include leucosomes of migmatites, ortho- and paragneisses, ortho- and para-amphibolites as well as crosscutting granites. The results show that an HTLP metamorphic event in the Garm block occurred at ca. 290 Ma as displayed by U-Pb zircon ages of migmatitic leucosomes and crosscutting granites. The zircon core ages and one detrital zircon age from para-amphibolite reveal that the protoliths of some metamorphic rocks of the Garm block comprised Lower Paleozoic sedimentary and volcanic rocks.

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Acknowledgement This study is a contribution to IGCP

Project592 funded by IUGS and UNESCO.

References

Chen, C., Lu, H., Jia, D., Cai, D., Wu, S., 1999. Closing history of the southern Tianshan oceanic basin, western China: an oblique collisional orogeny. Tectonophysics 302, 23–40.

Jiang, Y.D., Sun, M., Zhao, G.C., Yuan, C., Xiao, W.J., Xia, X.P., Long, X.P., Wu, F.Y., 2010. The ~390 Ma high-T metamorphic event in the Chinese Altai: a consequence of ridge-subduction? American Journal of Sciences 310, 1421–1452.

Mirkamalov, R.H., Chirikin, V.V., Khan, R.S., Kharin, V.G., Sergeev, S.A., 2012. Results of U-Pb (SHRIMP) dating of

granitoid and metamorphic complexes of the Tien Shan fold belt (Uzbekistan). Vestnik SPbGU Vol. 7-1, 3-25. (In Russian).

Sengor, A.M.C., Natal'in, B.A., Burtman, V.S., 1993. Evolution of the Altaid tectonic collage and Paleozoic crustal growth in Eurasia. Nature 364, 299–307.

Zong, K., Liua, Y., Zhang, Z., Heb, Z., Hua, Z., Guoa, J., Chen, K., 2013. The generation and evolution of Archean continental crust in the Dunhuang block, northeastern Tarim craton,

northwestern China. Precambrian Research 235, 251– 263.



Abstract Volume


Palaeoproterozoic ancestry of Pan-African granitoid

rocks in southernmost India: Implications for Gondwana

reconstructions

A. Krönera,b*, M. Santoshc, E. Hegnerd, E. Shajie, H. Gengf, J. Wongf, H. Xiea, Y.

Wana, C.K. Shangd, D. Liua, M. Sunf, V. Nanda-Kumarg

aBeijing SHRIMP Centre, Chinese Academy of Geological Sciences, a,fBaiwanzhuang Road, 100037 Beijing, China; e-mail: [email protected] bDepartment of Geosciences, University of Mainz, D-55099 Mainz, Germany cJournal Center, China University of Geosciences Beijing, 29 Xueyuan Road, 100083 Beijing, China dDepartment of Geo- and Environmental Sciences and GeoBio Center,

University of Munich, D-80333 Munich, Germany eDepartment of Geology, University of Kerala, Kariavattom, Trivandrum - 695 581, India fDepartment of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China gNational Center for Earth Science Studies, Akkulam, Trivandrum 695 031, India

SHRIMP dating of magmatic zircons from granitoid gneisses (leptynites) and charnockites of the Trivandrum and Nagercoil Blocks in the granulite terrane of southernmost India yielded well-defined protolith emplacement ages between 1765 and ca. 2100 Ma and also document variable recrystallization and/or lead-loss during the late Neoproterozoic Pan-African event at around 540 Ma. Hf-in-zircon and whole rock Nd isotopic data suggest that the granitoid host rocks were derived from mixed crustal sources, and Hf-Nd model ages vary between 2.2 and 2.8 Ga. A gabbroic dyke, emplaced into a charnockite protolith and deformed together with it, only contained metamorphic zircon whose mean age of 542.3±4.0 Ma reflects the peak of granulite-facies metamorphism during the Pan-African high-grade event. The Sm-Nd whole-rock isotopic system of several granitoid samples dated in this study was significantly disturbed during granulite-facies metamorphism,

most likely due to a CO2-rich fluid phase. Whole-rock Nd model ages are consistently older than zircon-derived Hf model ages.

The Trivandrum and Nagercoil Blocks constitute a tectono-metamorphic terrane predominantly consisting of Palaeoproterozoic granitoid plutons including enclaves of supracrustal rocks largely consisting of metapelites (khondalites) that must be older than ca. 2100 Ma. Ductile deformation, migmatization and anatexis have obliterated the original rock relationships. These blocks probably have their counterpart in the Highland Complex of neighbouring Sri Lanka and in the high-grade Palaeoproterozoic terrane of southern Madagascar. We speculate that the southern Indian khondalites have similar ages as those in the North China craton, inviting speculations on a possible connection in the Palaeoproterozoic.

Convention &11th International Conference on Gondwana to Asia


Abstract Volume


Neoproterozoic and middle Phanerozoic evidence of

convergent orogenesis from the Imjingang-Hongseong

areas, Western Gyeonggi massif, South Korea

Sanghoon Kwona, *, Sung Won Kimb, M. Santoshc

aDepartment of Earth System Sciences, Yonsei University, Seoul 120-749, Republic of Korea bKorea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Republic of Korea cSchool of Earth Sciences and Resources, China University of Geosciences, Beijing, 29 Xueyuan Road,


The Imjingang-Hongseong areas of the western Gyeonggi massif, South Korea preserved signatures of convergent orogenesis during Neoproterozoic and from Paleozoic to Early Mesozoic (e.g. Ree et al., 1996; Guo et al., 2004; Oh et al., 2005; Seo et al., 2005; Cho et al., 2007; Kim et al., 2008; Kwon et al., 2009; Sajeev et al., 2010; Kim et al., 2011a, b, 2013; Park et al., 2014). Neoproterozoic records of subduction and continental rifting are preserved at both Hongseong and Imjingang areas. They are represented by arc magmas of calc-alkaline series and rift-related crustal mafic and ultramafic rocks that are derived from the amalgamation and disruption of the Rodinia supercontinent (Lee et al., 2003; Kim et al., 2013; Kwon et al. 2013). The Paleozoic evidences are better preserved in the Hongseong area, including Paleozoic hydrated forearc mantle peridotite (serpentinite) bodies enclosing high-pressure mafic and felsic blocks and Wolhyeonri forearc complex, which preserved Paleozoic high-grade metamorphism (Oh et al., 2005; Seo et al., 2005; Kim et al., 2006; Kwon et al., 2009; Kim et al., 2011 a, b; Park et al., 2014). This interpretation is evidenced by geochemistry, mineral chemistry, metamorphic petrology, primary igneous chromian spinel composition and geochronology, suggesting the existence of a mantle wedge above a ‘Pacific-type’

subduction zone during Paleozoic prior to the Early Mesozoic collision. The serpentinite bodies are interpreted as the products of significant interaction between residual mantle and melt during forearc opening and subsequent forearc evolution based on mineral chemistry and primary igneous chromian spinel compositions from the serpentinite bodies (Park et al., 2014). Thus, the Paleozoic Imjingang-Hongseong Suture Zone area might be located in a forearc setting of the suprasubduction zone environment coeval with volcanism and magmatism preserved in the Wolhyeonri complex (Park et al., 2014). The final Mesozoic collision resulted in the formation of high-pressure granulite to eclogite facies metamorphism that is preserved in the Bibong eclogite body (Guo et al., 2004; Oh et al., 2005; Kim et al., 2006), the mafic exotic blocks captured in serpentinite bodies (Kwon et al., 2009; Park et al., 2014) and the scattered diabase sills/dikes within the forearc sediments (Kwon et al., 2013) in the Hongseong area. Triassic Barrovian-type metamorphic sequences and high-grade mafic granulite facies are also reported from the Imjingang area (Ree et al., 1996; Cho et al., 2007). Both Neoproterozoic and Paleozoic to Early Mesozoic evidences from the Hongseong-Imjingang area of the western Gyeonggi massif indicate strong tectonic

69

correspondence with the Sulu belt, where the basement is known to be part of the South China Craton. The existence of anorogenic granitoids (ca. 233–226 Ma) which formed in a post-collisional tectonic setting (e.g. Seo et al., 2010; Kim et al., 2011c) further supports the Late Permian to Early Triassic collision (ca. 260–230

Ma). In summary, the Hongseong-Imjingang areas of the western Gyeonggi massif preserve important clues to the Neoproterozoic and long-lived Paleozoic to Early Mesozoic tectonic histories related to global events that were prevalent in Northeast Asia.

References

Cho, M., Kim, Y., Ahn, J., 2007. Metamorphic evolution of the Imjingang Belt, Korea: Implications for Permo-Triassic collisional orogeny. International Geology Review 49, 30–51.

Guo, J., Zhai, M., Oh, C.W., Kim, S.W., 2004. 230Ma Eclogite from Bibong, Hongseong area, Gyeonggi Massif, South Korea: HP

metamorphism, zircon SHRIMP U-Pb ages, and tectonic implication. Abstract volume of International Association for Gondwana Research, South Korea Chapter, Misc Publication, Chonju, pp.11–12.

Kim, S.W., Kee, W.-S., Lee S.R., Santosh, M., Kwon, S., 2013. Neoproterozoic plutonic rocks from the western Gyeonggi massif, South Korea: Implications for the amalgamation and break-up of the Rodinia supercontinent. Precambrian Research 227, 349–367.

Kim, S.W., Kwon, S., Koh, H.J., Yi, K., Jeong, Y., Santosh, M., 2011c. Geotectonic framework of Permo-Triassic magmatism within the Korean Peninsula. Gondwana Research 20, 865–889.

Kim, S.W., Kwon, S., Santosh, M., Williams, I.S., Yi, K., 2011b. A Paleozoic subduction complex in Korea: SHRIMP zircon U-Pb ages and tectonic implications. Gondwana Research 20, 890–903.

Kim, S.W., Oh, C.W., Williams, I.S., Rubbato, D., Ryu, I.-C., Rajesh, V.J., Kim, C.-B., Guo, J., Zhai, M., 2006. Phanerozoic high-pressure eclogite and intermediate-pressure granulite facies metamorphism in the Gyeonggi Block, South Korea: implications for the eastward extension of the Dabie-Sulu continental collision zone. Lithos 92, 357–377.

Kim, S.W., Santosh, M., Park, N., Kwon, S., 2011a. Forearc serpentinite mélange from the Hongseong suture, South Korea. Gondwana Res. 20, 852-864.

Kim, S.W., Williams, I.S., Kwon, S., Oh, C.W.,

2008. SHRIMP zircon geochronology and geochemical characteristics of metaplutonic rocks from the south-western Gyeonggi Block, Korea: implications for Paleoproterozoic to Mesozoic tectonic links between the Korean Peninsula and eastern China. Precambrian Research 162, 475–497.

Kwon, S., Kim, S.W., Santosh, M., 2013. Multiple

generations of mafic-ultramafic rocks from the Hongseong suture zone, western South Korea: Implications for the geodynamic evolution of NE Asia. Lithos 160–161, 68–83.

Kwon, S., Sajeev, K., Mitra, G., Park, Y., Kim, S.W., Ryu, I.-C., 2009. Evidence for Permo-Triassic collision in Far East Asia: The Korean collisional orogen. Earth and Planetary Science Letters 279, 340–349.

Lee, S.-R., Cho, M., Cheong, C.-S., Kim, H., Wingate, M.T.D., 2003. Age, geochemistry, and tectonic significance of Neoproterozoic alkaline granitoids in the northwestern margin of the Gyeonggi massif, South Korea. Precambrian Research 122, 297–310

Oh, C.W., Kim, S.W., Choi, S.G., Zhai, M., Guo, J., Sajeev, K., 2005. First finding of Eclogite Facies metamorphic event in South Korea and its correlation with the Dabie-Sulu Collision Belt in China. Journal of Geology 113, 226–232.

Park, S.-I., Kim, S.W., Kwon, S., Thanh, N.X., Yi, K., Santosh, M., 2014. Paleozoic tectonics of the southwestern Gyeonggi massif, South Korea: Insight from geochemistry, chromian-spinel chemistry and SHRIMP U-Pb geochronology. Gondwana Research

http://dx.doi.org/10.1016/j.gr.2013.07.015.

http://dx.doi.org/10.1016/j.gr.2013.07.015

Convention &11th International Conference on Gondwana to Asia


Abstract Volume


A massif-type (~1.86 Ga) anorthosite complex in the

Yeongnam Massif, Korea: Late-orogenic emplacement

associated with the mantle delamination in the north

China Craton

Yuyoung Leea,*, Moonsup Choa, Wonseok Cheonga, Keewook Yib

aSchool of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, South Korea, bKorea Basic Science Institute, Ochang, Chungbuk, 363-833, South Korea

*Corresponding author e-mail: [email protected]

In order to unravel the petrogenesis of the massif-type anorthosite in light of the crust-mantle geodynamics, we dated zircons separated from three anorthositic rocks and three gneisses of the Sancheong-Hadong (SH) complex, Korea, using a sensitive high-resolution ion microprobe. The weighted mean 207Pb/206Pb age of two anorthosites is 1862±2 Ma, whereas the ages of hornblende gabbro and granitic gneiss are 1873±4 Ma and 1875±5 Ma, respectively. In contrast, zircon rims from mafic granulite and migmatitic gneiss are dated at 1860±5 Ma and

1858±4 Ma, respectively, suggesting that the granulite-facies metamorphism and anatexis are associated with anorthosite emplacement. Our result together with the available Re-Os data is compatible with the ~1.9–1.87 Ga collisional orogeny which has not only been documented throughout the North China Craton, including the Korean Peninsula, but also accompanied by the mantle delamination beneath the craton. It is thus likely that the SH anorthosite is a product of late-orogenic magmatism.



Abstract Volume


Late ontogeny of the trilobite Tsinania shanxiensis

(Zhang et Wang, 1985) from the Cambrian (Furongian)

of Anhui, China and its systematic implications

Qian-Ping Leia, b,*, Qing Liub

aNatural Department, Changzhou Museum, Changzhou, China bState Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and

Palaeontology, Nanjing, China

The ontogenetic study of trilobites is generally regarded as informative and useful for dealing with the higher-level classification of trilobites. It has been widely used in trilobite taxonomy and is also expected to play a vital role in elucidating Cambrian trilobite phylogeny. In spite of the late holaspid pygidium resembling certain Asaphoidea, Shergold (1975) first proposed that the family Tsinaniidae should be classified within the Superfamily Leistegioidea on the basis of their morphogenetic similarities. However, it was again suggested to be a member of the order Asaphida owing to its close morphological similarity to Asaphidae when describing a new species of Shergoldia. Recently, the postembryonic development of Tsinania canens from Korea revealed that this trilobite had an adult-like protaspis, and Park et al. (2013) further report four species of Mansuyia as the stem-group taxa to the family Tsinaniidae. With the new study on Lonchopygella megaspina by Zhu et al. (2013), there seems no doubt that Tsinaniidae is likely to be closely related to the leiostegioids. Moreover, Park et al. (2013) proposed the generic and familial boundary situated between Mansuyia taianfuensis and Shergoldia laevigata.

The genus Guluheia was first established by

Zhang and Wang in 1985, and its type species is Guluheia shanxiensis found in Shanxi, China. It is naturally placed in the Family Tsinaniidae owing to its adult morphology, whereas it shares some similarities on the cranidium and pygidium with the kaolishaniids. Its generic diagnosis is based on exfoliated specimens that are generally similar to that of Tsinania except for bearing a pair of short spines on the pygidium. However, based on our specimens, the validity of this genus should be reconsidered.

A new occurrence of Tsinania shanxiensis (Zhang and Wang, 1985) comb. nov., is reported herein from northern Anhui, China. This species has been here transferred from Guluheia to Tsinania as the differences between the two genera are not enough to support intergeneric variation. The late ontogeny of T. shanxiensis has been studied herein and possibly serves as another important proof for the systematic position of the Family Tsinaniidae. The ontogeny of the Furongian trilobite Tsinania shanxiensis, reveals that it has a dramatic change in the pygidium during its ontogenetic development: the long anterior pleural spines rapidly decrease to a pair of small tubes. Based on the new material, the late ontogeny of the pygidia of T. shanxiensis is divided into four

72

stages: (the pygidial spine-bearing segment) PSS+2 stage, PSS+1 stage, early holaspid stage and late holaspid stage. In the light of the immature morphology of T. shanxiensis retaining long pygidial spines which is very similar to some species of Mansuyia and having

residual short spines on the holaspis, it can be regarded as the transitional type between some latest species of Mansuyia (e.g., Mansuyia orientalis, M. tani) proposed by Park et al. (2013) and the more evolved species of Tsinania (e.g., T. canens) during the middle Furongian.



Abstract Volume


Late Paleozoic tectono-depositional evolution of Junggar

Basin

Di Li*, Dengfa He, Delong Ma, Jieyun Tang, Zejun Yi, Yanhui Yang, Yichi Lian

The Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, The


*Corresponding author Email: [email protected]

The Junggar Basin preserves a relatively complete record of Late Paleozoic strata and offers an important area to evaluate the tectono–depositional evolution of Junggar terrane. In this study, we focus on building Upper Paleozoic tectono-stratigraphic framework in the basin, trying to discuss their genetic mechanism and their tectono–depositional settings, and analyzing eruption time and depositional filling evolution, using geochronological and geochemical and geophysical data, in order to reveal the Late Paleozoic tectonic evolution of Junggar Basin and lay a foundation for oil-gas exploration.

Based on the zircon U–Pb ages obtained from the Junggar Basin, it can be inferred that seven periods of magmatic activity occurred during Late Paleozoic, including Devonian (398–392 Ma), Early Carboniferous (~355 Ma, 339–331 Ma and 325–322 Ma), Late Carboniferous (318–313 Ma and 309–300 Ma) and Early Permian (297–290 Ma). During Late Devonian to Early Carboniferous (>337 Ma), the Junggar Ocean and its branches (e.g., South Junggar Ocean and Karamaili Ocean) subducted northward beneath the Luliang arc and Wulungu terrane respectively, generating the subduction-related volcanic rocks. In the Early Carboniferous (337–322 Ma), the Junggar Oceanic lithosphere continued its northward subduction, whereas the Karamaili Ocean might have closed during this period like that in the East Junggar terrane, and the Luliang arc was

accreted into the previously formed Wulungu terrane. During the early Late Carboniferous (~318–313 Ma), the uplift and denudation resulting from amalgamation of Luliang arc and Wulungu terrane contributed the sediments (derived from Devonian to earliest Late Carboniferous ocean island arc) and minor subduction-related volcanic rocks which were deposited in the eastern Luliang Uplift. Meanwhile, the basin was in an extensional fault stage and controlled mainly by north-dipping normal fault probably because of slab rollback of the subducting Junggar Ocean. During middle to late Carboniferous (308–300Ma), continuing extension that resulted from rollback of the northward subduction zone gave rise to interaction between the metasomatized asthenospheric and sub-arc lithospheric mantle, and generated a fault-controlled intra-arc basin filled with Late Carboniferous tholeiitic basalts with some rhyolites in the eastern Luliang Uplift. Intra-arc basin contraction in Permian is probably indicative of the closure of Junggar Ocean in the northern Junggar Basin. Our study confirms the important role of subduction-accretion process associated with the Carboniferous crustal growth in the Junggar terrane.

Junggar basin is characterized by some subduction-related island arc basin systems with development of intra-arc basin and back-arc basin during Devonian–Carboniferous, formed collaged basement with Paleozoic juvenile crust

74

and minor pre-Cambrian basement in the Early Permian. After this, the Junggar Basin entered

the intracontinental evolution stage.

References

He, D.F., Li, D., Fan, C., Yang, X.F., 2013. Geochronology, geochemistry and tectonostratigraphy of Carboniferous strata of the deepest Well Moshen-1 in the Junggar Basin, Northwest China: insights into the continental growth of Central Asia. Gondwana Research 24, 560-577.

Li, D., He, D.F., Tang, Y., Fan, C., Kong, Y.H., 2012. Genesis of Early Carboniferous volcanic rocks of the Di'nan uplift in Junggar Basin: constraints to the closure time of Kalamaili Ocean. Acta Petrologica Sinica 28, 2340-2354 (in Chinese with English abstract).

Li, D., He, D.F., Qi, X.F., Zhang, N.N., 2013. How was the Carboniferous Balkhash – West Junggar remnant ocean filled and closed? Insights from the Well Tacan-1 strata in the Tacheng Basin, NW China. Gondwana Research. http://dx.doi.org/10.1016/j.gr.2013.10.003 (in press).

Li, D., He, D.F., Santosh, M., Tang, J.Y., 2014. Petrogenesis of Late Paleozoic volcanics from the Zhaheba depression, East Junggar: insights into collisional event in an accretionary orogen of Central Asia. Lithos 184-187, 167-193.

Xiao, W.J., Huang, B., Han, C., Li, J., 2010. A review of the western part of the Altaids: a key to understanding the architecture of accretionary orogens. Gondwana Research 18,

253-273. Xiao, W.J., Windley, B.F., Allen, M.F., Han, C.M.,

2013. Paleozoic multiple accretionary and collisional tectonics of the Chinese Tianshan orogenic collage. Gondwana Research 23, 1316-1341.

Xiao, W.J., M. Santosh, 2014. The western Central Asian Orogenic Belt: a window to accretionary orogenesis and continental growth. Gondwana Research 25, 1429-1444.

Yang, X.F., He, D.F., Wang, Q.C., Tang, Y., 2012.

Tectonostratigraphic evolution of the Carboniferous arc-related basin in the East Junggar Basin, northwest China: insights into its link with the subduction process. Gondwana Research 22, 1030-1046.

Yang, X.F., He, D.F., Wang, Q.C., Tang, Y., Tao, H.F., Li, D., 2012. Provenance and tectonic setting of the Carboniferous sedimentary rocks of the East Junggar Basin, China: evidence from geochemistry and U-Pb zircon geochronology. Gondwana Research 22, 567-584.

Pandian, M.S. (1999): Late Proterozoic acid magmatism and associated tungsten mineralization in NW India. Gondwana Research, v.2, pp.79-87.

Zachariah J K, Mohanta M K and Rajamani V (1996): Accretionary evolution of the Ramagiri Schist Belt, Eastern Dharwar Craton; Jour. Geol. Soc. India v. 47 pp. 279–291.



Abstract Volume


Metallogenic response to the destruction of the north

China Craton

Sheng-Rong Li, M. Santosh, Jun-Feng Shen, Guo-Chen Dong, Hong Xu, Ye Cao,

Wen-Yan Sun, Qing Li, Ju-Quan Zhang, Lin Li, Lin-Jie Zhang, Xiao Wang,

Qiongyan Yang

State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences,

China

The timing of Au-Ag-Mo-Cu-Fe-Pb-Zn metallogeny in the central North China Craton is constrained with zircon U-Pb, molybdenite Re-Os, pyrite/galena/sphalerite Rb-Sr，phlogopite and quartz Ar-Ar methods at 100-140 Ma (Li and Santosh, 2014;). The iron deposits in the southern Taihang Mountains mainly formed at 133-137 Ma (Li et al., 2013; Shen et al., 2013a,b). The gold and molybdenum in the central part of the craton formed at 127-131 Ma (Li et al., 2013; Li et al., 2014; Li Q et al., 2013; Sun et al., 2014b) whereas the silver-lead-zinc deposits formed at 100-102 Ma (Wang et al., 2014; Sun et al., 2014a). The copper and molybdenum in the northern Taihang region formed at ca.140 Ma (Dong et al., 2013). Ore genetic and geochemical studies reveal that the ore materials were mainly from the lower crust with different contents of mantle input. Our data show that the Fuping gold system witnessed greater mantle input than the Wu'an iron system (Li et al., 2013; Cao et al., 2012). The ore forming fluid shows magmatic signature, suggesting a close linkage between

the metallogeny and magmatism (Li et al., 2014). In conjunction with studies of the peripheral ore deposits, especially those from Jiaodong and Luxi, we suggest that the inhomogeneous thinning of the continental lithosphere during early Cretaceous triggered asthenospheric upwelling, crust-mantle decoupling, lower crust remelting, and mineralization (Li and Santosh, 2014; Guo et al., 2013; 2014; Yang et al., 2013a,b; Liu et al.,2014). We suggest that the junctions of three-microblock-boundaries in the North China Craton are potential locales for strategic ore-prospecting (Fig.1). Acknowledgments

This work was supported by NSFC (90914002), China Geological Survey (1212011220926, 12120114051101) and Special Research Fund For Doctoral Program of Higher Education [20130022110003]. This also is a contribution to the Talent Award to M. Santosh under the 1000 Talents Plan of the Chinese Government.

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Fig. 1 Schematic tectonic map of the North China Craton showing the locations of gold deposits and the junctions of three-microblock-boundaries.

References

Cao, Y., Carranza, E.J.M., Li, S.R.,Yao, M.J., Zhang, H.F.2012.Source and evolution of fluids in the Shihu gold deposit, Taihang Mountains, China: evidence from microthermometry, chemical composition and noble gas isotope of fluid inclusions. Geochemistry: Exploration, Environment, Analysis 12, 177–191.

Dong, G.C., Santosh, M., Li, S.R., Shen, J.F., Mo, X.X., Scott,S., Qu,K., Wang, X. 2013. Mesozoic magmatism and metallogenesis associated with the destruction of the North China Craton: Evidence from U-Pb geochronology and stable isotope geochemistry of the Mujicun porphyry Cu-Mo Deposit. Ore Geology Reviews 53,434-445.

Guo,P., Santosh, M., Li, S.R. 2013.Geodynamics of gold metallogeny in the Shandong Province, NE China: A geological and geophysical perspective. Gondwana Research, 24,1172-1202.

Guo, P., Santosh, M., Li, S.R., Li, Q. 2014. Crustal evolution in the central part of Eastern NCC: Zircon U-Pb ages from multiple magmatic pulses in the Luxi area and implications for gold mineralization, Ore Geology Reviews. Doi: 10.1016/j.oregeorev.2014.01.002.

Li, Q., Santosh, M., Li, S.R. 2013.Stable isotopes and noble gases in the Xishimen gold deposit, central North China Craton: metallogeny associated with lithospheric thinning and crust–mantle interaction. International Geology Review55,1728-1743.

Li, Q., Santosh, M., Li, S.R., Guo, P. 2014. The formation and rejuvenation of continental crust in the central North China Craton: Evidence from zircon U-Pb geochronology and Hf isotope, Journal of Asian Earth

Sciences. Doi: http://dx.doi.org/10.1016/j.jseaes.2014.02.022.

Li, S.R., Santosh M., Zhang, H.F., Shen, J.F., Dong, G.C., 2013, Inhomogeneous lithospheric thinning in the central North China Craton: Zircon U-Pb and S-He-Ar isotopic record from magmatism and metallogeny in the Taihang Mountains. Gondwana Research 23, 141-160.

Li, S.R., Santosh, M., 2014. Metallogeny and craton destruction: records from the North China Craton. Ore Geology Reviews 56, 376-414.

Li, S.R., Santosh, M., Zhang, H.F., Luo, J.Y.,

Zhang, J.Q., Li, C.L., Song, J.Y., Zhang, X.B., 2014.Metallogeny in response to lithospheric thinning and craton destruction: geochemistry and U-Pb zircon chronology of the Yixingzhai gold deposit, central North China Craton. Ore Geology Reviews. 56, 457-471.

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Liu, Y., Santosh, M., Li, S.R., Guo, P. 2014.Stable isotope geochemistry and Re–Os ages of the Yinan gold deposit, Shandong Province, northeastern China, International Geology Review. DOI: 10.1080/00206814.2014.886167.

Shen,J.F., Santosh,M., Li, S.R., Zhang, H.F., Yin, N., Dong, G.C., Wang, Y.J., Ma, G.G., Yu, H.J. 2013a.The Beiminghe skarn iron deposit, eastern China: Geochronology, isotope geochemistry and implications for the destruction of the North China Craton. Lithos, 156-159：218-229.

Shen J.F., Li S.R., Santosh M., Meng K., Dong G.C., Wang Y.J., Yin N., Ma G.G., Yu H.J. 2013b.He-Ar isotope geochemistry of iron and gold deposits reveals heterogeneous lithospheric destruction in the North China Craton. Journal of Asian Earth Sciences. http://dx.doi.org/10.1016/j.jseaes.2013.04.004

Sun, W.Y., Li, S.R., Santosh, M., Wang, X., Zhang, L.J. 2014. Isotope geochemistry and geochronology of the Qiubudong silver deposit, central North China Craton: Implications for ore genesis and lithospheric dynamics. Ore Geology Reviews57 (2014) 229–242.

Sun, W.Y., Li, S.R., Santosh, M., Zhang, X.Y.

2014. Isotope geochemistry and Re-Os

geochronology of the Yanjiagou Mo deposit in the central North China Craton. Geological Journal. DOI: 10.1002/gj.2563.

Wang, X., Li, S.R., Santosh, M., Gan, H.N., Sun, W.Y. 2014. Source characteristics and fluid evolution of the Beiyingxigou Pb-Zn-Ag deposit, central North China Craton: An integrated stable isotope investigation. Ore Geology Reviews56, 528-540.

Yang, Q., Santosh, M., Shen, J.F., Li, S.R. 2013a.Mesozoic magmatism and gold metallogeny in Jiaodong Peninsula, NE China: Zircon U-Pb geochronology, Lu-Hf isotopes and tectonic implications. Journal of Asian Earth Sciences 62: 537-546.

Yang, Q., Santosh, M., Shen, J.F., Li, S.R. 2013b. Juvenile vs. recycled crust in NE China: Zircon U –Pb geochronology, Hf isotope and an integrated model for Mesozoic gold mineralization in the Jiaodong Peninsula, Gondwana Research. http://dx.doi.org/10.1016/j.gr.2013.06.003.



Abstract Volume


Simian tectono–depositional evolution of Sichuan Basin

and adjacent areas

Yingqiang Li, Dengfa He *, Qinghua Mei, Jiao Li, Li Zhang

The Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, The


*Corresponding Author e-mail: [email protected]

The Simian is the first set of sedimentary cover deposited on the Yangtze para-platform, and as the most ancient natural gas reservoir ever discovered in China, some wells drilled in Weiyuan, Gaoshiti, and Anpingdian have tapped commercial gas flow in recent years. Thus the Simian in the Sichuan Basin has attracted great attention. Research on its tectono–depositional evolution lays an important foundation for oil and gas exploration. In this study, we focus on establishing a district sequence stratigraphic framework, documenting the sediment infill features, and analyzing their response to the tectonic evolution of the Sichuan Basin and adjacent areas. The data sets include comparison of seismic data, outcrop profiles, well drillings, inter-well correlations, spatial evolution of sedimentary facies, and their superposition with paleogeomorphology.

The Simian System in Sichuan Basin was divided into the Lower Simian Doushantuo Formation and the Upper Simian Dengying Formation. The Lower Simian Doushantuo Formation can be subdivided into four members, is composed of interbedded dolostone and mudstone, characterized by ‘black–white–black–white’ in hue from bottom to top. The Upper Simian Dengying Formation primarily consisting of algal dolomite, crystalline dolomite and grain dolomite, and can also be subdivided into four members. The rugged topography of the Yangtze craton was flattened under the effect of the continental ice sheet

glacial ploughing, when the basement of Simian carbonate was forming. During the depositional period of the Early Simian Doushantuo Formation, a suite of black shales with abundant phosphatic sediments were deposited under open water circulation. A large-scale carbonate platform deposition started in the Late Simian. From west to east, the sea level changed from shallow to deep, with the sediments changing from mudstone of residual land, carbonate platform and platform margin-slope eastwards, to siliceous rock of deep water basin. The strike of each facies belt is generally from southwest to northeast. During the depositional stage between the Member 1 and the middle of Member 2 of Dengying Formation, the study area was filled up by sediments. The flattened intracratonic uplift was forming on the intracratonic basin during the depositional periods between the end of Member 2 and the Member 3 of Dengying Formation. And during the Member 4 of Dengying Formation, the platform boundary shifted eastward with the decline of the sea level. Affected by two periods of Tongwan Movement, the Member 2 and Member 4 of Dengying Formation have been denuded to variable extents, some areas of the central basin formed palaeokarst unconformity. Formation and development of the Dengying Formation palaeokarst are closely related with reservoir, in which various sizes of primitive skeletal pores develop, and provide space for oil and gas accumulation.

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Fig. 1 Tectono–depositional environment of the Member 4 of Dengying Formation in Sichuan and adjacent areas.

References

Li, Y.Q., He, D.F., Went, Z., 2013. Palaeogeography and tectonic–depositional environment evolution of the Late Simian in Sichuan Basin and adjacent areas. Journal of Palaeogeography 15(2), 231–245.

Li, L., Tan, X.C., Zing, W., Zhou, T., Yang, Y., Hong, H.T., Lou, B., Bain, L.Z., 2013. Development and reservoir significance of

mud mounds in Simian Dengying Formation, Sichuan Basin. Petroleum Exploration and Development 40(6), 714–721.

Yuan, H.F., Liang, J.J., Gong, D.Y., CSU, G.S., Liu, S.G., Wang, G.Z., 2012.

Formation and evolution of Simian oil and gas pools in typical structures, Sichuan Basin, China. Petroleum Science 9(2), 129–140.



Abstract Volume


Spatial-temporal distribution and magma evolution of the

Early Permian Tarim large igneous province of NW

China

Zilong Lia, Yinqi Lia, Shufeng Yanga, Yu Xinga, Hanlin Chena, Siyuan Zoua, Haowei

Suna

aDepartment of Earth Sciences, Zhejiang University, Hangzhou 310027, P.R. China

The Early Permian Tarim Large Igneous Province (TLIP) in northwestern China, covering an area of ca. 250,000 square kilometers, is comparable to the Emeishan LIP in southwestern China. The lithological units in it are large volumes of flood basalts, layered intrusive rock, mica-olivine pyroxenite breccia pipe, and basic dike swarms, minor picrite and syenitic rocks as well as bimodal dykes. The spatial distribution of the TLIP from the spatial section lines, which shows the stratigraphic correlation among basaltic lava, tuff, interlayered mudstone, siltstone and sandstone and the thicknesses of the basaltic lavas from different field sections and drill holes, indicates widely distributed flood basaltic lavas in Tarim Basin. The Hf isotopic data suggest distinct sources for the basalts (290-285 Ma) and intrusive rocks (284-274 Ma) of the TLIP. The geochemical and Sr-Nd-Pb-Hf-PGE isotopic characterisation of the magma source of the basaltic lavas, development of large diabase swarms, minor picrite occurrence in the Tabe Uplift, and large scale mineralization associated Fe-Ti-V oxide deposit in Wajilitag area of Bachu County, all support the view that the Early Permian igneous units in Tarim Basin constitute a TLIP and has a genetic link with mantle plume activity. We argue that the basalts (290-285 Ma) were probably derived from a complicated

source in the lithospheric mantle by mainly lower degree of partial melting, having an interaction with asthenospheric (or plume) mantle, and that the mafic-ultramafic intrusive rocks (284-274 Ma) might be derived from the more deep primary magma, formed by fractional crystallization process. Acknowledgements

This study was funded by National Key Project for Basic Research of China (No. 2011CB808902, 2007CB411303) and Natural Scientific Foundation of China (No. 40930315).



Abstract Volume


Profiling mantle carbonate metasomatism using Os-Mg isotopes of Tibetan ultrapotassic magmatism

Dong Liua,*, Zhidan Zhaoa, Shan Kea, Elisabeth Widomb, Di-Cheng Zhua, Yaoling

Niua,c, Sheng-Ao Liua, Qing Wang1, Xuanxue Moa

aState Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and

Resources, China University of Geosciences, Beijing 100083, China bDepartment of Geology, Miami University, Oxford OH 45056, USA cDepartment of Earth Sciences, Durham University, Durham DH1 3LE, UK *Corresponding author e-mail: [email protected]

Mantle-derived magmatism at convergent plate boundary provides insights into the subduction and recycling of sediments. Using Os-Mg isotopes, we present a systematic study on the Miocene ultrapotassic rocks in southern Tibet, aiming to investigate the metasomatic events in mantle region. The dichotomy for the correlation between Os and Mg isotopes indicates different processes that control the generation of ultrapotassic rocks. The positive co-variations between 187Os/188Os and 1/Os imply that crustal assimilation was experienced by the Tibetan ultrapotassic rocks, which is consistent with evidence from zircon xenocrysts with pre-eruptive ages entrained in ultrapotassic magmas. However, the high MgO concentrations of ultrapotassic rocks give rise to higher ‘resistance’ for Mg isotopes to crustal assimilation with respect to Os isotopes, suggesting the potential of Mg isotopes of ultrapotassic rocks in recognizing mantle metasomatism. The correlations between δ26Mg and Hf/Sm in ultrapotassic rocks with mantle-like 187Os/188Os corroborate the mantle carbonate metasomatism, which can be further modeled by 10-15 % carbonates recycled into spinel-facies peridotite. In addition, the relationship between decreasing δ26Mg and

increasing Th/U require a high Th/U and high carbonatitic clinopyroxene abundant mantle source region, which is possibly caused by carbonate melt metasomatism. Systematic variations of δ26Mg, Hf/Sm, and Th/U in ultrapotassic rocks, which are outcropping from south to north in western Lhasa terrane, correlate well with the devolatilization processes changing from metamorphic dehydration to melting regime with more carbonates buried in the deep mantle away from suture zones. Overall, this work highlights the significant contribution of marine sediment metasomatism during the northward subduction of the Neo-Tethyan oceanic slab in generating the Tibetan ultrapotassic rocks.




Abstract Volume


The biostratigraphic succession of acanthomorphs of the Ediacaran Doushantuo Formation in the Yangtze Gorges area, South China and its international correlation

Pengju Liu

Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China *Corresponding author e-mail: [email protected]

Large, Ediacaran acanthomorphic acritarchs are now known from several basins in the world. Some globally distributed taxa with short and well-documented stratigraphic ranges provide potential tool for biostratigraphic subdivision and global correlation of Ediacaran strata.

The Yangtze Gorges area of South China is one of the most important locations for studying Ediacaran successions. Abundant acanthomorphic acritarchs had been found from the Ediacaran Doushantuo Formation. The stratigraphic distribution of acritarchs at several sections has allowed two assemblages of acanthomorphic acritarchs (lower Tianzhushania spinosa assemblage and upper Hocosphaeridium anozos - Hocosphaeridium scaberfacium – Tanarium conoideum assemblage) to be established. These two assemblages, which are found in the lower (Member II) and the upper (Member III) Doushantuo Formation, respectively, are constrained stratigraphically to the intervals of the first and the second positive δ13C excursions (EP1 and EP2), respectively, and are separated by an interval of second negative δ13C excursion (EN2).

The lower assemblage is dominated by the taxon Tianzhushania spinosa. Apart from South China, the taxon Tianzhushania spinosa has been found from northern India (personal communication between Dr. Chongyu Yin and

Dr. Harshita Joshi), which suggest that the lower Tianzhushania spinosa assemblage is equal to the acanthomorphic assemblage in northern India.

By comparison with the lower Tianzhushania spinosa assemblage, the upper assemblage comprises more acanthomorphic acritarchs both in terms of the number of specimens and in the diversity of the species. Fifteen species, Appendisphaera clava, A. crebra, A.? hemisphaerica, A. longispina, A. magnificum, A. setosa, Eotylotopalla delicata, Hocosphaeridium anozos, H. scaberfacium, Knollisphaeridium maximum, Mengeosphaera constricata, Schizofusa zangwenlongii, Sinosphaera rupina, Xenosphaera liantuoensis, Variomargosphaeridium floridum, are the predominant species in upper assemblage, among them, the nominal taxa Hocosphaeridium anozos, and H. scaberfacium occur in greatest numbers and throughout the assemblage, whereas the species Tianzhushania spinosa is presumed to have become extinct. Previous biostratigraphic studies indicated that the upper assemblage of the Doushantuo Formation in the Yangtze Gorges area of South China can be correlated with the Ediacaran Complex Acanthomorphic Palynoflora (ECAP) of Australia. Similarly, many taxa from the upper acanthomorphic assemblage in the Yangtze Gorges area have been reported from Siberia and

83

the East European Platform. Coupled with previously reported data, taxa of the upper assemblage in the Yangtze Gorges area that are also found from the Ediacaran successions in Siberia and the East European Platform include Appendisphaera tenus, Cavaspina acuminata, C. basiconica, Ceratosphaeridium glaberosum, Eotylotopalla delicata, E. strobilata, Hocosphaeridium scaberfacium, H. anozos,

Knollisphaeridium maximum, K. triangulum, Schizofusa zangwenlongii, Tanarium pilosiusculum, Variomargosphaeridium floridum, and Weissiella grandistella, demonstrating that the upper assemblage in the Yangtze Gorges area is stratigraphically correlative with those from Siberia and the East European Platform.



Abstract Volume


Crustal carbonatite dykes within Tibetan plateau:

Implications to global climate change

Yan Liu

State Key Laboratory of continental tectonics and dynamics, Institute of Geology, Chinese Academy of

Geological Sciences, Beijing, 100037 *Corresponding author e-mail: [email protected]

Global climate change has become one of the hottest issues worldwide. Knowledge of ancient Earth’s surface temperature is critical to understanding Earth’s surface temperature changing in the near future, as well as evaluating effect of mankind’s carbon emissions exactly. Numerous studies suggest that Earth’s surface temperature has decreased since the end of the Eocene (e.g., Raymo and Ruddiman, 1992; Zachos et al., 2008; Sun et al., 2009; Scher et al., 2011). It is generally accepted that the long-term global cooling in the past 50 Myr is a consequence of long-term decrease of global CO2 concentrations, and thus, decreasing the natural greenhouse effect (e.g., Arrhenius, 1896; Chamberlin, 1899; Zachos et al., 2008; Beerling and Royer, 2011). However, it is still poorly-known where and how huge amounts of atmospheric CO2 have been sunk since the end of Eocene (e.g., Sundquist, 1993). If the question remains obscure, then a currently popular hypothesis that global warming is largely driven by carbon emissions of mankind lacks solid evidence.

Since the Cenozoic, the Indian continent has continuously moved northwards and collided with the Asian continent finally, leading to the close of the larger Neo-Tethyan Ocean and subsequent uplift of Himalayan Mountains, as well as formation of Tibetan plateau. A ‘Raymo’ hypothesis that the uplift of the Himalayan-Tibetan region, enhancing chemical weathering,

would absorb huge amounts of atmospheric CO2 and subsequently cool Earth was present at long time ago (e.g., Raymo and Ruddiman, 1992). This hypothesis accounts for the processes linking climate change with uplift of high terrains in the past 50 Myr roughly. However, this hypothesis has been recently challenged by the studies of degassing of hot springs within Himalayan Mountains, suggesting that Himalayan Mountains are carbon sources (Becker et al., 2008; Gaillardet and Galy, 2008). These arguments clearly illustrate that traditional studies on Earth’s surface carbon cycling hardly satisfy demands of current society. In this study, the role of Tibetan plateau in carbon recycling between Earth interior and exterior is re-evaluated based on intensive geological survey.

Geological investigations have recently revealed that numerous carbonate dykes have intruded granite and/or granulites along large fault zones within the Tibetan plateau (Liu, 2013). Distinctive alteration halos separate the carbonate dykes from the country rocks. CO2 and water inclusions are distinguished within the carbonate minerals of the dykes. Geochemically, these dykes are markedly different from a majority of mantle-derived carbonatites, and similar to sedimentary carbonate rocks. Therefore, these dykes are

85

regarded as crustal carbonatite dykes, a new kind of igneous rocks.

Previous studies have illustrated that eastern Greater Himalayan Crystallines were finally formed by flat-subducted Indian continental slabs beneath Tibetan plateau (e.g., Liu and Zhong, 1997; Neogi et al., 1998; Daniel et al., 2003; Liu et al., 2007a; 2007b). After dehydration and decarbonation, flat-subducted Indian continental slabs have been transformed into portions of thickened crust of Tibetan plateau. At the same time, Tibetan regions started to uplift and proto-plateau was formed, experiencing chemical weathering. During sequential collision between Indian and Asian continents, the portions of previously thickened crust of south Tibetan plateau were exhumed to become the eastern Greater Himalayan Crystallines by tectonics and chemical weathering, consuming huge amounts of atmospheric CO2. The erosion products were mainly deposited in foreland basins, such as Ganges foreland basin, to form carbon-rich formations, for example, Siwalik formation. These carbon-rich formations, at the

expense of huge amounts of atmospheric

CO2, have been subsequently transferred into the interior of Tibetan plateau along with flat-subducted continental slabs. Some carbon from the buried carbon-rich formation beneath Tibetan plateau has been released back to the atmosphere through hot springs. Most carbon had, however, been transferred into the deep interior of the Tibetan plateau. Micas within the subducted continental slabs underwent dehydration to form granitic magmas and high-pressure granulites beneath Tibetan plateau. Metasomatic reactions between the granitic magmas and the subducted carbonates within the carbon-rich formation took place to form skarns, also regarded as calc-aluminosilicate rocks, and released high-temperature CO2-rich fluids, beneath the Tibetan plateau. The high-pressure granulites and skarns are normally observed at the eastern Greater Himalayan Crystallines. Ferric iron in the biotite is further reduced by the carbon of the buried formation during the dehydration, also releasing high-temperature CO2-rich fluids beneath the Tibetan plateau. The CO2-rich fluids are regarded as crustal carbonatite magmas in this study. The magmas/fluids intruded into Tibetan upper crust

Fig. 1 Simplified crustal section of Tibetan region showing carbon recycling between Tibetan interior

and exterior during collision between India and Asia.

86

to form crustal carbonatite dykes finally. Carbon recycling between Tibetan interior and exterior is thus shown in Fig. 1. The huge amounts of atmospheric CO2 have, therefore, been transformed into crustal carbonatite magmas within thickened crust of Tibetan plateau during the collision between India and Asia. The carbon emitted by hot springs as well as volcanoes within Tibetan plateau was originated from the atmosphere. It is recycling carbon. The carbon emissions from the Tibetan plateau are slightly less than those sunken by Tibetan plateau. Otherwise, the crustal carbonatite dykes, formed

by consuming huge amounts of atmospheric CO2, would have never occurred within the Tibetan plateau. The fact that crustal carbonatite dykes are distinguished within Tibetan plateau clearly suggests that Tibetan plateau is a huge reservoir for atmospheric CO2, leading to global cooling in the past 50 Myr. Moreover, the changing of atmospheric CO2 was mainly driven by Earth’s tectonic activities. Global climate change is, therefore, just a natural phenomenon and not as a result of human activities.

References

Arrhenius, S., 1896 On the influence of carbonic acid in the air upon the temperature on the ground. Philosophical Magazine 41, 237-279.

Becket, J. A., Bickle, M. J., Galy A., Holland, T. J. B., 2008 Himalayan metamorphic CO2 fluxes: Quantitative constraints from hydrothermal springs. Earth Planetary Science Letters 265, 616-629.

Beerling, D. J., Royer, D. L., 2011 Convergent Cenozoic CO2 history. Nature Geosciences 4, 418-420.

Chamberlin, T. C., 1899 An attempt to frame a working hypothesis of the cause of glacial periods on an atmospheric basis. Journal of Geology 7, 545-584, 667-685, 751-787.

Daniel, C. G., Hollister, L. S., Parrish, R. R., Grujic, D., 2003 Exhumation of the Main Central Thrust from lower crustal depths, Eastern Bhutan Himalaya. Journal of Metamorphic Geology 21, 317-334.

Gaillardet, J., Galy, A., 2008 Himalaya-Carbon sink or source? Science 320, 1727-1728.

Liu, Y., 2013 Petrogenesis of carbonic dykes within southern Tibetan plateau, and climatic effects. Chinese Journal of Geology 48(2), 384-405 (in Chinese with English abstract)

Liu, Y., Berner, Z., Massonne, H-J., Zhong, D., 2006 Carbonatite-like dykes from the eastern Himalayan syntaxis: Geochemical, isotopic,

and petrogenetic evidence for melting of metasedimentary carbonate rocks within the orogenic crust. Journal of Asian Earth Sciences 26, 105-120.

Liu, Y., Siebel, W., Massonne, H.-J., Xiao X., 2007a Geochronological and petrological constraints for the tectonic evolution of the

central Greater Himalayan Sequence in the Kharta area, southern Tibet. Journal of Geology 115, 215-230.

Liu, Y., Yang, Z., Wang, M., 2007b History of zircon growth in a high-pressure granulite within the eastern Himalayan syntaxis, and tectonic implications. International Geology Review 49, 861-872.

Liu, Y., Zhong, D. L., 1997 Petrology of high-pressure granulites from the eastern Himalayan syntaxis. Journal of Metamorphic Geology 15, 451-466.

Neogi, S., Dasgupta, S., Fukuoka, M., 1998 High-P–T polymetamorphism, dehydration melting, and generation of migmatites and granites in the Higher Himalayan Crystalline Complex, Sikkim, India. Journal of Petrology 39, 61-99.

Raymo, M. E., Ruddiman, W. F., 1992 Tectonic forcing of late Cenozoic climate. Nature 359, 117-122.

Scher, H. D., Bohaty, S. M., Zachos, J. C., Delaney, M. L., 2011 Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene−Oligocene transition. Geology 39, 383–386.

Sun, B., Siegert, M. J., Mudd, S. M., Sugden, D., Fujita, S., Cui, X. B., Jiang, Y. Y., Tang, X. Y., Li, Y. S., 2009 The Gamburtsev mountains and the origin and early evolution of the Antarctic ice sheet. Nature 459, 690-692.

Sundquist, E. T., 1993 The global carbon dioxide budget. Science 259, 934-941.

Zachos, J. C., Dickens, G. R., Zeebe, R. E., 2008 An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics. Nature 451, 279-283.

Pandian, M.S. (1999): Late Proterozoic acid

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magmatism and associated tungsten mineralization in NW India. Gondwana Research, v.2, pp.79-87.

Zachariah J K, Mohanta M K and Rajamani V

(1996): Accretionary evolution of the Ramagiri Schist Belt, Eastern Dharwar Craton; Jour. Geol. Soc. India v. 47 pp. 279–291.



Abstract Volume


The tantalum pegmatite deposits of Belogorskoye and

Yubileinoye, Kazakhstan

I.Mataibayevaa, R.Seltmannb, V.Shatovc

aEast Kazakhstan State Technical University, Ust-Kamenogorsk, Kazakhstan, [email protected] bCERCAMS, Department of Earth Sciences, Natural History Museum, London, UK, [email protected] cA.P. Karpinsky Russian Geological Research Institute, Saint Petersburg, Russia

The Belogorskoye and Yubileinoye tantalum pegmatite deposits of Kalba region are located in the northwestern part of the Kalba-Narym belt (Eastern Kazakhstan), a terrane which docked with the Greater Altai during the Lower Carboniferous. It is separated from the neighbouring Rudny Altai and Western Kalba zones by tectonic boundaries with a northwesterly direction, these are the Irtysh shear zone and the Zapadno-Kalbinsky deep fault, respectively. Rare-metal mineralization is heterochronous and polygenic and is genetically related to the formation of the Kalbinsky batholith which has a complicated architecture. The country rocks of the batholith are terrigenous-sedimentary flysch of Upper Devonian-Lower Carboniferous age (Daukeev et al., 2004).

The Belogorsko-Baimurskoye pegmatite field lies on the south-eastern exocontact of the Tastyubinsko-Chebundinsky stock. The ore field includes two deposits of different types: the Belogorskoye beryl-tantalite deposit and the Verkhne-Baimurzinskoye spodumene-Sn-Ta deposit. In the footwall of the deposits there are a third and fourth suite of pegmatites with lower productivity.

Belogorskoye deposit. The principal ore minerals are tantalite, beryl and cassiterite. Veins can be traced to a depth of 500-700 m. The

average grade of tantalum in the deposit is 0.0087%; the tin grade is 0.011%. Reserves are 243 t of Ta2O5, and 224 t of Nb2O5 (Daukeev et al., 2004).

The Verkhne-Baimurzinskoye deposit is formed by the Osnovnaya vein with a thickness up to 8.2 m and a length reaching 2.5 km. The main rock-forming minerals are quartz, microcline, albite, spodumene, and muscovite with accessory phosphates of Fe and Mn, schorl and garnet. Ore minerals are beryl, tantalite-columbite, cassiterite. The vein is divided into small blocks by numerous faults. Other rare-metal bearing pegmatite veins are characterized by smaller sizes and poorer mineralization. Reserves of tantalum are 195 t at an average grade of 78.02 g/t (Daukeev et al., 2004).

The Yubileinoye deposit. There are 11 mineral paragenetic associations in the pegmatites including five formed as a result of ‘primary crystallization’ – 1) quartz-microcline, 2) quartz-microcline-albite, 3) microcline in blocks, 4) quartz-spodumene, 5) fine-grained albite, the rest being products of autometasomatic replacement (Daukeev et al., 2004).

Generalized model of pegmatite formation. Pegmatites are produced by crystallization of the magmatic-hydrothermal residual melts and formed at the late stage of



89

evolution of particular volatile-enriched phases of magmatic intrusions. Formation of pegmatites takes place in three stages – magmatic, super-critical (‘pneumatolytic’) and hydrothermal. During crystallization of rare-metal-pegmatites, crystallization of the residual pegmatite melt can cover the temperature range from 750 to below 150oC, and the pressure range from 2500 bar to below 500 bars. The presence of numerous rare-metal pegmatites throughout the Kalbaore fields indicates that pegmatite melts were generated from different independent pegmatite sources with subsequent

differentiation of the pegmatite melt-solution within separate pegmatite bodies.

Acknowledgements

This is a contribution to IGCP-592.

References

Daukeev, S. Zn., Ushkenov,B.S., Bespaev,Kh.A., Miroshnichenko, L.A., Mazurov,A.K., Sayduakasov M.A., Eds., 2004. Atlas of mineral deposit models of the Republic of Kazakhstan, 141 p.



Abstract Volume


Lonely wanderers and Gondwana

Joseph G. Meert

Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL,

USA 32611 *Corresponding author e-mail: [email protected]

The observation is made that there are very strong similarities between the geometries of the supercontinents Columbia (Rogers and Santosh, 2002; Zhao et al., 2002), Rodinia (Torsvik et al., 1996; Li et al., 2008) and Pangea (Torsvik et al., 2012; Meert, 2014). If plate tectonics was operating over the past 2.5 billion years of Earth history, and dominated by extroversion and introversion of ocean basins, it would be unusual for three supercontinents to resemble one another so closely. The term ‘strange attractor’ is applied to landmasses that form a coherent geometry in all three supercontinents. Baltica, Laurentia and Siberia form a group of ‘strange attractors’ as do the elements of East Gondwana (India, Australia, Antarctica, Madagascar). The elements of ‘West Gondwana’ are positioned as a slightly looser amalgam of cratonic blocks in all three supercontinents and are referred to as ‘spiritual interlopers’. Relatively few landmasses (the South China, North China, Kalahari and perhaps Tarim cratons) are positioned in distinct locations within each of the three supercontinents and these are referred to as ‘lonely wanderers’.

There may be several explanations for why these supercontinents show such remarkable similarities. One possibility is that modern-style

plate tectonics did not begin until the Late Neoproterozoic and horizontal motions were restricted and a vertical style of ‘lid tectonics’ dominated. If motions were limited for most of the Proterozoic, it would explain the remarkable similarities seen in the Columbia and Rodinia supercontinents, but would still require the strange attractors to rift, drift and return to approximately the same geometry within Pangea.

A second possibility is that our views of older supercontinents are shaped by well-known connections documented for the most recent supercontinent, Pangea. It is intriguing that three of the four ‘lonely wanderers’ (Tarim, North China, South China) did not unite until just before, or slightly after the breakup of Pangea. The fourth ‘lonely wanderer’, the Kalahari (and core Kaapvaal) craton has a somewhat unique Archean-age geology compared to its nearest neighbors in Gondwana, but very similar to that in Western Australia.

In this paper, I will discuss possible links between the lonely wanderers (North China craton, the Tarim craton and the South China craton) with East Gondwana (strange attractors). Specifically, I will detail potential links between Tarim, North China, South China with India.


91

Fig. 1 Lonely wanderers (South China, Tarim, North China and Kaapvaal/Kalahari) within the three supercontinents of Columbia, Rodinia and Pangea).

References

Li, Z. X., Bogdanova, S. V., Collins, A. S., Davidson, A., De Waele, B., Ernst, R. E., Fitzsimons, I. C. W., Fuck, R. A., Gladkochub, D. P., Jacobs, J., Karlstrom, K. E., Lu, S., Natapov, L. M., Pease, V., Pisarevsky, S. A., Thrane, K., and Vernikovsky, V., 2008, Assembly, configuration, and break-up history of Rodinia: A synthesis. Precambrian Research, 160, 179-210

Meert, J.G., Strange Attractors, 2014. Spiritual Interlopers and Lonely Wanderers: The Search for Pre-Pangæan Supercontinents. Geoscience Frontiers, 5, 155-166.

Rogers, J.J.W. and Santosh, M., 2002.

Configuration of Columbia, a Mesoproterozoic supercontinent, Gondwana Research, 5, 5-22.

Torsvik, T.H., Van der Voo, R., Preeden, U., MacNiocaill, C., Steinberger, B., Doubrovine, P.V., van Hinsbergen, D.J.J., Domeir, M., Gaina, C., Tohver, E., Meert, J.G., McCausland, P.J.A., Cocks, R.M., 2012. Phanerozoic polar wander, palaeogeography and dynamics, Earth Science Reviews, 114, 325-368.

Zhao, G., Cawood, P.A., Wilde, S.A., Sun, M., 2002. Review of global 2.1-1.8 Ga orogens: Implications for a pre-Rodinia supercontinent, Earth-Science Reviews, 59, 125-162.



Abstract Volume


Structural geometric and kinematic features and

deformation mechanism of west segment of South Daba

Shan

Qinghua Mei1, Dengfa Hea*, Longbo Chena, ZhuWena,b, Li Zhanga, Yingqiang Lia

aThe Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, the

Ministry of Education, China University of Geosciences, Beijing 100083, China bChongqing Institute of Geology and Mineral resources, Chongqing 400042, China *Corresponding author e-mail: [email protected]

The fine interpretations of seismic profiles in the west segment of South Daba Shan, which is located at front of South Daba Shan foreland fold-and-thrust belt, are instructive in studying the intracontinental tectonic deformation after the Qinling orogen collided with Yangtze block as well as in the petroleum exploration of Northeastern Sichuan Basin. This paper, based on the latest pre-stack depth migration 3D seismic data, combined with 2D seismic data, well data, and outcrop geologic data, finely depicts the structural, geometric and kinematic features of the west segment of South Daba Shan with the application of fault-related folding geometry principles. Three sets of main detachment layers are developed at the west segment of South Daba Shan, i.e., Lower Triassic Jialingjiang Formation gypsolith interval, Silurian mudstone zone and Cambrian shale bed. Controlled by them, the structure presents a feature of multi-level detachment deformation in the west segment of South Daba Shan. The upper thrust system is controlled by Jialingjiang Formation gypsolith detachment layer and presents a Jura-like fold structural style. The middle thrust system takes Silurian detachment layer as floor decollement surface and Jialingjiang Formation gypsolith interval as roof decollement surface, in which imbricate

structural style is formed, and basinward imbricate thrusting predominates. The lower thrust system is confined between Cambrian detachment layer and Silurian detachment layer, in which imbricate structural style is also formed; imbricate structure is mainly developed in South Daba Shan front belt, and up-dip imbricate thrusting predominates, which results in the passive uplift of overlying structural layer. The Sinian and Proterozoic basement below Cambrian detachment layer spread horizontally, and basically have not participated in deformation. Based on the tectonic deformation features of the west segment of South Daba Shan, combined with the analysis test results of the predecessors, we believe that the tectonic evolution from Daba Shan to the Sichuan Basin has an uplifting migrating characteristic. This paper divides the tectonic evolution of the study area into four stages, i.e., first stage (150–110 Ma): Late Jurassic–Cretaceous initial tectonic deformation stage; second stage (110–70 Ma): Late Cretaceous tectonic deformation development stage; third stage (70–30 Ma): Paleogene tectonic continuous development stage; and fourth stage (30 Ma–nowadays), Neogene violent tectonic uplifting and adjusting–shaping stage. We use critical-taper structural wedge theory to show the deformation

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mechanism of South Daba Shan，and South Daba Shan exhibits a low taper. Combined with magnetotelluric profile and deep seismic profile, we argue that the tectonic deformation

mechanism of the west segment of South Daba Shan is mainly controlled by slab pull of Yangtze plate subduction zone and the multi-level detachment system (Fig.1).

Fig. 1 Intracontinental subduction model with multi-level detachment deformation. ZBF - Zhenba Fault; CKF - Chenkou Fault; AK F- Ankang Fault; SDF - Shangdan Fault; LCF - Luanchuan Fault; LSF - Lushan Fault.

References

Bilotti F., and Shaw J. H., 2005. Deep-water Niger Delta fold and thrust belt modeled as a critical-taper wedge: The influence of elevated basal fluid pressure on structural styles: American Association of Petroleum Geologists Bulletin, 89: 1475-1491.

Dong, S.W., Gao, R., Yin, A., et al., 2013. What drove continued continent-continent convergence after ocean closure? Insights from high-resolution seismic-reflection profiling across the Daba Shan in central China. GEOLOGY, 41(6):671–674.

Dong, Y.P., Shen, Z.Y., Xiao, A.C., et al., 2011.Construction and structural analysis of regional geological sections of the southern Daba Shan thrust-fold belts.

Acta Petrologica Sinica, 27( 3) : 689-698. Dong, Y.P., Liu, X.M., Zhang, G.W., et al., 2012.

Triassic diorites and granitoids in the Foping area: Constraints on the conversion from subduction to collision in the Qinlingorogen, China. Journal of Asian Earth Sciences,47:123–142.

He, D.F., SUPPE, J., Jia, CH.Z., 2005. New advances in theory and application of fault related folding. Earth Science Frontiers, 12(4):353-364.

Li, Z.W., Liu, S.G., Luo, Y.H., et al., 2006.Structural style and deformational mechanism of southern Dabashan foreland fold-thrust belt in central China. Geotectonica et Metallogenia, 30(3): 294-304.



Abstract Volume


The Alpine Triassic development in the Southern

Carpathians (Romania)

Mihaela C. Melinte-Dobrinescua and Relu-Dumitru Robanb

aNational Institute of Marine Geology and Geo-ecology (GEOECOMAR), Bucharest, Romania, e-mail:

[email protected] bUniversity of Bucharest, Faculty of Geology and Geophysics, Bucharest, Romania, e-mail:

[email protected]

The Romanian Carpathians represent an arcuate belt formed in response to the Triassic up to Tertiary evolution of three continental blocks: (i) Tisia, which is composed of the Inner Dacide nappes, (ii) Dacia made up by the Median Dacide nappes, and (iii) the Eastern European-Scythian-Moesian platforms. These three blocks were separated by two oceanic domains which evolved during the extensive stage of Carpathians, being deformed and involved in the Transylvanide and Pienide tectonic units (Săndulescu, 1984; Csontos & Vörös, 2004).

The Median Dacides are mainly composed of the Getic and Supragetic nappes (Săndulescu, 1988) that contain widespread Triassic deposits, in Alpine facies, especially in the eastern part of the Southern Carpathians. It is to be mentioned that several significant Triassic territories of the world have been described in the Alpine and Carpathian belts. For this reason, some Triassic successions of these regions (i.e., in Austria, N Italy and Romania) have been proposed as GSSP (Global Stratotype Section and Point) for several Triassic stages.

During the Middle Triassic, a broad carbonate ramp developed at the western end of the Tethys Ocean, including the Carpathian area. In the Southern Carpathians, the Middle Triassic is in general characterized by the presence of the Guttenstein facies, i.e., light-grey dolomite and

rose dolomite with intercalations of hematite. The fossil content consists of rare bivalves, ostracods, crinoids, sponge spicules and radiolarians (Bleahu et al., 1994; Dumitrică, 2004) similar to those found in the Guttenstein Formation of the Alps (Tollmann, 1976; Krystyn and Lein, 1996).

The Late Triassic of the Southern Carpathians is mainly characterized by the deposition of limestones, Hallstatt type. Few calcareous nanofossils, poorly preserved, belonging to the taxa Crucihabdus primus, Archaeozygodiscus sp., Prinsiosphaera triassica and Orthopithonella spp., together with a variety of calcispheres and broken tests of calcareous dinoflagellates have been encountered. Rarely, macrofaunas, i.e., ammonites and bivalves, have been observed.

References

Bleahu, M., Haas, J., Kovács, S., Péró, Cs., Mantea, G., Bordea, S., Panin, S., Bérczi-Makk, A. Stefánescu, M., Konrád, Gy., Nagy, E., Rálisch-Felgenhauer, E., Sikic, K., Török, Á., 1994. Triassic facies types, evolution and paleogeographic relations of the Tisza Megaunit. Acta Geol. Hung. 37/3–4, 187–234.

Csontos L, Voros A, 2004. Mesozoic plate tectonic reconstruction of the Carpathian region. Palaeogeography, Palaeoclimatology, Palaeoecology 210, 1-56.

Dumitrică, P., 2004. New Mesozoic and early Cenozoic spicular Nassellaria and

Nassellaria-like Radiolaria Revue de Micropaléontologie 47, 193-224.

Krystyn, L., Lein, R., 1996. Triassische. Field Guide, Sediment ’96 Meeting. Exkursion A4, Wien.

Săndulescu, M. 1984. Geotectonica României. Editura Tehnică, Bucureşti, 336 pp.

Săndulescu, M. 1988. Cenozoic tectonic history of the Carpathians. In: Royden, L.H. and Horvath, F. (Eds.), The Pannonian Basin: a study in basin evolution. AAPG Mem. 45, 17-26.

Tollmann, A., 1976. Analyse des klassischen nordalpinen Mesozoikums. Franz Deuticke, Wien, pp. 65–81.



Abstract Volume


Sulfide associations in diamond-grade dolomitic marble from the Kokchetav massif (Northern Kazakhstan): Evidence for the sulfide melt presence at the UHP-conditions

Anastasia O. Mikhnoa,b, Xiao-Ying Gaoc, Andrey V. Korsakova,b

aInstitute of Geology and Mineralogy SB RAS, Koptyug Pr. 3, Novosibirsk 630090, Russia,

E-mail:[email protected] bNovosibirsk State University, Pirogova St. 2, Novosibirsk-630090, Russia cSchool of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026,

China

The Kokchetav massif of northern Kazakhstan is part of an intracontinental orogenic belt between former Laurasian and Gondwana continents (Schertl and Sobolev, 2013). It represents an approximately 17 km wide and 80 km long mega melange zone which was a slice of the continental crust exhumed from depths of at least 120 km (Dobretsov et al., 1995). Deeply subducted rocks from the Kokchetav massif were recrystallized within the diamond-stability field (P = 6-7 GPa, T = 1000 °C) and preserve evidence for ultrahigh pressure melts (Hermann et al., 2006, Korsakov and Hermann, 2006, Mikhno and Korsakov, 2013).

Presence of aqueous fluid, carbonate and silicate melts testify the heterogeneity of rock-forming media of UHPM rocks of Kokchetav massif (Hermann et al., 2006). Korsakov et al. (2006) and Hermann et al. (2006) suggested the presence of sulfide melts in the clinozoisite gneisses and dolomitic marbles based on ‘decrepitated’ inclusions of sulfides in garnets and the reaction textures. However their P-T conditions remain poorly constrained. Herein, we present preliminary results of our ongoing

research: (i) investigation of sulfide associations in the dolomitic marble of the Kokchetav massif, (ii) evidence for the presence sulfide melts at the UHP conditions.

The rock-forming minerals of the dolomitic marbles are represented by calcite, dolomite, garnet and clinopyroxene. Zircon, diamond, graphite, allanite, phengite, titanite, pyrite, pyrrhotite, chalcopyrite were identified as accessory minerals. Multiphase inclusions in garnet porphyroblasts could be subdivided into two groups – carbonate-sulfide and carbonate-Kfs-allanite inclusions. Carbonate-sulfide inclusions are composed of pyrrhotite, pyrite, dolomite and calcite. These inclusions show decrepitation features at the sulfide parts of inclusions and never at the carbonate part (Fig.1). Some of these inclusions as well as some garnet porphyroblasts are surrounded by clinopyroxene-spinel symplectite.

Carbonate-Kfs-allanite inclusions show zoning structure: cores of inclusions represented by Mg-calcite are subsequently mantled by allanite and Kfs. Similar allanite-Kfs structure occurs at the contact of garnet porphyroblasts with Mg-Calcite matrix. Pyrrhotite was

97

identified in the matrix closely coexisting with allanite.

Most likely, sulfide-carbonate inclusions were originally captured as immiscible sulfide and carbonate melts. This fact is supported by decrepitation features of sulfide-carbonate inclusions and the experimental study of sulfide-carbonate systems (Schushkanova et al., 2008). Findings of sulfide-carbonate inclusions with the rim of clinopyroxene-spinel symplectite reveal that these inclusions were captured at least at 1.8 GPa and 900 °C (Sobolev et al., 2006). Allanite-Kfs rims could be interpreted as the result of reaction on the contact of carbonatite melt with

garnet porphyroblasts. Minimum PT-conditions of 3.1 GPa and 950 °C were estimated by the intersection of the Kokchetav PT-path and allanite stability field. Therefore, presence of pyrrhotite in close coexistence with allanite would imply existence of sulfide melt under UHP conditions in carbonate rocks of the Kokchetav massif. Acknowledgements

This study was supported by RFBR grants No. 14-05-31465 and No. 13-05-00367and MD-1260.2013.5.

Fig. 1 (a) Scanning electron microphotograph (SEM) of Kfs-Allanite texture at the contact of garnet porphyroblast

and Mg-calcite. (b) SEM of the sulfide-carbonate inclusion with the decrepitation features in garnet porphyroblast.

(c)-(d) SEM photograph of allanite closely coexisting with pyrrhotite. (e) PT-path for the Kokchetav massif: solid

black line – Mikhno and Korsakov (2013), black dashed line – Hermann et al. (2001),blue dash-dotted line –

Dobretsov and Shatsky (2004), allanite stability field – (Hermann, 2002), other lines were taken from Mikhno et

al. (2013). Mg-cal –Mg-calcite, Dol – dolomite, All – allanite, Po – pyrrhotite, Grt – garnet, Cpx+Spl –

clinopyroxene-spinel symplectite, Sulf – sulfide.

References

Dobretsov, N.L., Shatsky, V.S., 2004. Exhumation of high-pressure rocks of the Kokchetav massif: facts and models. Lithos 78, 307–318.

Dobretsov, N.L., Sobolev, N.V., Shatsky, V.S., Coleman, R., Ernst, W., 1995.Geotectonic evolution of diamondiferous paragneisses, Kokchetav complex, northern Kazakhstan: the geologic enigma of ultrahigh-pressure crustal rocks within a Paleozoic fold belt. Island Arc 4, 267–279.

Hermann, J., 2002. Experimental constraints on phase relations in subducted continental crust. Contrib. Mineral. Petrol. 143, 219–235.

Hermann, J., Rubatto, D., Korsakov, A., Shatsky, V.S., 2001. Multiple zircon inclusion growth during fast exhumation of diamondiferous, deeply subducted continental crust (Kokchetav massif, Kazakhstan). Contributions to Mineralogy and Petrology 141, 66–82.

Hermann, J., Spandler, C., Hack, A., Korsakov, A.V., 2006. Aqueous fluids and hydrous melts

98

in high-pressure and ultra-high pressure rocks: Implications for element transfer in subduction zones. Lithos 92, 399–417.

Korsakov, A.V., Hermann, J., 2006. Silicate and carbonate melt inclusions associated with diamonds in deeply subducted carbonate rocks. Earth and Planetary Science Letters 241, 104–118.

Korsakov, A.V., Theunissen, K., Kozmenko, O. A., Ovchinnikov, Y.I., 2006, Reaction textures in clinozoisite gneisses. Russian Geology and Geophysics 47, 497-510.

Mikhno, A.O., Korsakov, A.V., 2013. K2Oprograde zoning pattern in clinopyroxene from the Kokchetav diamond-grade metamorphic rocks: Missing part of metamorphic history and location of second critical endpoint for calc-silicate system. Gondwana Research 23, 920–930.

Mikhno, A.O., Schmidt, U., Korsakov, A.V., 2013. Origin of K-cymrite and kokchetavite in the polyphase mineral inclusions from Kokchetav

UHP calc-silicate rocks: Evidences from Confocal Raman Imaging. International Journal of Mineralogy 25, 807–816.

Schertl, H.P., Sobolev, N., 2013. The Kokchetav Massif, Kazakhstan: "Type locality" of diamond-bearing UHP metamorphic rocks. Journal of Asian Earth Science 63, 5–38.

Shushkanova A.V., Litvin Y. A., 2008. Experimental evidence for liquid immiscibility in the model systemCaCO3-Pyrope-Pyrrhotite at 7.0 GPa: The role of the carbonatite and sulfide melts in diamond genesis. The Canadian Mineralogist46, 991-1005.

Sobolev, N.V., P. Schertl, H., D. Neuser, R., 2006. Composition and paragenesis of garnets from ultrahigh-pressure calc-silicate metamorphic rocks of the Kokchetav massif (northern Kazakhstan). Russian Geology and Geophysics 47, 519–529.



Abstract Volume


Late Paleozoic intra-plate volcanism of the Tienshan-

Junggar region

Alexander Mikolaichuka, Inna Safonovab,c

aInstitute of Geology NAS, Erkindikave. 30, Bishkek, 720481, Kyrgyzstan bInstitute of Geology and Mineralogy SB RAS, Koptyugaave. 3, Novosibirsk, 630090, Russia cNovosibirsk State University, Pirogova St. 2, Novosibirsk, 630090, Russia

The Junggar–Tienshan Region is located in the western part of the Central Asian Orogenic Belt, the world’s largest accretionary orogen, which has evolved over more than 800 Ma as a result of multiple episodes of subduction-accretion and collision. The region includes many fields of Late Paleozoic to Paleogene intra-plate continental basalts formed in relation to mantle plume (e.g., Sobel and Arnaud, 2000; Simonov et al., 2008). The continental plume-related origin of the Meso-Cenozoic basaltic fields has been solidly proved based on detailed geological, geochronological, geochemical, and petrologic data (Simonov et al., 2014). The origin of the Late Paleozoic basalts remains debatable as different research teams consider them to be related to either an Andean-type continental margin or to a continental hotspot. The dilemma comes from the still disputable age of ocean closure and final continental collision in the region.

Late Paleozoic basalts occur within the Balkhash–Yili volcano-plutonic belt (Ryazantsev, 1999) or continental arc (Windley et al., 2007), geographically at the northern and southern mountain frames of the Yili basin, i.e., on the SW Junggar Ridge and northern Tienshan of south-east Kazakhstan, respectively. In places, the Late Paleozoic volcanogenic-sedimentary unit hosting the basalts overlies the weathered surface of Late Paleozoic red-coloured

sandstones. In general, the whole territory of N.Tienshan–W. Junggar is characterized by a large regional unconformity separating marine and active margin deposits of Early Carboniferous age and Late Carboniferous–Permian continental deposits (Skrinnik et al., 1994) suggesting eruption of basalts in a continental environment.

There are three geochemically different groups of Late Paleozoic basalts in SE Kazakhstan: (1) LREE-Ti-Nb enriched alkaline basalt (SWJunggar), (ii) Nb depleted basalts (south of the Junggar range) and (iii) HFSE depleted basalts (N. Tienshan). Group 1 alkaline basalts are geochemically close to plume-related OIB-type basalts of oceanic islands or intra-continental rifts. Groups 2 and 3 are characterized by lower HFSE (Ti, P, Nb, Zr, Y) and higher Al2O3. In general, they are compositionally similar to continentaland oceanic plateau basalts of the Siberian and Ontong-Java LIPs, respectively. On the other hand, they are geochemically similar to older (plateau-type) lavas of the Kerguelen hotspot track or to alkaline and subalkaline mafic lavas of Andean-type active margins and/or marginal seas. Thus, the Late Cretaceous of the Tienshan–Junggar region of SE Kazakhstan) resemble both oceanic and continental intraplate basalts related to mantle plumes (Hawaii, Central Mongolia) and lavas erupted at Andean-type active margins

100

or in passive margins/marginal seas or to those related to mantle plumes, but contaminated by crustal material resulting in HFSE depletion.

The Late Paleozoic lavas of SE Kazakhstan yielded Ar-Ar ages of 282 Ma (Group 1), 305.2±3.5 Ma (Group 2) and 311.9±3.7 (Group 3). The volcanic rocks obviously erupted in sub-aerial conditions, however the available geochronological and geochemical data do not allow us to reconstruct confidently their geodynamic setting. In terms of geochemistry they could have erupted in active margin, marginal sea or intra-plate settings. The Late Paleozoic orogens of the study area comprise the South Tienshan and Junggar–Balkhan orogenic belts. There are two models on their origin: on a convergent margin (island arc?) of the Kazakhstan consolidated continent (e.g., Yakubchuk, 2004; Biske and Seltmann, 2010) or in a post-orogenic continental environment (Lesik and Mikolaichuk, 2001; Simonov et al., 2014). The localities of basalts of different ages are separated from each other by local disconformities. We think that the Group 2 and 3 Late Carboniferous basalts, S. Junggar and N. Tienshan, respectively, were derived from crustally contaminated mantle sources. Group 1 basalts (Early Permian) could be related to the manifestation of the Tarim Plume active at ca. 290-274 Ma (Li et al., 2011).

Thus, we recognize two stages of continental/intra-plate magmatism manifested in the Tienshan–Junggar region. The Late Carboniferous magmatism (312-305 Ma) produced basaltic lavas geochemically similar to crustally contaminated varieties of the Siberian and Ontong-Java LIPs and Kerguelen hotspot. That was probably the first locally manifested stage of continental volcanism, in which lavas erupted over a still thin continental crust. The eruption of Early Permian volcanics coincide

with the time of the Tarim plume. The available geological data clearly

indicates that the volcanic rocks under consideration erupted after ocean closure. The northwestern circum-Junggar and South Tienshan orogens formed in place of the Junggar–Balkhash and Turkestan (or South Tienshan) Oceans, respectively, both were southern domains of the Paleo-Asian Ocean (Biske and Seltmann, 2010; Yang et al., 2014). The two oceans once separated the Kazakhstan and Siberian and the Kazakhstan and Tarim continental blocks, respectively, and probably closed in Late Carboniferous time (Lesik and Mikolaichuk, 2001; Xiao et al., 2011). More evidence for the Late Carboniferous ocean closure comes from (a) association of Late Carboniferous volcanics with coeval continental type deposits, (b) a large regional unconformity separating marine and active margin deposits of Early Carboniferous age and Late Carboniferous–Permian continental deposits, (c) the transverse position of SE Kazakhstan volcanic belts hosting the basalt localities in respect to the strike of the collisional belts, (d) the intra-plate geochemical features of Late Carboniferous–Permian granitoids in adjacent areas of the Tienshan (e.g., Konopelko et al., 2009), and (e) recent geochronological data from the adjacent areas in the Chinese Tienshan (Xiao et al., 2011). All this suggests that the Late Carboniferous volcanics of the Tienshan–Junggar region erupted in a continental setting, possibly over a thin continental crust locally covered by small and shallow ‘remnant’ seas, and the formation of the Early Permian basalts is related to a mantle plume.

Acknowledgements

Contribution to IGCP#592 ‘Continental construction in Central Asia’.

References

P BiskeYu.S., Seltmann R., 2010. Paleozoic

Tianshan as a transitional region between the Rheic and Urals–Turkestan oceans. Gondwana Research 17, 602–613.

Konopelko, D., Seltmann, R, Biske, G., Lepekhina, E., Sergeev, S., 2009.Possible source dichotomy of contemporaneous post-collisional barren I-type versus tin-bearing A-

type granites, lying on opposite sides of the

South Tien Shan suture. Ore Geology Reviews 35, 206–216

Lesik O.M., Mikolaichuk A.V., 2001. Deep structure of the Turkestan paleoocean suture (northeastern Fergana).Russian Geology and Geophysics 42, 1464-1470.

Li, Z., Chen, H., Song, B., Li, Y., Yang, S., Yu, X.,

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2011.Temporal evolution of the Permian large igneous province in Tarim Basin in north-western China. Journal of Asian Earth Sciences 42, 917–927.

Ryazantsev, A.V., 1999. The structures of the Middle Paleozoic active margin in Kazakhstan: lateral variability and migration. Doklady Earth Sciences 369, 659–663.

Simonov, V.A., Mikolaichuk, A.V., Rasskazov, S.V., Kovyazin, S.V., 2008. Cretaceous–Paleocene within-plate magmatism in Central Asia: data from the Tien Shan basalts. Russian Geology and Geophysics 49, 520–533.

Simonov V.A., Mikolaichuk A.V., Safonova I.Yu., Kotlyarov A.V., Kovyazin S.V., 2014. Late Paleozoic–Cenozoic intra-plate continental basaltic magmatism of the Tienshan–Junggar region in the SW Central Asian Orogenic Belt, Gondwana Research, http://dx.doi.org/10.1016/j.gr.2014.03.001.

Skrinnik, L.I., Grishina, T.S., Radchenko, M.I., 1994. Carboniferous stratigraphy and paleogeography of south-eastern Kazakhstan. Geology and Mineral Exploration in Kazakhstan 4, 9–18 (in Russian).

Sobel, E.R., Arnaud, N., 2000. Cretaceous–Paleocene basaltic rocks of the Tuyon basin, NW China and the Kirgiz Tian Shan: the trace of a small plume. Lithos 50, 191–215.

Windley, B.F., Alexeiev, D., Xiao, W., Kroner, A., Badarch, G., 2007. Tectonic models for accretion of the Central Asian Orogenic Belt. Journal of the Geological Society of London 164, 31–47.

Yakubchuk, A., 2004. Architecture and mineral deposit settings of the Altaid orogenic collage: a revised model. Journal of Asian Earth Sciences 23, 761–779.

Yang, G., Li, Y., Safonova, I., Yi, S., Tong, L., Seltmann, R., 2014. Early Carboniferous volcanic rocks of West Junggar in the western Central Asian Orogenic Belt: implications for a supra-subduction system. International Geology Review 56, 823-844.

Xiao, W.J., Windley, B.F., Allen, M.B., Han, C., 2013. Paleozoic multiple accretionary and collisional tectonics of the Chinese Tianshan orogenic collage. Gondwana Research23, 1316–1341.



Abstract Volume


The Vasilkovskoye stockwork gold deposit (North

Kazakhstan)

A. Miroshnikovaa, M. Rafailovichb, D. Titovc, R. Seltmannd aEast Kazakh State Technical University, Ust-Kamenogorsk, Kazakhstan bInstitute of Natural Resources YugGeo, Аlmaty, Каzakhstan cTOO «Kazzinc», Ust-Kamenogorsk, Kazakhstan dCERCAMS, Department of Earth Sciences, Natural History Museum, London, United Kingdom

The Vasilkovskoye deposit is a typical example of large gold deposits of the stockwork type. The deposit is located in North Kazakhstan, in the Kokshetau Massive - a large block of Precambrian metamorphic rocks, with anatexis and granitic magmatism in the Phanerozoic.

Geophysical criteria. The region of ore mineralization is located in a sub-latitudinal zone where the strength of the gravity field decreases, coinciding with a local uplift of the Conrad discontinuity and a depression in the Mohorovicic discontinuity. This is interpreted as being due to an increased thickness (24-26 km) of the granulite-basalt layer at depth. This lens coincides with maximum thickening of the crust and is believed to be the result of magmatic and metasomatic processes, involving interaction between rising fluids, basalt and andesite melts (Lyubetsky et al., 1985). The concentration of gold mineralization is controlled by hybrid intrusive rocks within the Dongulagashsky fault. Mineralogy and geochemistry

Mineralization is controlled by faults and fracture zones with NW, NE and latitudinal directions. A distinct zonal distribution of ore and gangue minerals, gold and accompanying ore elements is typical (Rafailovich, 2009). Paragenetic mineral associations of the ore stage are: early pyrite-pyrrhotite-marcasite-quartz; gold-pyrite-arsenopyrite-quartz (with pyrrhotite,

loellingite and chalcopyrite), gold-bismuth-pyrite, arsenopyrite-quartz (with molybdenite, cubanite, native Bi, bismuthinite, tetradymite, and mixed tennantite-tetrahedrite) and gold-polymetallic (with chalcopyrite, sphalerite, galena and tennantite); late quartz-carbonate-stibnite-tetrahedrite. The pyrite-pyrrhotite-marcasite-quartz association is predominantly developed at the intermediate and deep horizons; gold-pyrite-arsenopyrite-quartz and gold-bismuth-pyrite-arsenopyrite-quartz associations are found in the central part of mineralization; gold-polymetallic and quartz-carbonate-stibnite-tetrahedrite associations are typical of the upper horizons. Arsenopyrite is enriched in gold (up to a few hundreds g/t), Ag (5-50 g/t), Bi (up to 100-300 g/t), Pt (0.3-0.5 g/t), Cu, Pb, Zn, Co (up to 0.01-0.1%). Native gold is fine grained (up to 0.12 mm) and associated with the pyrite-arsenopyrite-quartz and the bismuthinite-pyrite-arsenopyrite-quartz assemblages. Non-metalliferous mineral veins form complicated relationships with the bodies of gold-bearing sulphide mineralization. Quartz veins of the ore stage (fine-grained dark-grey and grey quartz with sulphides and native gold) form the substance of the ore-bearing stockwork. Post-ore associations are calcite-quartz-sericite, fluorite-carbonate, quartz-tourmaline and carbonate-epidote-prehnite (Daukeev et al., 2004).

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Medium and high grades of gold are found in the central part of the ore-bearing stockworks, low grades occur in the periphery. Charts of gold distribution in the weathering crust and bedrocks are identical. Gold grades of 0.6-3.3 g/t are more widespread. Gold shows a positive correlation with Bi, As, Ag, Pb, Cu. Endogene aureoles of Bi define the spatial limit of the gold ore bodies. The outer boundary of the Ag, Pb, and Cu aureoles extends beyond the ore bodies for a few metres up to a few tens of metres (Abishev et al., 1972).

Summary. The Vasilkovskoye gold deposit is characterized by long-term ore-forming

processes from ore generation to ore deposition; the combined mantle – upper crustal magmatism and ore-bearing fluids; the distinct position in geophysical fields and tectonic dislocations; and the regular metasomatic, mineralogical and geochemical zoning. These characteristic features are pivotal for assessing the ore potential of the still unexplored flanks and deeper parts of the deposit and to detail the guidelines for focused prospecting of similar targets elsewhere. Acknowledgements

A contribution to IGCP-592.

References

Lyubetsky V.N., 1985. Deep criteria of localization of gold mineralization in Kazakhstan based on geophysical data. In: Experience of forecasting and evaluation of gold deposits in Kazakhstan. Alma-Ata, pp. 10-19.

Rafailovich M.S., 2009 Gold deposits of Kazakhstan: geology, metallogeny, exploration models. Almaty, 304 p.

Daukeev, S.Zn., Ushkenov, B.S., Bespaev, Kh.A., Miroshnichenko, L.A., Mazurov, A.K., Sayduakasov M.A., Eds., 2004. Atlas of mineral deposit models of the Republic of Kazakhstan, 141 p.

Abishev V.M., Bakhanova E.V., Zorin Yu.M., 1972. Geology, composition and geochemistry of the Vasilkovskoye gold deposit. In: Geology, geochemistry, and mineralogy of the gold districts and deposits of Kazakhstan. Alma-Ata, pp. 107-162.



Abstract Volume


Origins of the Supercontinent cycle

R. Damian Nancea and J. Brendan Murphyb

aDepartment of Geological Sciences, Ohio University, Athens, Ohio 45701, USA bDepartment of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia Canada, B2G

2W5

The supercontinent cycle, by which Earth history is seen as having been punctuated by the episodic assembly and breakup of supercontinents, has influenced the rock record more than any other geologic phenomena, and its recognition is arguably the most important advance in Earth Science since plate tectonics. It documents fundamental aspects of the planet’s interior dynamics and has charted the course of Earth’s tectonic, climatic and biogeochemical evolution for billions of years.

But while the widespread realization of the importance of supercontinents in Earth history is a relatively recent development, the supercontinent cycle was first proposed thirty years ago and episodicity in tectonic processes was recognized long before plate tectonics provided a potential explanation for its occurrence. With interest in the supercontinent cycle gaining momentum and the literature expanding rapidly, it is instructive to recall the historical context from which the concept developed.

Often overlooked in this exciting development is its progenitor, T.R. Worsley, who first proposed the existence of such a cycle in 1982 (EOS, 63 (45), 1104). Although advocacy of long-term episodicity in tectonic processes predates plate tectonics, Worsley was the first to link such episodicity to the cyclic assembly and breakup of supercontinents. Contending that such a cycle would be manifest

by peaks in collisional orogenesis lagged by rift-related mafic dike swarms, Worsley and his colleagues used available (Rb/Sr) data to argue that such episodes had punctuated Earth history at intervals of ~500 m.y. for at least the past 2.5 billion years. They predicted the existence of five supercontinents at ca. 0.6, 1.1, 1.7, 2.1 and 2.6 Ga (AGU Geophysical Monograph 32, 1985, 561-572), the dates of four of which correspond to the amalgamation of Gondwana, Rodinia, Columbia (Nuna) and Kenorland.

For the Phanerozoic, they modeled the cycle’s influence on sea level by estimating the independent effects of sea floor elevation on ocean basin volume and epeirogenic uplift on continental platform elevation, and showed that predicted water depths at the shelf break closely matched first-order Phanerozoic sea level change for a supercontinent cycle of ~440 Ma duration (Marine Geology, 1984, 58, 373-400). They also explored the cycle’s influence on tectonic trends, platform sedimentation, ice ages and global climate, major events in biogenesis, the marine stable isotope record and a wide range of biogeochemical signals (Paleoceanography, 1986, 1, 233-263). That many of these influences have been borne out by more recent research and most of the predicted supercontinents (now defined more precisely by U-Pb geochronology) have been named is a testament to this early work and a tribute to the concept’s originator.



Abstract Volume


Devonian-Carboniferous microfossils from the southern

Char Belt, east Kazakhstan

O.T. Obut and N.G. Izokh

Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia


The Char ophiolite or suture-shear zone of East Kazakhstan is located in the western Central-Asian orogenic belt and separates the Kazakhstan and Siberian cratonic blocks. The Char belt probably formed after closure of the Paleo-Asian Ocean and includes two types of volcanonogenic-sedimentary units, oceanic and suprasubduction (Safonova et al., 2012; Kurganskaya et al., 2014). The first type rocks are N-MORB and OIB basalts associated with sedimentary rocks of Oceanic Plate Stratigraphy, pelagic chert, hemipelagic siliceous-lime shale and mudstone, seamount carbonate breccia and carbonate cap, present in mélange (Safonova et al., 2012). Their age was constrained by Late Devonian–early Carboniferous radiolarians and conodonts (Iwata et al., 1997). So far, biostratigraphic geochronology has been the only way for determining the age of abundant volcanogeinc-sedimentary rocks. Recently, more microfossils have been obtained from the oceanic units of the Karabaev, Urumbaev and Verochar formations, which consist of basalt, tuff, tuffaceous sandstone, siliceous siltstone and mudstone, variably colored cherts and limestone. Radiolarians and conodonts were obtained from chert (red, greenish-grey, black) and limestones, respectively of the Karabaev and Urumbaev formations cropping out in the southern Char belt. The Verochar Formation consists of limestones intercalated with basalts, siliceous mudstones, cherts and tuffaceous sandstones. Radiolarians and conodonts were collected from

grey cherts in the western Char belt. The Upper Devonian radiolarian

assemblage recovered from the Urumbaev Fm.(Char dam) is diverse and includes Triloncheminax (Hinde), Tr. echinata Hinde, Tr. davidi (Hinde), Tr. sp., Astroentactiniastellata Nazarov, A. cf. paronae (Hinde), Borisella ? sp., Archocyrtium cf. typicum Cheng, Ar. sp., Tetraentactinia cf. barysphaera Foreman, Stygmosphaerostylus sp. 1, Stygmosphaerostylus sp. All identified species are typical of Upper Devonian sediments worldwide. Moreover Tetraentactinianbarysphaera and Archocyrtiumtypicum were described as typical Famennian species (e.g., Foreman, 1963; Cheng, 1986). Conodonts Palmatolepisrhomboidea Sannemann and Pal. sp. from the limestone are characteristic of Middle Famennian rhomboidea-Lower marginifera zones. We found diverse and relatively well preserved radiolarians and rare conodonts at two localities of the Karabaev Fm: southeast and northwest of Char town. The first assemblage contains Triloncheminax (Hinde), Tr. davidi (Hinde), Tr. echinata Hinde, Tr. sp., Stygmosphaerostylus sp., Tetraentactinia aff. barysphaera Foreman, and conodonts Palmatolepis sp., Polygnathus sp. Presence of Palmatolepis spp. and Tetraentactiniaaff. barysphaera suggest Upper Devonian (Famennian) age for the host strata. The second assemblage yielded Trilonche cf. vetusta Hinde, Tr. echinata Hinde, Tr. davidi


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(Hinde), Stygmosphaerostylus sp., Archocyrtium cf. reidelli Deflandre, Ar. cf. ormistoni Cheng, Ar. sp., Duplexia sp. Won, Helioentactinia sp. Polygnathus sp., Siphonodella cf. bella Kononova et Migdisova were recovered from among conodonts. Species Siphonodellabella was found from Tournaisian (Missisipian) duplicata Zone (Barskov et al., 1984) and recovered species of Archocyrtium are also characteristic of the Lower Carboniferous (Cheng, 1986).

Previously, the age of the Karabaev Formation was considered Frasnian–Famennian (?), and to occur beneath the Urumbaev Formation (Ermolov et al., 1980; Iwata et al., 1997). Our obtained microfossils record their

age as upper Devonian-lowermost Carboniferous. The Verochar Formation yielded typical Lower Carboniferous microfossils: Albaillella cf. paradoxa Deflandre, Albaillela sp., Polyentactinia sp. Conodonts Gnathodus cf. punctatus (Cooper). Radiolarians Albaillellaparadoxa are index-species for the same name zone known in the Tournaisian (Deflandre, 1952). The conodonts are characteristic for Siphonodellaisosticha–Upper S.crenulata - lower typicus zones and also confirms the Tournaisian age.

Acknowledgements Contribution to the IGCP 596 and 592

projects.

References

Barskov, I.S., Kononova, L.I., Migdisova, A.V., 1984. Conodonts from the Lower Tournaisian sediments of Podmoscovny Basin. In Menner V.V. (Eds.), Paleontological characteristic of the stratotype and reference Carboniferous sections of the Moscow Syncline. Moscow, MSU Press, pp. 3-33. [in Russian].

Deflandre, G. 1952. Albaillellanov.gen. Radiolaire fossile du Carbonifere Inferieur, Type d’uneligneaberrante Eteinte. C. R. Acad. Sci., Paris, 234, pp. 872-874.

Ermolov, P.V., Dobretsov, N.L., Polyansky, N.V., Klenina, N.L., Khomyakov, V.D., Kuzebny, V.S., Revyakin, P.S., Bortsov, V.D., 1981. Ophiolites of the Chara zone, in: Abdulin, A.A., Patalakha, E.I. (Eds.), Ophiolites. NaukaKazSSR, Alma-Ata, pp. 103–178 [in Russian].

Foreman, H.P., 1963.Upper Devonian Radiolaria from the Huron Member of the Ohio Shale. Micropaleontology 9 (3), 267–304.

Iwata, K., Obut, O.T., Buslov, M.M., 1997. Devonian and Lower Carboniferous Radiolaria from the Chara ophiolite belt, East Kazakhstan. News of Osaka Micropaleontologist 10, 27-32.

Kurganskaya E.V., SafonovaI.Yu., and Simonov V.A., 2014.Geochemistry and petrogenesis of suprasubduction volcanic complexes of the Char strike-slip zone, eastern Kazakhstan. Russian Geology and Geophysics 55, 69–84.

Nazarov, B.B., 1975. Radiolarians of the Lower–Middle Paleozoic of Kazakhstan: Methods of Study, Systematics, and Stratigraphic Significance. Transactions of the Geological Institute, Akademia Nauk SSSR 275, 1–202 [in Russian].

Safonova, I.Yu., Simonov, V.A., Kurganskaya, E.V., Obut, O.T., Romer, R.L., Seltmann, R., 2012. Late Paleozoic oceanic basalts hosted by the Char suture-shear zone, East Kazakhstan: Geological position, geochemistry, petrogenesis and tectonic setting. Journal of Asian Earth Sciences 49, 20–39.



Abstract Volume


Volcanic-related epithermal deposits in Kamchatka

volcanic arc (North-East of Pacific region)

Victor Okrugina, b and Elena Andreeva a,b,*

aKamchatka State University, Petropavlovsk-Kamchatky city, Russia bThe Institution of Volcanology and Seismology, Far East Branch of Russian Academy of Science,

Petropavlovsk-Kamchatsky 683006, Russia

In Kamchatka region the precious metal mineralization is scattered within the volcanic belts of Cretaceous–Quaternary age. The Central Kamchatka Oligocene–Quaternary volcanic belt stretches discontinuously for 800 km from the Koryak Mainland to down south of Kamchatka peninsula. It consists of large number of volcanoes hosting the Au mineralization. According to occurrence of the Au-bearing deposits, they were grouped into the North and the Central mining districts. The latter is known for the active mining operation and as a consequence, recently there has been reactivation of the exploration works on the economic potential prospects, which were first discovered between 1965-1980. Central Kamchatka mining district contains the open-space filling epithermal veins of Au-Ag-Te, Au-Ag and Au-Au-Base metal mineralization types, which are spatially associated with volcanic calderas of andesitic diorite, granodiorite-dacite and andesitic basalt in composition. Epithermal veins with typical crustiform and colloform banding textures basically consist of quartz, adularia with minor carbonate and clay components. Formation age of precious metal mineralization varies from Early Miocene to Early Pliocene.

This paper presents data on vein mineralogy and fluid inclusion studies on some gold-bearing quartz-carbonate-adularia veins of Central

Kamchatka mining district. Differences exist between age of formation, mineralogy, fluid inclusion temperatures, and values of oxygen and carbonate stable isotopes. Based on this a model of gold-silver mineralization at Central Kamchatka volcanic belt is suggested.

There are a number of economically significant and, also, scientifically attractive ore deposits, located in Central Kamchatka mining district. These are Aginskoe Au-Ag-Te, Baranevskoe Au-Ag, Zolotoe Au-Ag, and Kungurcevskoe Au-Ag deposits.

The Aginskoe deposit is a classic epithermal bonanza-type gold-hosted (Auav. 38 g/t) quartz-adularia vein system located within a volcanic caldera in the Central Kamchatka mining district. Abnormally high content of Te in the ores distinguishes the Aginskoe deposit from other precious metal deposits known in the district. Concentration of Te in ores ranges from 403 to 20,767 ppm. Underground mining targeted at the production of gold-silver ore started in 2006, and since then more than 10 t of Au has been produced. Gold content is highly variable and varies from 40 to 7,437 ppm.

The Aginskoe deposit is hosted by Miocene andesitic-basaltic rocks of the volcanic caldera at elevation of 1110 to 1430 masl in the Central Kamchatka volcanic belt. Unexposed veins extend up to 300 m in length with width varying from 5 to 30 m. Intrusion of gabbro-diorite

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emplaced in the vicinity of the epithermal veins yielded age of 7.40±0.20 Ma. Major minerals of hydrothermally altered host rocks are smectite, chlorite and kaolinite. Recently obtained K/Ar dating on vein adularia gives an age range of 7.4-6.9 Ma. The quartz-adularia-clays-carbonate crustiform banded veins host hypogene and supergene mineralization. There are six stages of vein development: barren massive quartz (stage I), ore mineralization occurring in quartz-adularia-micas crustiform gangue (Stage II), intensive brecciation (Stage III), post ore coarse amethyst (Stage IV), carbonate (Stage V) deposition and supergene mineralization (Stage IV). Gold is a main metallic mineral in ores presented in form of native gold, electrum and tellurides. Native gold is the most abundant mineral among Au-bearing phases. Compositionally native gold is homogeneous with Au content ranging from 89 to 92 at.%. Native gold was simultaneously deposited with Au-bearing tellurides as calaverite, krennerite and sylvanite prior to deposition of sphalerite, altaite and hessite. Au-bearing tellurides, however, has an importance to gold-enrichment in the supergene zone. Under intensive weathering calaverite, krennerite and sylvanite are transformed into new Au-rich phases. Some of these minerals have been previously classified as rare metallic alloys as bilibinskite, bessmartnovite and bogdanovite. This study shows that majority of Au-bearing secondary minerals are oxides and/or hydroxides containing Au, Te, Pb, Cu and Fe in different amounts. Although, primary tellurides are mostly decomposed, some of them still remain as relicts of the precursor phases such as calaverite, calaverite-petzite intergrowths, hessite or altaite in most cases. Preserved remnants of hypogene tellurides indicate the high ƒTe2 proximal to reaction calaverite-gold and relatively lower ƒs2 below pyrrhotite-pyrite reaction. Fluid inclusion data shows that hypogene mineralization has been formed from low-salinity fluids (0-2 wt.% NaCl eqv.) with temperatures of 250-280 °C. Fluid inclusions are liquid-rich and gaseous ones frequently coexist suggesting a boiling of the hydrothermal fluid. Abundant occurrence of adularia also supports the boiling phenomena. Quartz of Stage II and amethyst from the post-ore stage have values of δ18O -3.3 and -3.0-(-1.3) ‰. Stable isotope

studies on quartz and carbonate indicates a dominant meteoric component involved in the hydrothermal fluids.

The Baranevskoe deposit is located within the Balkhach super-volcanic caldera in the south-east of the Central Kamchatka mining district in approximately 40 km away from the Aginskoe Au-Ag-Te deposit. Two principally different ore types were defined at the Baranevskoe deposit: cupriferous and gold-silver-quartz-carbonate-adularia ores formed under different physicochemical conditions and the fluid source. Also single gold grains were found in cavities of alkaline metasomatites, hosting the cupriferous ores. Cupriferous ores have been formed prior to gold-silver from probably different fluids in source. This ore type consists of early pyrite-electrum-chalcopyrite-bornite-sphalerite and later tetrahedrite-tennantite assemblages. Bornite and chalcopyrite show micrographic texture caused by the relatively rapid cooling of the hydrothermal fluid. Electrum (Au 59-64 at%) is a very rare mineral in cupriferous ores, and tends to associate with pyrite and chalcopyrite. The tetrahedrite-tennantite series mineral is predominant, with tetrahedrite component showing heterogeneous distribution of Sb and As within tetrahedritess. Tetrahedrite probably resulted from the replacement of chalcopyrite and chalcopyrite-bornite. Tetrahedrite in cupriferous ores is characterized by a high Cu content and a high Zn/Fe ratio. Fluid inclusions show lower homogenization temperatures from 154 to 232 °C with salinity of 0.7-1.1 wt% NaCl equiv. Although liquid-rich inclusions were observed in co-existence with gaseous inclusions, boiling is not confirmed yet. Presence and dominance of tetrahedrite and the types of the alteration rocks suggest deposition of Cu-bearing ores from the low-temperature slightly alkaline fluids of high fS2 which relegates to the intermediate sulfidation state. The gold-silver ores occur as open-fracture filling veins, tiny stockworks and carbonate-rich ores. Both veins and stockwork are characterized by abundant occurrence of gold in association with sphalerite, galena, pyrite, chalcopyrite and trace amounts of tetrahedrite-tennantite. Carbonate-rich veins host moderate amounts of gold crystallized in interstices. The Au content in electrum varies broadly from 52 to 72 at%.

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Based on the fluid-inclusion studies, quartz-carbonate-adularia veins, stockwork and carbonate-rich ores are confirmed to be deposited from the hydrothermal fluids in shallow-depth with relatively lower temperatures of 190-280 °C and a salinity approximately 2 wt% NaCl equiv. Alteration rock styles support fluid of slightly acid-neutral to alkaline-neutral pH state. Stable isotope studies suggest a magmatic contribution in the hydrothermal fluids. Kungurcevskoe and Zolotoe deposits are located in the same area

with Baranevskoe deposit at a distance of about 12 km. Hydrothermal fluids of Zolotoe and Kungurcevskoe deposits are meteoric-water in origin based on the stable isotope studies. Both deposits are classified as LS type epithermal veins.

Acknowledgements This study was mainly financed by the

Strategic Development Program of Vitus Bering State University for 2012-2014.



Abstract Volume


Glimpses on the Late Palaeozoic floral diversity of

Tethyan region, Kashmir, India

Sundeep K. Panditaa and Deepa Agnihotrib

aDepartment of Geology, University of Jammu, Jammu-180006 (India) bBirbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow -226007(India) *Corresponding author e-mail: [email protected]

In India, the Carboniferous rocks are exposed in Kashmir and Spiti regions. The Carboniferous sediments of Kashmir are divided into Syringothyris Limestone, Fenestella Shale (Early Carboniferous) and Agglomeratic Slate (Late Carboniferous). Well preserved plant fossil assemblages have been reported from Syringothyris Limestone and Fenestella Shale formations of the Carboniferous period, exposed in Kotsu village, Wallarama spur, Manigam spur, Arbal and Gund villages. These fossils belong to different plant groups e.g. Lepidodendrales, Equisetales, Cordaitales and Filicales. The assemblage includes Archaeosigillaria sp., Lepidostrobus kashmirensis, Sublepidodendron quadrata, Aspidiaria, Pseudobumbudendron chaloneri, P. meyenii, P. fenestrata, Cyclostigma ungeri, Knorria-1, Knorria-2, Rhacopteris ovata, Triphyllopteris lescuriana, T. peruviana, Nothorhacopteris kellaybelenensis, Rhodea cf. subpetiolata, Palmatopteris cf. furcata, Archaeocalamites radiatus, Flabellofolium sp., Annularia sp., cf. Botrychiopsis plantiana, Cordaites sp. and decorticate axes. The Early Carboniferous flora of Kashmir shows resemblance with the flora of Argentina, China, U.S.S.R., Peru, Egypt, Pennsylvania, Virginia, Great Britain, Eastern Germany and North Africa due to the presence of Lepidodendropsis – Cyclostigma - Triphyllopteris. The Carboniferous flora of Kashmir shows resemblance with Thabo flora of Po Series in Spiti, Himachal Pradesh, India due to the

common occurrence of Rhacopteris and Rhodea. However, lycopsids which dominate the Early Carboniferous flora of Kashmir are not recorded from the Po Series of Spiti.

The Permian sediments of Kashmir are categorized into Nishatbagh Formation, Panjal Traps, Mamal Formation (Early Permian) and Zewan Formation (Late Permian). Plant fossils are only known from the Nishatbagh and Mamal formations. Floral assemblage of the Nishatbagh Formation is represented by Gangamopteris kashmirensis, Glossopteris longicaulis, G. nishatbaghensis, Psygmophyllum hollandii, Psygmophyllum sp., Cordaites sp. and Nummulospermum sp. The flora of Mamal Formation shows the admixing of northern and southern elements of the Permian Period and comprises various plant groups namely Equisetales, Sphenophyllales, Filicales, Glossopteridals, Cordaitales, Ginkgoales and Cycadales. The mega floral elements are represented by Sphenophyllum speciosum, S. thonii var. archangelskyii, S. thonii var. minor, S. thonii var. waltonii, Lobatannularia ensifolia, L. lingulata, Lobatannularia cf. sinensis, var. curvifolia, Glossopteris angustifolia, G. intermittens, Glossopteris cf. communis, Glossopteris cf. feistmantelii, Glossopteris cf. indica, Glossopteris taeniopteroides, G. taenoides, Glossopteris sp., Palaeovittaria kurzii, Vertebraia indica, Scutum leslium, S. pantii, Noeggerathiopsis hislopii, Ginkgophyllum haydenii, G. sahnii, Chiguites mamalensis,


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Cycadites meyenii, Vinaykumaria indica, Pecopteris mamalensis, P. nautiyalii, P. pahalgamensis, P. arborescens, Dizeugotheca ? falcata and Kashimopteris meyenii. The floral assemblages of Nishatbagh and Mamal formations are comparable with the flora of the Talchir, Karharbari and Barakar formations

(Early Permian) of Damodar, South Rewa, Mahanadi, Satpura, Godavari and Wardha basins of peninsular India. Zewan, the uppermost sequence of Permian Period in the Kashmir region contains well preserved faunal records. However, the sediments of Zewan Formation are devoid of plant fossils.

2014 Convention &11th International Conference on Godwana to Asia


Abstract Volume


The chaotic nature of mantle plume periodicity Andreas Prokoph

Speedstat, 19 Langstrom Crescent, Ottawa, Ontario, K1G5J5, Canada


Periodicities of ~140-170 Myr, ~60 Myr and ~30 Myr are evident in the Phanerozoic record of Large Igneous Province (LIP) eruptions. These eruptions are interpreted to be related to thermal convection in the Earth's mantle, forming upwelling events, the so-called ‘Mantle plumes’. The periodicities correlate well – and probably control at least partially – the long-term cyclic pattern observed in the ocean chemistry and biological diversity.

In the Early Cretaceous an ~30 Myr LIP periodicity appears for the first time. Using wavelet and fractal analysis on the observed data and a simple nonlinear model, it is demonstrated that this periodicity could have occurred as an

abrupt transition in the mantle convection from an ~60 Myr to an ~30 Myr cycle – a ‘bifurcation’. This change in periodicity is evident by utilizing wavelet analysis, but could not have been predicted from the older record. Consequently, considering the nonlinear nature of Earth's thermal convection much of the terrestrial-driven geological periodicities cannot be predicted by linear extrapolation. Besides the observed ‘frequency-doubling’ pattern, the large volcanic eruption pattern had been or may become highly chaotic in the Precambrian and in the future, respectively. This can explain fractally distributed clusters of LIP events in the Precambrian at a fractal dimension of d ~ 0.8.



Abstract Volume


Evolution of the continental crust; insights from the

zircon record

Nick M W Robertsa* and Christopher J Spencera

aNERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham, NG12 5GG, UK *Corresponding author e-mail: [email protected]

Zircon is a strong, resilient and refractory mineral that stores an abundance of isotopic and chemical information; thus, it provides the best deep-time record of Earth’s continental evolution. Zircon is abundant in most felsic rocks, can be precisely dated, and can fingerprint magmatic and metamorphic processes. It has been widely used to document the formation and evolution of continental crust during all parts of its history, from pluton- to global-scale. Some of the major contributions that zircon studies have had in our understanding of the formation of the continents will be reviewed here. These include the conditions of continent formation on early Earth, the onset of plate tectonics and subduction, the rate of crustal growth through time, and the role of preservation bias in the zircon record.

The Earth’s continental history is controlled by the secular evolution of the mantle, and cycles of mantle convection and overturn. Together these have led to the formation of the continental crust through time, and the periodic amalgamation of supercontinents; the zircon record reflects these processes. Global compilations of U-Pb crystallisation ages feature greater populations that correlate with the timing of supercontinent amalgamations, and both zircon-Hf and oxygen data feature greater amounts of crustal recycling during these periods. The way that orogens evolve and supercontinents form leaves an imprint on the zircon record, such that zircon-Hf data can be used to fingerprint these processes. The major supercontinents of Pangaea, Gondwana, Rodinia

and Columbia (Nuna), have all left their individual signatures in the zircon record. However, the extent to which the zircon record is representative remains inconclusive. Preferential preservation of crust during major collisional orogenesis remains a feasible process. Examples of possible preservational biases have been investigated using Rodinia-forming orogens; however, there is uncertainty concerning the representative nature of these Mesoproterozoic orogenies.

The zircon record has been used (and abused) many times to develop models of crustal growth rate. The role of preservation bias remains critical to the accuracy of these models. Two opposing end-member models are that 1) crustal growth increased during periods of supercontinent formation, and 2) that crustal growth increased during periods of supercontinent break-up. Arguably a third model should be that crustal growth is a continuous process with oscillations in growth rate only being an artefact of preservation. Our preferred interpretation of the zircon record, is that 1) peaks in U-Pb crystallisation ages are biased by collisional orogenesis, and 2) that trends in Hf isotope space reflect the balance between crustal growth and crustal destruction, with trends of increasing average εHf during supercontinent break-up suggesting enhanced growth during these periods. Furthermore, the zircon record is dominantly a proxy for felsic crustal growth, and crustal reworking. Crustal destruction, i.e. return of crust to the mantle, is the crucial variable that needs quantifying to truly model crustal growth


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rate through time. That being said, most evidence points to at least 50% of the current volume of continental crust existing by the end of the Archaean.

The Hadaean remains an enigmatic but crucial period in Earth’s history. There is abundant evidence that zircons in the Hadaean are derived from evolved felsic melts. Elevated oxygen and lithium isotope signatures suggest recycling of crust and water-rock interaction. Hf isotope signatures have been a matter of contention, but appear to indicate reworking of a mafic proto-crust that was extracted early in the Hadaean (>4.4 Ga). Thus, a geodynamic regime involving burial and internal reworking of crust is required. The record of magmatism, as indicated by the zircon age population from Jack Hills, is continuous and non-episodic. Such characteristics are compatible with a long-lived proto-crust that featured internal reworking and formation of evolved melts, but do not require any modern-day style plate tectonics.

The onset of plate tectonics has been a subject of great debate since this concept’s inception. Speculations for its onset range from the Hadaean to the Neoproterozoic; however, the Archaean remains the most popular timeframe. Marked changes in patterns of zircon-Hf data and zircon-Hf-based crustal growth curves have been reported around 3.0-3.2 Ga, but the relevance of these remains inconclusive. Arguably more striking, is a pattern of near-continuous juvenile crustal growth that starts around 3.9 Ga; we suggest this marks a change in geodynamics from a Hadaean protocrust to an Archaean regime. It is not clear from zircon data whether the latter represents true plate tectonics, or a more transitional regime with a strong vertical tectonic component. Crustal reworking, as recorded by zircon oxygen isotopes, increased after 2.5 Ga. This is interpreted as the onset of collisional orogenesis and the formation of supercontinents.

Fig. 1



Abstract Volume


Evaluation of juvenile versus recycled crust in the

Central Asian Orogenic Belt: importance of OPS, HP

belts and fossil arcs

I. Safonova

Institute of Geology and Mineralogy SB RAS, Novosibirsk, 630090, Russia *Corresponding author e-mail: [email protected]

The Central Asian Orogenic Belt (CAOB) is the world’s largest accretionary orogen, formed by multi-stage collisions of the Siberian, Kazakhstan, Tarim, and North China cratons. It is dominated by Pacific-type orogenic belts, which form over subduction zones, where oceanic lithosphere is submerged under active continental margins bringing together various fragments of oceanic (oceanic islands, plateaus and ridges) and continental (island arcs and microcontinents) crust to form accretionary complexes with LP-HT blueschist belts and which finally enlarges the continents. P-type belts are the most important sites of juvenile crust formation through TTG-type granitoid magmatism, i.e., calc-alkaline andesitic volcanism and M- and I-type granitoid magmatism (Maruyama et al., 1996). P-type orogens can be recognized by the presence of i) huge suprasubduction granitoid batholiths; ii) blueschists formed after mid-oceanic ridge basalt (MORB) and oceanic island/seamount/plateau basalt (OIB/OPB); iii) paired metamorphic belts; iv) sedimentary and magmatic units of Oceanic Plate Stratigraphy units (OPS), which are regular successions of MORB, pelagic chert, hemipelagic siliceous shale and mudstone, and trench fill turbidite; v) dominating mafic lavas, in particular, boninites

and OIBs, especially when the latter are capped by carbonates.

During the whole Phanerozoic the Siberian Craton grew by oceanic subduction lasting more than 600 Ma and accretion of numerous intra-oceanic arcs and Gondwana-derived microcontinents to its southern active margin (Safonova et al., 2011). The subduction ceased in the Late Paleozoic-Mesozoic by the closure of the Paleo-Asian Ocean and its Turkestan, Junggar and Mongol-Okhotsk branches and the collision of the Siberian Craton with the Kazakhstan, Tarim and North China blocks to become part of Laurasia. The CAOB hosts numerous localities of blueschists derived from MORB and OIB protoliths, accreted carbonate-capped OIBs and other OPS units, huge granitoid batholiths and boninites (Volkova and Sklyarov, 2007; Gordienko et al., 2007; Yarmolyuk et al., 2012; Safonova and Santosh, 2014). Consequently, the CAOB is dominated by P-type orogenic belts with subordinate smaller collision-type belts formed by local continent-microcontinent collisions. e.g., Kazakhstan and North Tianshan or Kazakhstan and Tarim. Thus, the Central Asian Orogenic Belt was a major supplier of juvenile crust in Asia during the Phanerozoic. The CAOB continental crust was overgrown by recycled

116

crust of microcontinents (MCs) and active margin granitoids and, according to different evaluations, contains 50 to 80% of recycled crust in spite of the dominantly P-type character of the CAOB (Kröner et al., 2014 and ref.s therein). Several areas of the central and SW CAOB are dominated by recycled crust, but host accreted OIB-type OPS, MORB/OIB derived blueschist belts and intra-oceanic arcs. This can be due to the destruction of juvenile crust formed at convergent margins, which have been proved for the Japanese islands (Yamamoto et al., 2009). As the present Western Pacific is a most probable analogue of the CAOB (Safonova et al., 2011),

up to 80% of the Neoproterozoic-Early Paleozoic juvenile crust of the CAOB could have been removed by tectonic erosion and then subducted to produce a large amount of recycled crust. The eroded/subducted TTG crust probably returned to the surface as supra-subduction granitoids with recycled isotope signatures or accumulated at the Mantle Transition Zone and served as a source of heat, which induced mantle upwelling, plumes and surface rifting (Safonova and Maruyama et al., 2014). Acknowledgements

Contribution to IGCP#592.

References

Gordienko, I.V., Filimonov, A.V., Minina, O.R., Gornova, M.A., Medvedev, A.Ya., Klimuk, V.S., Elbaev, A.L., Tomurtogoo, O., 2007. Dzhida island-arc system in the Paleoasian Ocean: structure and main stages of Vendian-Paleozoic geodynamic evolution. Russian Geology and Geophysics 48, 91-107.

Kröner, A., Kovach, V., Belousova, E., Hegner, E., Armstrong, R., Dolgopolova, A., Seltmann, R., Alexeiev, D.V., Hoffmann, J.E., Wong, J., M. Sun, Cai, K., Wang, T., Tong, Y., Wilde, S.A., Degtyarev, K.E., Rytsk, E., 2014. Reassessment of continental growth during the accretionary history of the Central Asian Orogenic Belt. Gondwana Research 25, 103-125.

Maruyama, S., Liou, J.G., Terbayashi, M., 1996.Bluschist and eclogites of the world, and their exhumation. International Geology Review 38, 485–594.

Safonova, I., Maruyama, S., 2014. Asia: a frontier of a future supercontinent Amasia.

International Geology Review. DOI: 10.1080/00206814.2014.915586.

Safonova, I., Seltmann, R., Kröner, A., Gladkochub, D., Schulmann, K., Xiao, W., Komiya, T., Sun, M., 2011. A new concept of continental construction in the Central Asian Orogenic Belt (compared to actualistic examples from the Western Pacific). Episodes 34, 186-194.

Safonova, I.Y., Santosh, M., 2014. Accretionary complexes in the Asia-Pacific region: Tracing archives of ocean plate stratigraphy and tracking mantle plumes. Gondwana Research 25, 126-158.

Volkova N.I., Sklyarov, E.V., 2007. High-Pressure Complexes of the Central Asian Fold Belt: Geological Setting, Geochemistry, and Geodynamic Implications. Russian Geology and Geophysics 48, 109–119.

Yamamoto, S., Senshu, H., Rino, S., Omori, S., Maruyama, S., 2009. Granite subduction: arc subduction, tectonic erosion and sediment subduction. Gondwana Research 15, 443–453.

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Abstract Volume


Partial melting process of mafic granulites from the

Neoproterozoic - Cambrian Lützow-Holm Complex,

East Antarctica: Evidence from crystallized melt

inclusions

Yohsuke Saitoha, Toshiaki Tsunogaea,b

aGraduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan bDepartment of Geology, University of Johannesburg, Auckland Park 2006, South Africa

1. Introduction Recently several authors reported the

occurrence of micro- to millimeter-scale crystallized melt inclusions (CMIs) and quenched glassy inclusions trapped in porphyroblastic minerals in granulites (e.g., Cesare et al., 2009; Hiroi et al., 2014). Such inclusions are thought to be a key not only to infer post-peak exhumation process but also to discuss the evolution of granulite terrains. Some authors concluded that the formation of CMIs requires rapid cooling and uplifting from the lower crust (e.g. Hiroi et al., 2014), whereas Cesare et al. (2009) argued that such glassy inclusions are products of slow cooling. The petrogenesis of such micro-scale inclusions are therefore now in debate. CMIs have so far been mostly reported from felsic and pelitic granulites probably because such quartzo-feldspathic rocks commonly experienced partial melting during prograde stage. In contrast, they are generally rare in mafic to ultramafic granulites, although minor dehydration melting of mafic to ultramafic granulites has also been reported (e.g. Garrido et al., 2006). In this study, we present new petrographic data of CMIs in mafic to ultramafic granulites from the Lützow-Holm Complex (LHC), East Antarctica, which is

characterized by the occurrence of various high-grade metamorphic rocks and magmatic intrusives formed during the Late Neoproterozoic to Early Cambrian collisional orogeny (e.g. Shiraishi et al., 1992). Particularly, we focused on pressure-temperature (P-T) conditions of partial melting and solidification of CMIs in mafic to ultramafic granulites to examine the lower crustal process of the orogenic belt.

2. Petrography and phase equilibria

modeling Previous petrological studies of the LHC

suggest an increase in the metamorphic grade from northeast (amphibolite facies) to southwest (granulite facies) (Hiroi et al., 1991). The examined mafic and ultramafic granulites occur as boudin or small blocks of several meters within psammitic and hornblende-biotite gneisses of the granulite-facies zone. Contacts between the boudins or blocks and the host gneisses are sharply defined, and the rocks show no obvious evidence of migmatization in outcrop and in hand-specimen scale. Based on detailed microscopic observations, we found CMIs bearing mafic and ultramafic granulites from four different exposures within the LHC. The

118

representative samples of mafic to ultramafic granulite are composed mainly of coarse-grained garnet, hornblende, orthopyroxene, clinopyroxene, plagioclase, and ilmenite. The garnet often contains inclusions of hornblende, biotite, ilmenite, rutile, plagioclase, and quartz as well as CMI. Fine-grained symplectites of orthopyroxene and plagioclase occur between the garnet and matrix clinopyroxene or hornblende, suggesting a post-peak decompression event. The CMIs consist of fine-grained quartz, orthopyroxene, biotite, K-feldspar, plagioclase, and ilmenite whose size varies from 1 to 50 μm. The size of CMI grains is up to 100 μm, and they show negative crystal shapes of the host garnet. Such fine-grained nature of each crystal and the shape of the CMIs might require quench processes of liquid during cooling stage of the inclusions (e.g. Hiroi et al., 2014). We subsequently calculated chemistry of CMI based on modal abundance and chemistry of the minerals for each CMI. The results are nearly equivalent to the compositions of andesitic to dacitic melt. Occurrence of hornblende and biotite within garnet in the rock suggests dehydration melting of the hydrous minerals and formation of andesitic to dacitic melt during prograde stage. Whole rock chemistry of the host mafic and ultramafic rock suggests depletion in Si and K if compared to basaltic rocks, which also supports partial melting and melt extraction. Phase equilibrium modeling in NCKFMASH system demonstrated that some mafic to ultramafic granulites experienced considerable amounts of melt loss (up to 15 wt.%) during partial melting, although the influence of partial melting can be neglected for other samples. Based on the integrated bulk compositions, we estimated peak P-T conditions of 850-870 °C and 13-14 kbar and clockwise P-T path for the rock. The peak conditions are comparable with but slightly higher than previous estimations of 800-950 °C and 7-12 kbar (Yoshimura et al., 2004) estimated by

garnet-two pyroxene-plagioclase-quartz geothermobarometers for the matrix assemblage. Our P-T ranges are also consistent with P-T estimates based on garnet-rutile-ilmenite-plagioclase assemblage in a kyanite-bearing pelitic granulite collected from the same locality (13-14 kbar at 850 °C).

3. Discussion This is the first detailed report of CMIs in

mafic to ultramafic granulites from the LHC. Occurrences of hornblende and biotite within garnet in CMI-bearing mafic to ultramafic granulite suggest that breakdown of these hydrous minerals might have caused dehydration melting during prograde stage. It has to be noted that prograde to peak conditions and mineral assemblages discussed in this study are similar to the results of López and Castro (2001) who demonstrated phase relations of melt and restitic phases (garnet bearing granulite) by experiments of amphibolite under fluid absent conditions. The results imply that dehydration melting could have taken place at the peak P-T conditions of our sample (12-14 kbar around 900 °C). According to their calculations, the maximum amount of melt production is 30 wt.% in the system, which is consistent with our phase equilibrium modeling that suggests 15 wt.% of melt could have been lost from the system, if we assume that our sample originated from amphibolite. Our results therefore suggest that partial melting and melt loss are common processes even in mafic to ultramafic granulites, and CMIs could preserve the composition of melt which has already been extracted from the system. We further conclude that a possible effect of melt loss should be taken into account for calculating the prograde to peak P-T conditions by phase equilibrium modeling if an examined rock contains CMI. Even if the rock shows no evidence of migmatization, micro-scale textures in garnet might preserve the traces of partial melting processes.

References

Garrido, C.J., Boudinier, J.L., Burg, J.P., Zeilinger, G., Hussain, S.S., Dawood, H., Chaudhary, M.N., Gervilla, F., 2006. Petrogenesis of mafic garnet granulite in the lower crust of the Kohistan paleo-arc complex (Northern

Pakistan): Implications for intra-crustal differentiation of island arcs and generation of continental crust. Journal of Petrology 47, 1873-1914.

Cesare, B., Ferreol, S., Salvioli, M.E., Pedron, D., Cacallo, A., 2009. “Nanogranite” and glassy inclusions: The anatectic melt in migmatites

119

and granulites. Geology 37, 627-630. Hiroi, Y., Shiraishi, K., Motoyoshi, Y., 1991. Late

Proterozoic paired metamorphic complexes in East Antarctica, with special reference to the tectonic significance of ultramafic rocks. In: Thomson, M.R.A., Crame, J.A., and Thomson, J.W. (eds) Geological Evolution of Antarctica, Cambridge University Press, Cambridge, 83-87.

Hiroi, Y., Yanagi, A., Kato, M., Kobayashi, T., Prame, B., Hokada, T., Satish, K, M., Ishikawa, M., Adachi, T., Osanai, Y., Motoyoshi, Y., Shiraishi, K., 2014. Supercooled melt inclusions in lower-crustal granulites as a consequence of rapid exhumation by channel flow. Gondwana Research 25, 226–234.

López, S., Castro, A., 2001. Determination of the fluid-absent solidus and supersolidus phase

relationships of MORB-derived amphibolites in the range 4-14 kbar. American Mineralogist 86, 1396-1403.

Shiraishi, K., Hiroi, Y., Ellis, D.J., Fanning, C.M., Motoyoshi, Y., Nakai, Y., 1992. The first report of a Cambrian orogenic belt in East Antarctica – An ion microprobe study of the Lützow-Holm Complex. In: M. Yoshida, K. Kaminuma, and K. Shiraishi (eds.) Recent Progress in Antarctic Earth Science. Terra, Tokyo, 67-73.

Yoshimura, Y., Motoyoshi, Y., Miyamoto, T., Grew, S. Edward., Carson, J. Christopher., Dunkley, J. Daniel., 2004. High-grade metamorphic rocks from Skallevikshalsen in the Lützow-Holm Complex, East Antarctica: metamorphic conditions and possibility of partial melting. Polar Geoscience 17, 57-87.



Abstract Volume


Hadean – Eoarchean crustal record from southern India

M. Santosh

School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, P.R.

China


In deviation to the popular concept that major crust production on the globe occurred during Neoarchean at ca. 2.7 Ga and 2.5 Ga, we recently reported evidence for continental growth during Mesoarchean from the Coorg Block in southern India (Santosh et al., 2013). An extended study surrounding the Coorg Block on a suite of metaigneous (granitoids, charnockite, amphibolite, felsic tuff and gabbro) and metasedimentary (quartz mica schist, fuchsite quartzite, ferruginous quartzite and BIF) rocks provides important clues on Neohadean and Eoarchean crustal record. Magmatic zircons in the metaigneous suite show multiple pulses of magmatism at ca. 3.5 Ga (granitoid), 3.2 Ga (charnockite), 2.7 Ga (metavolcanics), and 2.5-2.4 Ga (granitoids, gabbro, diorite and felsic tuff). The metasedimentary rocks accreted along the margins of the Coorg Block show multiple zircon population with mean 207Pb/206Pb ages at 3.4, 3.2, 3.1, 2.9, 2.7, 2.6, 2.5, 2.2, 2.0, and 1.3 Ga. Zircons in the 3.5 Ga metagranite show positive εHf(t) values ranging from 0.0 to 4.2 and Hf crustal model ages (TDM

C) of 3517 to 3658 Ma suggesting that the parent magma was derived from the Eoarchean juvenile sources. The zircons in the 3.2 Ga charnockite

display εHf(t) values in the range of -3.0 to 2.9 and Hf crustal model ages (TDM

C) of 3345 to 3699 Ma. The Neoarchean metagranites, amphibolite, felsic tuff and gabbro show both positive and negative εHf(t) values and a range of TDM

C values from 2904 to 3609 Ma suggesting magma derivation from Meso- to Eoarchean juvenile and reworked components. The εHf(t) values of detrital zircons from the metasedimentary suite also show both positive and negative values, suggesting multiple source rocks generated from juvenile components and reworked crust. The oldest TDM

C value (4031 Ma) is recorded by zircon grain in a ferruginous quartzite. The data suggest vestiges of Neohadean primordial continental crust with dominant crustal growth during Eoarchean and Mesoarchean, building the ancient continental nuclei in Peninsular India. These results have important implications in understanding the evolution of continental crust in the Early Earth. Acknowledgements

I thank our team members Q.Y. Yang, E. Shaji, M. Ram Mohan, T. Tsunogae and M. Satyanarayanan. This work contributes to the Talent Award to M. Santosh under 1000 Talents Plan from the Chinese Government.


References

Santosh, M., Yang, Q.Y., Shaji, E., Tsunogae, T., Ram Mohan, M., Satyanarayanan, M., 2013. An exotic Mesoarchean microcontinent: The Coorg Block, southern India. Gondwana Research, DOI: 10.1016/j.gr.2013.10.005.

http://www.sciencedirect.com/science/article/pii/S1342937X13003493

http://www.sciencedirect.com/science/article/pii/S1342937X13003493



Abstract Volume


Provenance of the Nambucca block (eastern Australia)

and implications for the early Permian eastern

Gondwanan margins

Uri Shaanana, Gideon Rosenbauma and Richard Wormaldb

aSchool of Earth Sciences, The University of Queensland, Brisbane 4072, Qld, Australia bSchool of Earth and Environmental Sciences, James Cook University, Townsville 4811, Qld, Australia

The late Paleozoic to early Mesozoic southern New England Orogen of eastern Australia exhibits an omega-shaped orogenic curvature (orocline). Oroclinal bending took place during the early to middle Permian and affected Devonian-Carboniferous subduction-related rocks. During the early Permian the geodynamics of the easternmost Gondwanan margin changed from contractional west-dipping subduction to backarc extension. The early Permian extension is evident in vast emplacement of early Permian granitoids and formation of widespread rift-related sedimentary basins (i.e. Sydney, Gunnedah and Bowen basins) that bound the New England Orogen to the west. An additional series of smaller early Permian basins is situated within the New England Orogen unconformably overlying the Devonian-Carboniferous forearc basins and accretionary complex. The Nambucca Block is the largest of these onboard early Permian basins, and is situated in the core of the oroclinal structure. We present new geochronological data from the Nambucca Block in an attempt to better understand its provenance, tectonic history and role in the formation of the oroclinal structure.

Detrital zircon geochronology (U/Pb ICP-MS ages) of six samples yielded 452 concordant

ages from across the block. The age spectra of detrital zircons consist of large components of Devonian-Carboniferous and Precambrian ages (57% and 32%, respectively), and additionally two early Permian clusters (4.9% combined). The youngest Permian zircon ages (285 Ma) provide a maximum age constraint for the deposition of the Nambucca sedimentary succession. These new data, in conjunction with recently obtained metamorphic ages from the Nambucca block, indicate that deposition must have occurred between 285 and 275 Ma. The Devonian-Carboniferous zircon ages are attributed to the New England magmatic arc, suggesting that material deposited in the Nambucca block primarily consisted of recycled detritus derived from the former (Devonian-Carboniferous) subduction complex. The presence of Precambrian ages indicates that the Nambucca basin also received older recycled detritus from the Australian continent. Based on these results, we suggest that the Nambucca block was deposited in an early Permian backarc environment. This geodynamic setting may have been directly linked to the formation of the orocline, which have likely been generated by slab rollback.



Abstract Volume


The Caucasian-Arabian segment of the Alpine-

Himalayan collisional belt: geology, volcanism and

neotectonics

Evgenii Sharkova, Vladimir Lebedeva, Inna Safonovab

aInstitute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS, Staromonetny

Per., 35, Moscow, 119017, Russia bInstitute of Geology and Mineralogy SB RAS, Koptyuga ave. 3, Novosibirsk, 630090, Russia

The Caucasian-Arabian belt is part of the huge Late Cenozoic Alpine-Himalayan orogenic belt formed by the collision of the Eurasian, Indian and Arabian continental plates. The belt consists of two domains: the EW-striking Greater Caucasus on the north and the Caucasian-Arabian Syntaxis (CAS) on the south. The CAS includes arc-like tectonic domains of the Lesser Caucasus and Eastern Anatolia and is characterized by a large NS-trending positive isostatic anomaly, which suggests the presence of mantle plume head underneath it (Sharkov et al., 2012). The Greater Caucasus constitutes the southern margin of the Eurasian plate; it is uplifted over the Main Caucasian Fault, which is part of the Kopetdag-Caucasian-Trans European megafault. The Alpine structure of the Greater Caucasus formed by NS horizontal compression generated by interaction of two plates: the Arabian indenter and the East European Craton (Trifonov et al., 2012). In the late Cenozoic, that plate interaction resulted in the transverse shortening of the CAS to 400 km, mainly at the expense of the territory south of the Main Caucasian Fault (Leonov, 2007). As the available seismic data do not reveal any subduction zone beneath the Caucasus (Sharkov et al., 2012), that shortening was due to the tectonic ‘diffluence’ of crustal material apart

from the Arabian indenter, in front of the East European Craton.

The CAS includes a Neogene-Quaternary volcanic belt, which is extended from Eastern Anatolia and to the Lesser Caucasus and farther to the Greater Caucasus (Sharkov et al., 2012; Keskin et al., 2013). The belt is dominated by two types of volcanic rocks: (1) large fields of plateau basalts possessing geochemical characteristics of intraplate (plume-related) rocks, and (2) calc-alkaline and shoshonite-latite volcanic rocks, which are petrologically and geochemically similar to those formed in a suprasubduction setting. More evidence for the plume origin of Type 1 basalts comes from geophysical data suggesting presence of a mantle plume head beneath the CAS. The origin of Type 2 volcanic rocks is unclear because no subduction zone has been identified in the region. We think that the calc-alkaline and shoshonite-latite magmas were derived by interaction of the mantle plume head with the crustal material at relatively shallow depths under strong high-pressure deformations. Such a deformation-related interaction led to the melting of both mantle and crustal materials and formation of ‘mixed mantle-crust’ magmas within the zone of collision (Lebedev et al., 2010; Chugaev et al., 2013). At present, the processes of deep mantle

124

dynamics are continuing to destroy the pre-Pliocene structure of the collision zone. However, the response of ‘shallow’ tectonics to the deep mantle processes is delayed.

Consequently, the mantle plumes are not manifested on the surface, e.g., in the form of extensional faulting or rifting, but that could be expected in future.

References

Chugaev, A.V., Chernyshev, I.V., Lebedev, V.A., Eremina, A.V., 2013. Lead isotope composition and origin of the Quaternary lavas of Elbrus Volcano, the Greater Caucasus: high-precision MC-ICP-MS data. Petrology 21, 16-27

Keskin, M., Oyan, V., Sharkov, E., Chugaev, A., Can Genk, S., Aysal, N., Duru, O., Kavak, O., 2013. Magmatism and geodynamics of Eastern Turkey. Geophysical Research Abstracts 15, 12874

Lebedev, V.A., Chernyshev, I.V., Chugaev, A.V., Gol'tsman, Yu.V., Bairova, E.D., 2010. Geochronology of Eruptions and Parental Magma Sources of Elbrus Volcano, the Greater Caucasus: K-Ar and Sr-Nd-Pb Isotope Data. Geochemistry International 48, 41-67.

Leonov, Yu.G., 2007. Cimmerian and late Alpine

tectonics of the Greater Caucasus. In: Leonov, Y.G., (Ed.), Alpine History of the Great Caucasus. GEOS, Moscow, pp. 317-340 (in Russian with English abstract).

Sharkov, E.V., Lebedev, V.A., Rodnikov, A.G., Chugaev, A.V., Sergeeva, N.A., Zabarinskaya, L.P., 2012. Features of Caucasian segment of the Alpine-Himalayan Convergence Zone:

Geological, volcanological, neotectonical, and geophysical dataю In: Sharkov, E.V. (Ed.), Tectonics, Recent advances. InTech, Rijekam pp. 37-52.

Trifonov, V.G., Bachmanov, D.M., Ivanova, T.P., 2012. Evolution of the Central Alpine-Himalayan Belt in the Late Cenozoic. Russian Geology and Geophysics 53, 221-233.

http://meetingorganizer.copernicus.org/EGU2013/EGU2013-7508.pdf



Abstract Volume


Gabbro-monzodiorite associations of Central Asian

Orogenic Belt: Age, petrogenesis, tectonic setting

Roman Shelepaeva,b, Vera Egorovaa,b, Andrey Izokha,b, Andrey Vishnevskya,b

a Institute of Geology and Mineralogy, Novosibirsk, Russia b Novosibirsk State University, Novosibirsk, Russia

The characteristic feature of many gabbro-monzodiorite associations worldwide is the presence of different geochemical types of mafic rocks differing in K2O and trace element content and K/Na ratio. In particular, the most common type is the association of gabbro, monzogabbro (gabbro with orthoclase and biotite) and monzonite (monzodiorites, monzonite and quartz monzonite). Phase field relationships are always observed between these geochemical types of rocks. The difference in composition is due either to variations in the composition of the protolith in the upper mantle, or varying degrees of contamination of mantle magma by crustal material or varying degrees of differentiation of primary mantle melts in intermediate magma chambers. In this regard, some gabbro-monzodiorite associations of Central Asian Orogenic Belt were investigated in terms of their isotopic composition. These gabbro-monzodiorite associations are located in different geodynamic setting and respond to different stages of magmatism: accretion, collision and rifting (Table 1).

The most-studied collisional gabbro-monzodiorite association in CAOB is Bashkymugur intrusion (BI) in Tuva, Eastern Siberia with age of 465±1.2 Ma. It consists of plagiowebsterite, gabbronorite, monzodiorite and quartz monzodiorite. Besides these rocks, porphyric monzogabbro forms small bodies in the western part of BI. The plagiowebsterite and the quartz monzodiorite of BI have similar εNd values of 4.2. and 4.17 respectively. These data

allow the suggestion that quartz monzodiorite was formed not due to contamination but as a result of fractional crystallization of basaltic magma in intermediate chambers. The porphyric monzogabbro shows εNd of 5.47 which is close to the εNd in depleted mantle, however these rocks have high content of K2O and trace elements. This discrepancy can be explained by the enrichment of the mantle source directly before melting. There are two models for the origin of gabbro-monzodiorite association of BI. The first hypothesis proposes that partial melting of fertile mantle resulted in the formation of basaltic melt slightly enriched in K and TR. Successive differentiation and fractional crystallization of basaltic melt led to the formation of gabbro and then monzodiorite of BI. In the framework of this hypothesis the porphyric monzogabbro was formed due to fractional crystallization of enriched basaltic melt which was a result of partial melting of metasomatized mantle. The second hypothesis suggests the simultaneous melting of slightly and highly metasomatized subduction-related mantle. The gabbro and monzodiorite of BI are the products of melting of slightly metasomatized mantle and the porphyric monzogabbro was formed from highly metasomatized mantle.

Examples of gabbro-monzodiorite association of accretion stage in CAOB are the Beger (BGI) and Bituut (BTI) intrusion which is located on the south of Lake Zone in Western Mongolia (Rudnev et al., 2009). The U-Pb

126

zircon concordant data from gabbros indicate their Late Cambrian age (BGI: 500.9±5.7 Ma, BTI: 504.4±4.4 Ma). This data allow relating the time of formation of these intrusions to the late stage of the development of island-arc systems, or to the beginning of accretion-collision processes. Study of isotope-geochemical Sm-Nd data for these intrusions showed that gabbro and quartz monzodiorites have very similar εNd: 6.84 for gabbro and 6.95 for quartz monzodiorites of BGI, and 7.12 and 7.87 respectively for the BTI.

Rift-related gabbro-monzodiorites associations in CAOB are Dzaraula (DUI) and Dzadgainur (DNI) intrusion in Central Mongolia (Yarmoluk et al., 2008). These intrusions consist of olivine gabbro, olivine and quartz monzodiorites and monzogabbro. Ar-Ar dating of biotite from monzogabbro shows 262.1±2.4 Ma and 248.3±2.4 Ma dates from monzodiorites of Dzadgainur intrusion (Poljakov et al., 2010). Thus, the formation of rift-related gabbro-monzodiorite associations is probably due to two-stage effect of Permian Khangai mantle plume. Isotope Sm-Nd data show that most

compositionally contrasting gabbro and monzodiorites of DUI and DNI have a similar εNd value. In particular εNd value of 0.62 for gabbro and 0.45 for monzodiorites of DUI and 2.24 and 1.46 respectively for the DNI. The monzogabbro of DUI shows εNd of 8.4 which is close to the εNd in DM, however these rocks have high content of K2O and trace elements. Thus, the same model can be suggested for the origin of DUI, as well as for BI. Model involves the simultaneous or sequentially melting of heterogeneous mantle.

In general, isotope Sm-Nd data of the studied gabbro-monzodiorites associations in CAOB of various tectonic stages indicate that the origin of low alkali gabbroids and middle alkali monzodiorites is the result of melting of slightly enriched mantle source. While monzogabbro in these associations were formed from different more enriched mantle source. Moreover, the melting of the second source was almost close in time to the first one. Acknowledgements

Work was supported by RFBR13-05-01132, 12-05-31121.

Intrusi

on Age and rock type εNd (T) and rock type Geological setting

BTI 504,4 ± 4,4 U-Pb,

gabbronorite

6.84, gabbronorite

6.95, monzodiorite Accretion stage [2]

Western Mongolia BGI

500,9 ± 5,7 U-Pb,

monzodiorite

7.12, gabbro

7.87, monzodiorite

BI 465±1,2, Ar-Ar

monzodiorite;

4.20, plagiowebsterite

4.17, monzodiorite

5.47, monzogabbro

Collisional stage

Probably, mantle plum-related

magmatism

Tuva, Eastern Siberia

DUI

269,2±4,1, U-Pb,

262,1±2,4, Ar-Ar

monzogabbro

0.62, gabbro

0.45, monzodiorite

8.4, monzogabbro Rift-related magmatism,

Western Mongolia

DNI 248.3±2.4 Ar-Ar

monzodiorite

2.24, gabbro

1.46, monzodiorite

Table 1. Isotope composition of gabbro-monzodiorite associations of CAOB

References

Poljakov G.V., Izokh A.E., Vishnevsky A.V., Travin A.V. 2010. New composition data and age of picrite and alkali basalt complexes of Northern Mongolia part of Central Asian Orogenic Belt. Doklady Earth Sciences 433, 1, 67-71.

Rudnev S.N., Izokh A.E., Kovach V.P., Shelepaev R.A., Terent’ev L.B. 2009. Age,

composition, source and tectonic setting of Early Palaeozoic granite of northern part of Lake Zone in Western Mongolia. Petrology 17, 5, 470-508.

127

Yarmoluk V.V. Kovalenko V.I., Kozakov I.K. 2008. Age of Khangai batholith and problem

of batholith forming in Central Asia. Doklady Earth Sciences 423, 1, 92–98.



Abstract Volume


Late Quaternary geyserites of the Ol’khon region

(northern part of the Central Asian Orogenic Belt):

geological setting, age and composition

T.M.Skovitinaa, E.V.Sklayrova, O.A.Sklyarovab, A. B.Kotovc, E.V.Tolmachevac,

S.D.Velikoslavinskyc

aInstitute of the Earth's Crust, Siberian Branch, Russian Academy of Sciences, Russia E-mail:

[email protected] bVinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences, Favorskogo str.,

2, Irkutsk, 664033, Russian Federation cInstitute of Precambrian Geology and Geochronology, Russian Academy of Sciences, Makarova emb.,

2, St. Petersburg, 199034, Russian Federation, E-mail: [email protected]

Geyserites are dense hyalite like rocks with very complex fabric, defined by combination of various textures and structures – spherulitic, globular, microlayered, fibrous, fluidal, loopy and brecciated. They are composed mostly of cryptocrystalline silicate substances, chalcedony, quartz and iron hydroxides. Some types of geyserites contain balanced tremolite with chalcedony matrix (Sklyarov et al., 2004) and highly crystalline graphite (Shumilova et al., 2011), which indicates high temperatures of the initial geyserite solutions.

Geyserites formed in subaerial conditions. The wide spread of the geyserites with brecciated structures indicates repeated (pulsing)

inflow of the initial solutions. 14C dating allowed the estimation of the

geyserite age as 23720±425 years (Sklyarov et al., 2007). Palynological analysis of the enclosing detrital sandy loams shows that their ages cannot be older then Late Neopleistocene (Sklyarov et al., 2004). The age of the travertines, associated with geyserites, belongs to the interval of 23720±425–19550±300 years (14C method; Sklyarov et al., 2007).

Acknowledgements Studies were conducted with support of

Russian Foundation for Basic Research (Project № 14–45–04091).


129

Fig. 1 Distribution of geyserites, travertines, and springs in the Ol’khon region: 1 - Siberian craton; 2 – Early Paleozoic collision suture; 3 – Cenozoic Primorsky fault escarp; 4 – Ol’khon Terrane (Early Paleozoic collision complex); 5 – Cenozoic inherited faults; 6 – geyserites (a) and travertines (b); 7 – springs.

References

Sklyarov, E.V., Fedorovskii, V.S., Kulagina, N.V., Sklyarova, O.A., Skovitina, T.M., 2004. The Late Quaternary «Geyser Valley» in the Western Flank of the Baikal Rift (Ol’khon Region). Doklady Earth Sciences 395A, 3, 324-327.

Sklyarov, E.V., Fedorovskii, V.S., Sklyarova, O.A., Skovitina, T.M., Danilova,

Yu.V., Orlova, L. A., Ukhova, N.N., 2007. Hydrothermal Activity in the Baikal Rift Zone: Recent Hot Springs and Deposits of Paleothermal Waters. Doklady Earth Sciences 412, 1, 101–105.

Shumilova, T.G., Danilova, Yu.V., Gorbunov, M.V., Isaenko, S.I., 2011. Natural Monocrystalline -Carbyne. Doklady Earth Sciences 436, 11, 152–154.



Abstract Volume


Petrology and phase equilibrium modeling of garnet-

bearing mafic granulites from the Highland complex, Sri

Lanka: implications for regional correlation of

Gondwana fragments

Yusuke Takamuraa, Toshiaki Tsunogaeb,c, M. Santoshd, Sanjeewa Malaviarachchie

aCollege of Geosciences, University of Tsukuba, Ibaraki 305-8572, Japan bFaculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan cDepartment of Geology, University of Johannesburg, Auckland Park 2006, South Africa dSchool of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road,

Beijing 100083, China eDepartment of Geology, Faculty of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka

Garnet-bearing high-pressure mafic granulites are a common lithology in many Gondwana fragments including southern India, Antarctica, and Sri Lanka, which correspond to parts of the East African - Antarctic Orogenic Belt formed by complex subduction-accretion-collision events related to the amalgamation of Gondwana supercontinent during Neoproterozoic to Early Cambrian (e.g., Santosh et al., 2009, 2012). These rocks occur as blocks or boudins of a few dm to several km in size elongated parallel to the foliation of matrix ortho- and paragneisses. It is generally known that mineral assemblages in mafic granulites vary significantly depending on metamorphic pressure conditions as well as temperature, therefore the lithology has been regarded as an indicator of maximum pressure condition that the rock underwent. In this study we compute the prograde and peak metamorphic conditions of mafic granulites from the Highland Complex in Sri Lanka, and compare the results with those from similar Neoproterozoic to Early Cambrian

terranes in southern India (Palghat-Cauvery Suture Zone) and East Antarctica (Lützow-Holm Complex) for regional correlation of P-T conditions within the Gondwana Orogeny.

The mafic granulites occur as lenses of about a few m in length within metasediments of the Highland Complex. Mineral assemblages of the rocks are garnet + clinopyroxene + orthopyroxene + ilmenite + hornblende + plagioclase (type 1) and garnet + plagioclase + clinopyroxene + orthopyroxene + quartz + ilmenite (type 2). Type 1 is composed mainly of coarse-grained subidioblastic garnet and orthopyroxene. Type 2 shows decompression texture defined by orthopyroxene + plagioclase symplectite around garnet, which was probably formed by the reaction: garnet + quartz => orthopyroxene + plagioclase. Similar textures suggesting clockwise P-T evolution have been reported from mafic granulites in the Palghat-Cauvery Suture Zone in South India (e.g., Nishimiya et al., 2008; Saitoh et al., 2011a) and the Lützow-Holm Complex in East Antarctica

131

(Saitoh et al., 2011b). Based on geochemical data, protoliths of type 1 and 2 rocks are inferred to have been derived from MORB-like and island-arc basaltic sources, respectively. P-T conditions inferred for type-1 mafic granulites based on pseudosection analysis in NCFMASHTO system are 900-950 °C and 10.5-11.0 kbar. Although the conditions are significantly lower than the peak metamorphic condition inferred from mafic and pelitic granulites from the Highland Complex (>18 kbar, >1000 °C; Osanai et al., 2006), they are

consistent with the conditions reported for garnet-bearing mafic granulites from the Palghat-Cauvery Suture Zone and the Lützow-Holm Complex (e.g., Saitoh et al., 2011a,b; Koizumi et al., 2014). Similar occurrences and P-T evolution of mafic granulite bodies in several Gondwana fragments are comparable with the present model that the India - Sri Lanka - Antarctica region underwent high-P and ultrahigh-T metamorphism during the final stages of collision and incorporation into the Gondwana assembly.

References

Koizumi, T., Tsunogae, T., Santosh, M., Tsutsumi, Y., Chetty, T.R.K., Saitoh, Y., 2014. Petrology and zircon U-Pb geochronology of metagabbros from a mafic-ultramafic suite at Aniyapuram: Neoarchean to Early Paleoproterozoic convergent margin magmatism and Middle Neoproterozoic high-grade metamorphism in southern India. Journal of Asian Earth Sciences, doi: 10.1016/j.jseaes.2014.04.013.

Nishimiya, Y., Tsunogae, T., Santosh, M., 2008. Petrology and fluid inclusions of garnet-clinopyroxene rocks from Paramati in the Palghat-Cauvery Shear Zone System, southern India. Journal of Mineralogical and Petrological Sciences 103, 354-360.

Osanai, Y., Sajeev, K., Owada, M., Kehelpannala, K.V.W., Prame, W.K.B., Nakano, N., Jayatileke, S., 2006. Metamorphic evolution of high-pressure and ultrahigh-temperature granulites from the Highland Complex, Sri Lanka. Journal of Asian Earth Sciences 28, 20-37.

Saitoh, Y., Tsunogae, T., Santosh, M.,

Chetty, T.R.K., Horie, K., 2011a. Neoarchean high-pressure metamorphism from the northern margin of the Palghat-Cauvery Suture Zone, southern India: petrology and zircon SHRIMP geochronology. Journal of Asian Earth Sciences 42, 268-28.

Saitoh, Y., Tsunogae, T., Santosh, M., Chetty, T.R.K., 2011b. High-pressure mafic granulites from the Lützow-Holm Complex (Antarctica) and the Palghat-Cauvery Suture Zone (Southern India): implication for the extension of the Gondwana suture zone. International Association for Gondwana Research Conference Series 12, 66-67.

Santosh, M., Maruyama, S., Sato, K., 2009. Anatomy of a Cambrian suture in Gondwana: Pacific-type orogeny in southern India? Gondwana Research 16, 321-341.

Santosh, M., Xiao, W.J., Tsunogae, T., Chetty, T.R.K., Yellappa, T., 2012. The Neoproterozoic subduction complex in southern India: SIMS zircon U-Pb ages and implications for Gondwana assembly. Precambrian Research 192-195, 190-208.



Abstract Volume


Zircon U-Pb geochronology of the Songshugou ophiolite:

new constraints and implications for Paleozoic tectonic

evolution of the Qinling orogenic belt

Li Tanga, M. Santosha, Yunpeng Dongb

aSchool of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road,

Beijing 100083, China;

bState Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an

710069, China

The Qinling orogenic belt (QOB) in central China extends from east to west for nearly 2500 km, and was constructed by the subduction and collision of the North China Craton with the South China Craton (Fig.1B). Multiple stages of rifting and convergence between the two cratonic blocks resulted in the complex geologic framework of the QOB (Dong et al., 2008). The belt is divided into the North Qinling terrane and the South Qinling terrane by the Paleozoic Shangdan suture zone (Meng and Zhang, 2000).

The Songshugou ophiolite is located at the northern domain of the Shangdan suture zone, and is considered to represent remnants of a former ocean basin (Dong et al., 2008). The age and character of the Songshugou ophiolite are of crucial importance for understanding the Proterozoic tectonic evolution of the QOB.

In this study, we analyzed the zircon grains from a garnet amphibolite. The grains were colorless and translucent and mostly anhedral or subhedral with length varying from 50 to 200 μm and aspect ratios ranging from 2:1 to 1:1. In

cathodoluminescence (CL) images, most of the grains are homogeneous and gray, with few grains showing weak core-rim texture with a small bright core. A total of 18 spots were analyzed from 18 zircon grains, and the results show very low Th (0.01-0.31 ppm) and U (1.44-21.33 ppm) contents and Th/U ratios ranging from 0.002-0.062. The zircon trace element patterns show enriched HREE and no obvious negative Eu anomaly, suggesting that most of the grains are of metamorphic origin.

All of the analyzed spots form a coherent group and yield, within analytical error, a weighted mean 206Pb/238U age of 515±12 Ma (MSWD = 1.9) (Fig.1). This age is similar to the ca. 500 Ma ages reported for the (ultra)high pressure metamorphism in north Qinling (Yang et al., 2002; Cheng et al., 2004). We suggest that the age reported in this study from the garnet amphibolite in the Songshugou ophiolite represents the timing of ocean closure and collision during Paleozoic in north Qinling.

133

Fig. 1 U-Pb concordia plot and age data histogram with probability curves for garnet amphibolite (13QL-24) from Songshugou ophiolite.

References

Cheng, D.L., Liu, L., Sun, Y., Zhang, A.D., Liu, X.M., Luo, J.H., 2004. LA-ICP-MS zircon U-Pb dating for high pressure basic granulite from North Qinling and its geological significance. Chinese Science Bulletin 49, 2296-2304.

Dong, Y.P., Zhou, M.F., Zhang, G.W., Zhou, D.W., Liu, L., Zhang, Q., 2008. The Grenvillian Songshugou ophiolite in the Qinling Mountains, Central China: Implications for the tectonic evolution of the Qinling orogenic belt. Journal of Asian Earth

Sciences 32, 325–335. Meng, Q.R., Zhang, G.W., 1999. Timing of

collision of the North and South China blocks: controversy and reconciliation. Geology 27, 123–126.

Yang, J.S., Xu, Z.Q., Pei, X.Z., Shi, R.D., Wu,C.L., Zhang, J.X., Li, H.B., Meng, F.C., Rong, H., 2002. Discovery of diamond in North Qinling: evidence for a giant UHPM belt across Central China and recognition of Paleozoic and Mesozoic dual deep subduction between North China and Yangtze plates. Acta Geologica Sinica 76, 484-495 (in Chinese

with English abstract).



Abstract Volume


Geochronology and geochemistry of the Damiao

gabbro–anorthosite suite in the North China Craton:

petrogenetic and geodynamic implications

Xueming Teng*, M. Santosh

School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road,


The North China Craton (NCC) is the largest and oldest cratonic nucleus in China. After a prolonged crustal evolution history during Neoarchean and the assembly of micro-blocks, the NCC finally evolved into a stable craton through the collision between the Eastern and Western Blocks in the late Paleoproterozoic ca. 1.85-1.80 Ga (Santosh, 2010; Zhai and Santosh, 2011; Santosh et al., 2013; Zhao and Zhai, 2013). The Damiao igneous complex near Chengde is a composite suite of gabbro-anorthosite that was emplaced during the post-collisional stage following the amalgamation of the Eastern and Western Blocks within the NCC (Zhang et al., 2007). Based on field investigation and petrologic studies, we identified the following lithologies in the suite: anorthosite, leuconorite, gabbroic anorthosite, norite, gabbronorite, noritic gabbro, ferrodiorite, Fe-Ti-(P)-rich gabbro and Fe-Ti ore. We present zircon LA-ICP-MS U-Pb age data on noritic gabbro, norite, leuconorite, gabbronorite, and gabbroic anorthosite, and the results yield weighted mean 207Pb/206Pb ages of 1731±22 Ma (MSWD = 0.26), 1667±22 Ma (MSWD = 0.79), 1746±24 Ma (MSWD = 0.16), 1725±24 Ma (MSWD = 0.19), and 1728±24 Ma (MSWD = 0.31), respectively. Our data show a relatively long-lived

crystallization process within the magma chamber. All of the different lithologies have similar rare earth element patterns and epsilon Hf ranging from −10.2 to −3.0, indicating their co-magmatic nature and derivation from the same magma chamber through differentiation. Polybaric crystallization is suggested by high pressure (11-13 kb) crystallization of megacrysts in the magma chamber. The ascent of the magma along zones of weakness led the pressure decrease followed by low pressure crystallization. During the ascent, the unfractionated magma most likely generated dykes along rift zones as proposed by Zhang et al. (2007). These dykes are characterized by moderate SiO2 (47.01–48.69 wt. %), high Al2O3 (12.13–20.45. %), high Fe2O3

t+TiO2 (9.89–15.85 wt. %), low Cr (9.33–495ppm) and Ni (8.62–182ppm), identical to the geochemical features of high alumina gabbro from the Harp Lake complex (Emslie, 1980) and Laramie anorthosite complex (Mitchell et al., 1995). These dykes thus correspond to high alumina basalt and represent the parental magma of the suite. The Fe-Ti-(P)-rich gabbro and Fe-Ti ore might represent the cumulate phases within the magma chamber after the removal of relatively light minerals by buoyancy through gravitation.


135

The high initial pressure and corresponding depth of 50–60 km are consistent with upper mantle origin or melting of a thickened crust resulting from the collision between the two major crustal blocks (Simmons and Hanson, 1978). Their zircon epsilon Hf compositions plot along the evolution line of the 2.5–3.0 Ga Neoarchean rocks in the NCC, suggesting that the magma derivation involved components from the ancient lower crust. High degree of melting (>75%) and high pressure are needed to produce parental high alumina basaltic magma from the lower crust (Duchesne et al., 1999; Longhi et al.,1999). These dykes exhibit tholeiitic nature and depletion of Nb, Ta and are relatively rich in Th, U, K, which are consistent with rift affinity and continental arc signature,

respectively. In summary, we propose that the magma source involved ancient crust that was thickened by the collision of the Eastern and Western blocks of the NCC, and the initial magma was formed at depths of about 50–60 km, where the pressure is high enough to cause the initial high pressure crystallization. The heat for the large extent of melting might have come from upwelling asthenosphere triggered by the slab break-off following the collision between the Eastern and Western blocks. The deep seated magma chamber under the thickened continental arc was then injected to mid-crustal depth along a rift zone generated during the extensional phase and underwent low pressure crystallization and differentiation to form the Damiao suite.

References

Duchesne, J.C., Liegeois, J.P., Vander Auwera, J., Longhi, J., 1999. The crustal tongue melting model and the origin of massive anorthosites. Terra Nova 11, 100–105.

Emslie R F, Geological Survey of Canada. Geology and petrology of the Harp Lake Complex, central Labrador: an example of Elsonian magmatism. Geological Survey of Canada, 1980.

Longhi, J., Vander Auwera, J., Fram, M.S., Duchesne, J.C., 1999.Some phase equilibrium constraints on the origin of Proterozoic(massif) anorthosites and related rocks. J. Pet. 40 (2), 339– 362.

Mitchell J N, Scoates J S, Frost C D. High-Al gabbros in the Laramie Anorthosite Complex, Wyoming: implications for the composition of melts parental to Proterozoic anorthosite. Contributions to Mineralogy and Petrology, 1995, 119(2-3): 166-180.

Simmons E C, Hanson G N. Geochemistry and origin of massif-type anorthosites. Contributions to Mineralogy and Petrology,

1978, 66(2): 119-135. Santosh, M., 2010.Assembling North China

Craton within the Columbia supercontinent: The role of double-sided subduction. Precambrian

Research, 178, 149-167. Santosh, M., Liu, D., Shi, Y., Liu, S.J., 2013.

Paleoproterozoic accretionary orogenesis in the North China Craton: A SHRIMP zircon study. Gondwana Research 227, 29-54.

Zhai, M.G., Santosh, M., 2011. The early Precambrian odyssey of the North China Craton: A synoptic overview. Gondwana Research 20, 6-25.

Zhang, S.H., Liu, S.W., Zhao, Y., Yang, J.H., Song, B., Liu, X.M., 2007. The 1.75 – 1.68 Ga anorthosite-mangerite-alkali granitoid-rapakivi granite suite from the northern North China Craton: Magmatism related to a Paleoproterozoic orogen. Precambrian Research 155, 287-312.

Zhao, G.C., Zhai, M.G., 2013. Lithotectonic elements of Precambrian basement in the North China Craton: Review and tectonic implications. Gondwana Research 23, 1207-1240.



Abstract Volume


Permo-Triassic palaeofloristics of Allan Hills, central Transantarctic Mountains, SVL, Antarctica: Palaeoecology and phytogeography

Rajni Tewaria and Sankar Chatterjeeb aBirbal Sahni Institute of Palaeobotany 53, University Road, Lucknow -226007, India

Email:[email protected] bTexas Tech University, Lubbock, TX 79401, USA

The Beacon Supergroup in the Allan Hills is divided into two units, the lower Victoria Group represented by the Gondwana system consisting mainly of fluvial siliciclastics and the upper Ferrar Group of volcanic origin. The Victoria Group consists of Permian glacial beds at the base, the Metschel Tillite, which is overlain successively by the Weller Coal Measures of Permian age, Feather Conglomerate and Lashly Formation of Triassic age. The Permo-Triassic sequences represent post-glacial flat-lying fluvial strata of shales and sandstones, intercalated with sparse coal seams. Plant megafossils are abundant throughout much of the Victoria Group and give a broad indication of the age of the sediments. The Weller Formation is represented by coal-bearing horizons and consists of three members, A, B and C based on different lithologies. Fossil plants belonging to the Glossopteris flora are recorded from the Member C. The Weller Formation is overlain by the massive Feather Formation which is devoid of coal and megafossils. The Lashly Formation gradationally overlies the Feather Conglomerate and is composed of four members, A, B, C and D. Member C contains a thin bed (~5 cm thick) of silicic tuff interlayered with Dicroidium-bearing shale indicating a proximal source of volcanism. The Triassic strata are overlain by the Ferrar Group comprising the Early Jurassic

Mawson Formation and the Late Jurassic Ferrar Formation.

Investigations on plant megafossils from the Permian and Triassic Wellar and Lashly formations, respectively, have revealed presence of rich and diversified Glossopteris and Dicroidium floras. The Glossopteris flora includes the plant taxa of the orders Calamitales and Equisetales of pteridophytes, and Glossopteridales, Cordaitales and Ginkgoales of gymnosperms comprising branched calamitalean axis, branched and unbranched equisetalean axes, nine species of the genus Gangamopteris, thirty five species of the genus Glossopteris, five scale leaves, Noeggerathiopsis hislopii and Ginkgoites sp. Diversity and abundance of the Weller flora may be attributed to the conducive warm, temperate and humid climatic conditions. Further, the assemblage is globally comparable with the Permian floras of other Gondwana countries. A strong affinity with the Late Permian Glossopteris flora of India is indicated suggesting that India and Antarctica were part of a single phytogeographic unit during this time. Besides, presence of nine species of the genus Gangamopteris – considered a marker taxon of the Early Permian horizons of Gondwana, from the Weller Formation, suggests its continuation in the Late Permian.

The Dicroidium flora is heterogenous and

137

includes pteridophytes and gymnosperms represented by the orders Equisetales, Corystospermales, Peltaspermales and Pinales. The plant taxa Calamites aliwalensis, Neocalamites carreri and Neocalamites sp., nodal diaphragms and calamitalean axes represent the sphenopsids. The flora is dominated by the Corystospermales, which is represented by 14 species of the genus Dicroidium, Pteruchus sp., Matatiella sp. and a seed fern cupule. Peltaspermales comprise male and female reproductive structures namely, Townrovia polaris and Matatiella dejerseyi, respectively. Pinales are represented by Heidiphyllum elongatum foliage and a cone. The megafossil assemblage is similar to those recorded from the Triassic of different

Gondwana continents namely, Argentina, New Zealand, South Africa, Australia, India and other parts of Antarctica. Globally warm conditions have been interpreted for the Triassic period due to volcanic activity especially linked to continental flood volcanism, high CO2 concentrations and methane hydrate destabilization. Earlier records of some massive fluvially transported woods, paleosols and tree ring analysis of the Dicroidium along with the rich plant fossil assemblage recorded from the Lashly Formation of Allan Hills suggest that the climate in Antarctica during the Triassic was warm and humid enough to support substantial forests.



Abstract Volume


Cu-Ni-PGE deposits of east Siberia hosted by Neoproterozoic mafic-ultramafic complexes

N.D.Tolstykha, G.V.Polyakova, A.E.Izokha, M.Yu Podlipskya, A.S.Mekhonoshinb,

D.A.Orsoevc , T.B.Kolotilinab

aInstitute of Geology and Mineralogy of Siberian Branch of the Russian Academy of Sciences

(SB RAS), Novosibirsk, Russia bInstitute of Geochemistry SB RAS, Irkutsk, Russia cInstitute of Geology SB RAS, Ulan-Ude, Russia

Magmatism and metallogeny of Large Igneous Provinces (LIP) including mineral deposits formed in continental margin settings have been a focus of recent studies of many research teams. The Alhadyr terrane at the southern margin of the Siberian Craton is part of the East Siberian metallogenic province (ESMP) and hosts mafic-ultramafic (MUM) intrusions with Cu-Ni-PGE mineralization. The ESMP includes MUM intrusions of the Kan and Biryusa blocks and the Yoko-Dovyren MUM pluton of the Baikal-Patom zone (Fig. 1).

There are three ore clusters of Cu-Ni-PGE-bearing dunite-peridotite-pyroxenite intrusions in the Biryusa block (Mekhonoshin and Kolotilina, 2009): Biryusa-Tagul, Udа-Biryusa and Barbitay. The lenticular intrusions are dominated by dunite and wehrlites with subordinate peridotite and olivine gabbro containing disseminated to massive sulphide ores. The intrusions have been strongly deformed and metamorphosed. The Biryusa and Yoko-Dovyren intrusions are compositionally similar: negatively correlated Al2O3 and MgO suggesting fractionation of olivine, LREE-enriched rare-earth element patterns, positive distribution of PGE and high concentrations of refractory PGE (Ir, Os).

The ESMP intrusions are dominated by

pyrrhotite–pentlandite ores, in which the concentrations of Ni are higher than those of Cu. The ratio of Fe/Ni in pentlandite, which is major ore mineral, reaches 1.7 (Alhadyr terrane). All dunite–peridotite–pyroxenite intrusions are characterized by Fe-rich pentlandite. Cr-spinel is associated with ilmenite and contains high concentrations of Ti. In general, the composition of Cr-spinel matches its formation in a continental setting (Barnes and Roeder, 2001).

The sulphide ores of the Alhadyr and Biryusa MUM intrusions are characterized by the dominant presence of sperrylite (PtAs2) with respect to other PGE minerals. Sperrylite is replaced by secondary minerals from PtAs2 to Ni5As8, then (Fe,Ni)3Pt2 and finally by PtCu. Sperrylite includes refractory Ir and Os as minor elements typical of most ESMP intrusions. The minerals of Pd, such as geversite (PtSb2), sobolevskite (PdBi), stibiopalladinite (Pd5Sb2), mertieite II (Pd8Sb3) and several unnamed phases (e.g. Pd5Bi2, Pd8Sb3), are enriched in Fe and Ni. The sulfide ores of the Barbitay ore cluster (Zhelos massif) are characterized by a variable PGE mineral assemblage dominated by PGE arsenides and sulfoarsenides: irarsite–platarsite– hollingworthite (Ir,Pt,Rh)AsS, sobolevskite, kotulskite Pd(Te,Bi), merenskyite–melonite (Pd,Ni)Te2, isomertieite

139

(Pd11Sb2As2), mertieite II, menshikovite (Pd3Ni2As3), majakite (PdNiAs), sperrylite (PtAs2), and omeiite (Os,Ru)As2. The proportions of PGE minerals in the different ores are variable even within one locality; they depend on host rock composition, ore type, and degree of secondary processes. Sperrylite is present in all rock associations, but the content of refractory PGE is variable. In general, the mineralogical and geochemical features found in the Precambrian ore-bearing complexes of the East Siberian LIP are indicative of a common magmatic source.

The compositional variations of Alkhadyr intrusions are defined by olivine fractionation. The calculated composition of primary magma corresponds to picrite containing more than 30% of olivine phenocrysts and about 27 wt.% MgO. The parental magma of the Yoko–Dovyren pluton was picritic in composition as well containing 40-50% of olivine (Ariskin et al., 2003).

We estimated the composition of an olivine-free melt for the Tartay massif (Alhadyr terrane): early olivine contained 10-12% of fayalite. The melt in equilibrium with that olivine contained 11–17 wt.% MgO. The other

calculated parameters of the initial melt correspond to picrobasalt. The enrichment of magmas in refractory PGE is indicative of a high degree of melting.

A gabbro of the Kingash massif (Kan block) yielded a U-Pb baddeleyite age of 726±18 Ma (Ernst et al., 2012). The age of the Yoko–Dovyren pluton is 731–723 Ma (Ariskin et al., 2012). Those ages match the 729–700 Ma age of ESMP volcanic rocks (Gladkochub et al., 2007). An olivine gabbro of the Tartay massif yielded a U-Pb zircon age of 712 Ma. Based on all those recent and new data, the Ioko–Dovyren–Kingash LIP was renamed to East Siberian metallogenic province. Conclusively, the ages of ore-bearing MUM intrusions of the whole ESMP are in the range of 731–710 Ma, i.e. similar to the 725–710 Ma age range of the Franklin LIP in Canada (Gladkochub et al., 2007; Ernst et al, 2012) and to that of the Rodinia breakup in Neoproterozoic time.

Acknowledgements This work supported by Program ONZ-2

from the Department of Geosciences of the Russian Academy of Sciences.

Fig.1. The location of the ore-bearing mafic-ultramafic complexes in the East Siberian metallogenic province. 1 – Siberian craton; 2 – exposures of the Precambrian basement of the Siberian craton; 3-7 – folded areas: 3 – Riphean, 4 - Riphean-Vendian, 5 – Early Caledonian, 6 – Late Caledonian, 7 – cover of the West Siberian Plate; 8 – ultramafic-mafic intrusions hosting PGE-Cu-Ni deposits and ore occurrences: 1 – Shumikha, 2,3 – Kingash, 4 – Golumbei, 5 – Tartai, 6 – Ognit, 7 – Zhelos, 8 - Tokty-Oi, 9 – Malyi Zadoi, 10 – Yoko-Dovyren.

I – Yenisei Ridge, II – Sayan area (Kan and Alkhadyr terranes), III – Baikal-Patom zone

140

References

Ariskin, A.A., Konnikov, E.G., Danyushevskii, L.V., MacNeal, E., Nikolaev, G.S., Kostitsyn, Yu.A., Kislov, E.V., Orsoev, D.A., 2012. The Dovyren intrusive complex: geochemistry, petrology, and history of sulfide saturation of parental magmas, in: Ultrabasic–Basic Complexes in Folded Areas and Their Minerageny. Proc. Fourth Int. Conf. and Third Youth School Seminar. Ekos, Ulan Ude, 17–20. [in Russian].

Ariskin, A.A., Konnikov, E.G., Kislov, E.V., 2003. Modeling of equilibrium crystallization of ultramafites as applied to the problem of formation of the phase layering of the Yoko-Dovyren pluton (northern Baikal area,

Russia). Geokhimiya 2, 131–155. [in Russian].

Barnes S.J. and Roeder P.L. 2001. The range of spinel compositions in terrestrial mafic and ultramafic rocks. J. Petrol. 42 (12), 2279–2302.

Gladkochub D.P., Wingate M.T.D., Pisarevsky S.A., Donskaya T.V., Mazukabzov A.M., Ponomarchuk V.A., Stanevich A.M., 2006. Mafic intrusions in southwestern Siberia and implications for a Neoproterozoic connection with Laurentia. Precambrian Res. 147, 260–278.

Ernst, R.E., Hamilton, M.A., Soderlung, U., 2012. A proposed 725 Ma Dovyren–Kingash LIP of southern Siberia, and possible reconstruction link with 725–715 Ma Franklin LIP of North Laurentia. Geol. Assoc. of Canada (GAC). Mineral. Assoc. Canada (MAC), Joint Ann. Meeting Geosci. at Edge, May 27–29, St. Johns, Newfoundland and Labrador, Canada.

Abstr. Vol. 35, 27-29. Mekhonoshin, A.S., Kolotilina, T.B., 2009. PGE-

Ni-sulfide mineralization of massifs in the Gutara–Uda metallogenic zone (southern Siberia). In: Ultrabasic–Basic Complexes of Folded Areas and Associated Deposits. Proc. Third Int. Conf. Ekaterinburg Vol. 2, 49–54. [in Russian].



Abstract Volume


Petrology and phase equilibria of charnockites:

implications for Precambrian crustal evolution

Toshiaki Tsunogae a,b, *, M. Santoshc

aFaculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan bDepartment of Geology, University of Johannesburg, Auckland Park 2006, South Africa cJournal Centre, China University of Geosciences Beijing, No. 29, Xueyuan Road, Haidian District,


Charnockites (orthopyroxene-bearing granitoids) constitute one of the dominant lithologies in many Precambrian high-grade metamorphic terranes worldwide (e.g., Frost and Frost, 2008; Rajesh and Santosh, 2012). They are regarded as a major constituent of the Precambrian lower crust because of the generally high temperature and anhydrous nature of these rocks. Charnockites are composed mainly of plagioclase, K-feldspar, quartz, and orthopyroxene with or without biotite, hornblende, garnet, ilmenite, and magnetite. They occur either as large massive bodies of possibly magmatic origin (e.g., Rajesh et al., 2012), or as patches or veins within foliated orthopyroxene-free felsic gneisses as ‘incipient charnockite’ (e.g., Pichamuthu, 1960) possibly formed by decreasing H2O activity during high-grade metamorphism (e.g., Janardhan et al., 1979; Santosh et al., 1990; Endo et al., 2012). In this study, we evaluate the petrogenesis of charnockites from different regions of the Gondwana fragments (Southern India, East Antarctica, Southern Africa) belonging to different ages (Neoarchean to Cambrian) based on phase equilibria modeling in the system NCKFMASHTO. The results suggest relatively wide P-T ranges for the stability of orthopyroxene-bearing mineral

assemblages in charnockites, although they are mostly narrowed down by isopleth calculations. The calculated P-T conditions for massive charnockites from the Salem Block (Southern India), Limpopo Complex (Southern Africa), and Napier Complex (Antarctica) are consistent with the peak P-T conditions of the regions, suggesting that the massive charnockite corresponds to crystallized dry felsic magma. On the other hand, P-T conditions estimated for incipient charnockite from the Trivandrum Block (Southern India), is ~100 °C lower than the peak P-T condition. The formation of incipient charnockite in this case is therefore inferred as a post-peak event. T-M(H2O) (mole H2O) diagrams suggest orthopyroxene-bearing mineral assemblages in massive and incipient charnockites are stable at low M(H2O) conditions of <0.5 mol.%, which is consistent with the occurrences of CO2-rich fluid inclusions that probably buffered the activity of H2O to low levels and form charnockitic mineral assemblages (e.g., Santosh and Omori, 2008; Touret and Huizenga, 2012). The occurrence of charnockite with various compositions formed in different tectonic settings suggests that formation of charnockite at dry conditions is a dominant process in the Precambrian lower crust.

References

Endo, T., Tsunogae, T., Santosh, M., Shaji, E., 2012. Phase equilibrium modeling of incipient charnockite formation in NCKFMASHTO and MnNCKFMASHTO systems: A case study from Rajapalaiyam, Madurai Block, southern India. Geoscience Frontiers 3, 801–811.

Frost, B.R., Frost, C.D., 2008. On charnockites. Gondwana Research 13, 30–44.

Janardhan, A.S., Newton, R.C., Smith, J.V., 1979. Ancient crustal metamorphism at low pH2O: charnockite formation at Kabbaldurga, south India. Nature 278, 511–514.

Pichamuthu, C.S., 1960. Charnockite in the making. Nature 188, 135–136.

Rajesh, H.M., 2012. A geochemical perspective on charnockite magmatism in

Peninsular India. Geoscience Frontiers 3,773–788.

Rajesh, H.M., Santosh, M., 2012. Charnockites and charnockites. Geoscience Frontiers 3, 737–744.

Santosh, M., Omori, S., 2008. CO2 flushing: A plate tectonic perspective. Gondwana Research 13, 86–102.

Santosh, M., Harris, N.B.W., Jackson, D.H., Mattey, D.P., 1990. Dehydration and incipient charnockite formation: a phase equilibria and fluid inclusion study from South India. Journal of Geology 98, 915–926.

Touret, J.L.R., Huizenga, J.M., 2012. Charnockite microstructures: From magmatic to metamorphic. Geoscience Frontiers 3, 745–753.



Abstract Volume


Recognition and tectonic implications of an extensive

Neoproterozoic volcano-sedimentary rift basin along the

southwestern margin of the Tarim Craton, northwestern

China

Chao Wanga*, Liang Liub, Yong-He Wanga, Shi-Ping Hea, Rong-She Lia, Alan S.

Collinsc, Meng Lia, Wen-Qiang Yangb, Yu-Ting Caod, Chao Shia, Hui-Yang Yua

aMLR Key Laboratory of Genesis and Exploration of Magmatic Ore deposits, Orogen Research Centre

of China Geological Survey, Xi'an Center of China Geological Survey, Xi'an 710054, China bState Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an

710069, China cCentre for Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, University of

Adelaide, SA 5005, Australia dCollege of Geological Science & Engineering, Shandong University of Science and

Technology, Qingdao 266510, China

The Tiekelik Belt includes a large outcrop of Precambrian continental crust, which is exposed along the southwestern margin of the Tarim Craton, NW China. It is characterized by the development of high-grade metamorphic rocks and volcano-sedimentary successions. In this contribution, we present ten samples of zircon U–Pb geochronological studies for provenance and age determination of this volcano-(meta)sedimentary succession, and geochemical analyses on basalts of the bimodal volcanic rocks from the Sailajiazitage Group. The basalts of the bimodal volcanic rocks from the Sailajiazitage Group show enrichment of light rare earth element (LaN/YbN = 4.92–8.51) and high field strength elements (HFSEs) (e.g. Nb, Zr and Ti), which are similar to continental flood basalts (CFB) indicating bimodal volcanism in a within-plate tectonic setting. Our new data, combined with

previous sedimentary facies analysis, supports the argument that a large Neoproterozoic volcano-sedimentary rift basin which records the change from a fluviolacustrine setting to a marine environment was associated with within plate volcanism in the southwestern margin of the Tarim Craton. The zircon U–Pb ages indicate that the initial rifting occurred at ca. 881 Ma and extensive rift took place at ca. 785 Ma in the southwestern margin of the Tarim Craton. The detrital zircon age pattern of the Tiekelik Belt is characterized by a prominent major percentage of Neoproterozoic zircons with four populations (ca. 630–669 Ma, ca. 785 Ma, ca. 739–746 Ma and ca. 848 Ma), followed by some Paleoproterozoic ones with ages between 1800 Ma and 2400 Ma and fewer Mesoproterozoic and Archaean zircon grains. Almost all the main detrital zircon populations approximately match the age of

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widespread magmatism documented in the northern margin of the Tarim Craton (Figure 1). We consider the sourcing of these components from the northern Tarim and Southern Tarim as an explanation for the features of the Tiekelik Neoproterozoic sediment age probability patterns, mainly the prominent Neoproterozoic and Paleoproterozoic components.

Figure 1 shows a detrital zircon dataset for the Tarim basin margin (Figure 1, A–F). The different detrital components and tectono-thermal evolution suggest that the South Altyn region does not correlate with other parts of the Tarim Craton. It seems likely that the lack of typical Tarim Paleoproterozoic and Archaean zircon detritus in the Neoproterozoic rocks in the South Altyn rules out the Tarim Craton as a potential source. The absence or rarity of Mesoproterozoic–early Neoproterozoic detritus within the late Neoproterozoic sediments in the Tarim Craton also argues against South Altyn as a sediment

source. We therefore suggest that South Altyn may represent an exotic terrane accreted to the Tarim after the late Neoproterozoic.

The extremely similar detrital zircon age spectra and the sedimentary system that the basins of the Tarim Craton share suggest that the Aksu, Kuluketage and Tiekelik areas had a similar provenance. Detrital zircon grains from these successions are dominated by Neoproterozoic and Paleoproterozoic ages inferred to have been derived from source terranes of the northern Tarim. We speculate that this might be linked to far-field tectonics related to uplift and erosion of the northern Tarim rocks and the predominantly large-scale southwards transport of sediments over the craton (Figure 1). Nevertheless, the rifting environment of the sedimentary basin in the Tiekelik region suggests a potential bidirectional source (Figure 1) (from the north and south of current direction).

References

Zhu, W.B., Zheng, B., Shu, L., Ma, D.,Wu, H., Li, Y., Huang,W., Yu, J., 2011b. Neoproterozoic tectonic evolution of the Precambrian Aksu blueschist terrane, northwestern Tarim, China: insights from LA-ICPMS zircon U–Pb ages and geochemical data. Precambrian Research 185, 215–230.

Xu, Z., Q., He, B.Z., Zhang, C.L., Zhang, J.X., Wang, Z.M., Cai, Z.H., 2013b. Tectonic framework and crustal evolution of the Precambrian basement of the Tarim Block in NW China: New geochronological evidence from deep drilling samples. Precambrian Research

235, 150-162. Zhang, Y.L., Wang, Z.Q., Yan, Z., Wand, T.,

Guo, X.Q., 2011b. Provenance of Neoproterozoic rocks in Quruqtagh area, Xinjiang: evidence from detrital zircon geochronology. Acta Petrologica Sinica 27, 121–132 (in Chinese with English abstract).

Wang, C., Liu, L., Yang, W.Q., Zhu, X.H., Cao, Y.T., Kang, L., Chen, S.F., Li, R.S., He, S.P., 2013. Provenance and ages of the Altyn complex in Altyn Tagh: implications for the early Neoproterozoic evolution of northwestern China. Precambrian Research 230, 193–208.

145

Fig. 1 location of Precambrian basement of the Tarim Craton and adjacent areas (modified after Lu et al., 2008) and probability plots of late Neoproterozoic (meta-) sedimentary units from the Tarim Craton. Data sources: Zhu et al. (2011b) Zhang et al. (2011b) Xu et al. (2013b) Wang et al. (2013, this study). n – number of detrital zircons age data. The dashed circles show the Precambrian rocks inferred from the drill holes



Abstract Volume


Zircon U-Pb geochronology, geochemical and Hf

isotopes of the Zhibenshan granitoid in Baoshan block: a

magmatic response to the Proto-Tethys evolution along

the northern margin of Gondwana

Changming Wanga, b,*, Jun Denga, T. Campbell Mccuaigb, Qingfei Wanga

aChina University of Geosciences, Beijing, 100083, China bCentre for Exploration Targeting, Australian Research Council *Corresponding author e-mail: [email protected]

In China, Qinling-Qilian-Kunlun and Longmu Tso-Shuanghu-Changning-Menglian Tethyan regions (Fig.1) are the important branches of the eastern tectonic belt, and thus bear significance for the development of the Tethyan belt within SE Asia. Two Tethyan regions mainly consist of continental blocks and tectonic sutures along the northern margin of Gondwana. The tectonic framework and magmatic evolution have attracted attention in term of the geochronology and geochemistry of the cherts and the mafic and ultramafic rocks in suture zones, and the igneous rocks within the blocks (e.g., Liu et al., 1993; Mo et al., 1993; Zhong et al., 1998; Pan et al., 2003; Metcalfe, 2013). However, exploration and research activities have largely focused on the Paleo-Tethys, Meso-Tethys to Neo-Tethys, and no detailed Proto-Tethys has been attempted (e. g., Cheng, 1987; Sengor, 1987; Shi et al., 1989; Liu et al., 1993; Hou et al., 2007; Metcalfe, 2013; Deng et al., 2014; Wang et al., 2014a, b). In this paper, we present zircon LA-ICP-MS age, Hf-isotope, whole-rock major and trace element of the Ordovician Zhibenshan magmatic rocks in the Baoshan Black with regard to: (1) constraints on the formation age, (2) nature of the magma

source region and magma evolution, and (3) tectonic setting and implications for magmatism. We also attempt to discuss the problem of whether a ‘Proto-Tethys Ocean’ existed in the Changning-Menglian Tethyan region during Earth’s early period, which can provide a useful basis for the tectonic and magmatic evolution of Tethys.

Zircon U–Pb dating for Zhibenshan granitoid yields a crystallization age of 457–470 Ma, with in situ Hf isotopic analyses for the same zircons of εHf (t) ranging from −13.7 to −2.8, corresponding to Hf crustal model ages (TDM2) of 2.3–1.6 Ga. These granitoids are mainly high-K calc-alkaline and show fractionated I-type affinities. These geochemical features allowed us to conclude that the primary magma of the Zhibenshan granitoid was probably derived from partial melting of underlying Proterozoic meta-sedimentary rocks with addition of mantle-derived magmas, accompanied by fractional crystallization. We infer, therefore, that the Baoshan Block may also have formed part of Gondwana. Moreover, we suggest that the Early Paleozoic magmatism was attributed to the evolution of the Proto-Tethyan Ocean along the northern margin of Gondwana.

http://petrology.oxfordjournals.org/search?author1=T.+Campbell+Mccuaig&sortspec=date&submit=Submit


Fig. 1 (a) Generalized geological map of China showing the Proto-Tethys suture zones and localities of dated rocks by zircon SHRIMP/LA-ICP-MS U–Pb method (modified after Wang and Mo, 1995; Zhai and Deng, 1996; Khin Zaw, 2007; Wang et al., 2014a). (b) Simplified geological map showing the granitoids in the Tengchong and Baoshan blocks (modified after Wang et al., 2014). (c) Simplified geological map showing the Zhibenshan granitoids (modified after Liao et al., 2013). Abbreviations, QSZ = Qinling suture zone; QLSZ = Qilian suture zone; KLSZ = Kunlun suture zone; LLSZ = Longmu Tso-Shuanghu suture zone; CMSZ = Changning-Menglian suture zone; WQT = Western Qiangtang terrane; EQT = Eastern Qiangtang terrane; LT = Lhasa terrane; HT = Himalaya terrane.



Abstract Volume


Petrology, geochemistry and petrogenesis of Ganzhou

granites in Jiangxi Province

Lili Wang*, Zhidan Zhao, Xuanxue Mo

School of Earth Science and Resources, China University of Geosciences (Beijing), Beijing 100083,

China *Corresponding author e-mail: [email protected]

The subduction of the Paleo-Pacific oceanic plate under the Eurasian Plate and the North American Plate is one of the most important geological events in the geologic history of East Asia, which led to the development of a large area of magmatic rocks and some of the world class ore deposits near the Pacific rim. The Andean-type active continental margin and the Western Pacific-type margins were also created after this subduction, the former was characterized by the development of continental arcs, and the latter resulted in the development of marginal oceanic basins between the continents and island arcs.

Here we present results from nine magmatic intrusions from Ganzhou in Jiangxi Province of South China. Their major element chemistry show weakly peraluminous nature, and the rocks classify mainly as high-K calc-alkaline series. The element oxides show good linear relationship in the Harker diagrams. Most of the samples are enriched in LREE and depleted in HREE, except one rock pluton, without significant depletion of Zr and Hf. The strongly negative Eu anomalies of the granitic rocks in all cases suggest plagioclase as a residual phase during the partial melting processes.

We also present zircon U-Pb and Lu-Hf data on the granitoids and formulate a geodynamic model to address the transformation of the tectonic regime.




Abstract Volume


Metallogenic fingerprints of north China and Yangtze

craton of China: A comparison with Gondwana cratons

Yang Wang

School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China

Tectonic domains are metallogenically distinct in that their mineral deposits contain different mixtures of metallic elements from domain to domain (de Wit and Thiart, 2005). Metallogenic provinces represent regional geochemical heterogeneities in the crust, evidence for which remains encoded in each province as unique metallogenic ‘fingerprints’. The geological and mineral deposit data of North China and Yangtze craton of China used for this study are compiled from the atlases of the China Geological Map and the Metal Resources of China. Meanwhile, the data for the cratons of Gondwana super-continent are taken from Thiart and de Wit (2006). According to their geochemical affinities, six element groups were selected for analyses. The six element groups, and the total number of deposits in which these groups occur in the North China and Yangtze craton are tabulated. In total there are 1399 deposits spread over North China and Yangtze craton.

The metallogenic fingerprints of fragments of continental crust can be calculated through their spatial association with a combination of six element groups (e.g., Au, CrNiPGETi, CuPbZnBa, SnSb, W, and UThREE), using the spatial coefficient (rij) proposed by de Wit and Thiart (2005). The spatial coefficient (rij) represents the proportion of deposits that occur in the specified craton per unit area. The value of the spatial coefficient ranges from 0 to infinity; it is equal to 1 if there is no spatial association

between a craton and an element group. There is a positive association between mineral j and craton i for values of natural log of rij, ln(rij) > 0; and a negative association was represented by ln(rij) < 0.

The mineralization in the less-developed cratons may not be adequately represented in the database. This problem is tackled by weighting the spatial coefficient, with an ‘exploration index’. The definition and calculation method of ‘exploration index’ and ‘weighted’ spatial coefficient (rw

ij) are taken from Thiart and de Wit (2006). In this study, the gross national income per capita (GNI-C) from the World Bank are estimated to calculated exploration index using the United States as a benchmark (e.g., the US has an exploration index of 1). The interpretation of rw

ij is the same as in that of the unweighted spatial coefficient. The natural logs of the spatial coefficients (ln(rij)) and the ‘weighted’ spatial coefficients (ln(rw

ij)) for the two cratons of China and 11 cratons of Gondwana super-continent and the six selected element groups is given in Fig.1. Figure 2 represents the total spatial coefficient combining all sets of elements (e.g., all six element groups) for each cratons; these are the ‘metallogenic fingerprints’ of the 13 cratons. Where values are high, the imprint of total mineralization is high relative to the other domains: metaphorically a ‘strong fingerprint’. Compared with the fingerprint of the cratons of Gondwana super-continent, the North China craton is relatively

150

enriched in gold and Cu-Pb-Zn-Ba element groups, but significantly depleted in Sn-Sb and W groups. Meanwhile, the Yangtze craton exhibits enrichment of Cu-Pb-Zn-Ba, and average value for U-Th-REE element groups, but slightly depleted values for gold and W.

Acknowledgements This study is financially supported by the

Fundamental Research Funds for the Central Universities, grants No.2652013021 and No.2010ZD15.

Fig. 1 Mineral diversity of the two cratons of China and 11 cratons of Gondwana super-continent. Solid bars represent the ‘raw’ spatial coefficient (ln(rij)); grey bars represent the weighted spatial coefficient (ln(rw

ij)) between specific element(s) and the corresponding crust ‘weighted’ with their exploration indices. AM: Amazonia, CO: Congo, KP: Kaapvaal, LM: Leo-Man, LP: Limpopo, NC: North China, PL: Pilbara, RE: Requibath, SF: Sao Francisco, TZ: Tanzania, YL: Yilgarn, YZ: Yangtze, ZB: Zimbabwe

Fig. 2 Mineral diversity measure between all combined elements of mineral deposits of the 13 cratons of China and Gondwana super-continent.

References

de Wit, M.J., Thiart, C., 2005. Metallogenic fingerprints of Archean Cratons. In: MacDonald, I., Boyce, A.J., Butler, I.B., Herrington, R.J. (eds.), Mineral Deposits and Earth Evolution. Geological Society, London, Special Publication 248, 59–70.

Thiart, C., de Wit, M.J., 2006. Fingerprinting the metal endowment of early continental crust to test for secular changes in global mineralization. In: Kesler, S.E., Ohmoto, H. (eds.), Evolution of Early Earth’s Atmosphere, Hydrosphere, and Biosphere—Constraints

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from Ore Deposits. Geological Society of America Memoir 198: 53–66.



Abstract Volume


High Ba-Sr Guojialing-type granitoids in Jiaodong

Peninsula, east China: petrogenesis and geodynamic

implications

Zhong-Liang Wanga, Li-Qiang Yanga, *, Hua-Feng Zhanga, Yue Liua, Bing-Lin

Zhanga, Tao Huanga, Xiao-Li Zhengb, Rong-Xin Zhaoc

aState Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences,

Beijing 100083, China bShandong Gold Mining Stock Co. Ltd, Laizhou city, Shandong Province 261400, China cXincheng Gold Company, Shandong Gold Mining Stock Co. Ltd, Laizhou city, Shandong Province

261438, China *Corresponding author e-mail: [email protected]

The Jiaodong Peninsula, the largest gold producer in China (Deng et al., 2006, 2008; Yang et al., 2006, 2009; Goldfarb and Santosh, 2014; Yan et al., 2014), is located along the southeastern margin of the North China Craton (NCC) (Deng et al., 2003, 2009; Yang et al., 2008, 2014a, b).The widespread magmatism in Jiaodong can be divided into three phases: Late Triassic (215–200 Ma), Late Jurassic (166-149 Ma) and Early Cretaceous (132-110 Ma) (Zhang et al., 2010; Jiang et al., 2012). The majority of gold resources (>95%) in Jiaodong are hosted in the Late Jurassic and Early Cretaceous granitoids (Goldfarb and Santosh, 2014; Li et al., 2013; Zhai and Santosh, 2013; Fig. 1b), however, the petrogenesis of the granitic rocks, especially the Early Cretaceous Guojialing-type granitoids, remains controversial (Hou et al., 2007; Zhang et al., 2010; Yang et al., 2003, 2012). The Guojialing-type granitoids, intruding the Linglong-type granitoid, include six plutonic bodies from the west to east through the Jiaodong peninsula: Sanshandao, Xincheng, Shangzhuang, Beijie, Congjia and Guojialing, of which the Xincheng pluton is the only

Guojialing-type granitoid that hosts the super-large gold deposit in Jiaodong (Wang et al., 2014). The Xincheng pluton, intruding the Linglong biotite-granite, mainly consists of quartz monzonite and monzogranite. The boundary between the quartz monzonite and monzogranite is unclear, suggesting that they are coeval intrusions. In order to discuss the petrogenesis of the Xincheng Early Cretaceous granitoids, and reveal the geodynamic back ground for the high Ba-Sr Guojialing-type granitoids, this study systematically investigated the Xincheng pluton to sample the monzogranite, and conducted LA-ICP-MS zircon U-Pb dating, major and trace elements geochemical, mineral chemical, Lu-Hf and Sr-Nd isotopic analysis.

LA-ICP-MS zircon dating yielded the magma crystallization ages of 127±2 to 129±1 Ma for the Xincheng monzogranite, consistent with the LA-ICP-MS U-Pb ages of 126–132 Ma for the other Guojialing-type granitoids (Hou et al., 2007, Yang et al., 2012). In addition, two groups of inherited ages of 143–148 Ma, and 2322–2524 Ma can be identified. The Xincheng monzogranites show high alkali contents (K2O +


153

Na2O = 7.03–8.68%), low Al2O3 (14.41–15.54) and MgO (0.21–0.62%) values and relatively flat HREE patterns, which are in contrast with the calc-alkaline characteristics of the adakitic rocks. The high Ba (853–2117 ppm), Sr (634–1019 ppm), K/Rb (>329) and light REEs (65–204), and low Rb (55.5–103 ppm), Th (<27 ppm), U (<5.87 ppm), Nb (<10.8 ppm), Ta (<1.06 ppm), Y (<17 ppm) and heavy REEs (<18.3 ppm), and lack of apparent negative Eu anomaly and depletion of Nb in spidergrams distinguish them from I-, S-, M- and A-type granites. Nevertheless, the high Ba (>853 ppm) and Sr (>634 ppm) concentrations reveal that the Xincheng monzogranites are akin to the high Ba-Sr granites defined by Tarney and Jones (1994) based on high Sr (>300 ppm) and Ba (>500 ppm) contents.

The plagioclases and K-feldspars in the monzogranites both show reverse zoning texture, of which the plagioclases belong to oligoclase with An contents of 12.87–22.91%, and the K-feldspars belong to orthoclase with Or contents of 81.24–93.69%. The Xincheng monzogranites have negative zircon εHf(t) values ranging from –24.7 to –18.1, overlapping those of zircons from the Linglong suite (εHf(t)= –28.7 to –17.6) widely accepted to have been originated from partial melting of the continental crust of the Jiaobei terrane (Yang et al., 2012), and have the two-stage Hf model ages (TDM2) of 2051 to 2413 Ma. They have 87Sr/86Sr (Isr) and εNd(t) values of 0.71071~0.71172 and –17.1~–21.3, similar to those of the Linglong biotite granite, and show

the two-stage Nd model ages (TDM2) of 2310~2648 Ma.

Based on the detailed elemental, mineralogical, and Lu-Hf and Sr-Nd isotopic data, we suggest that the Xincheng monzogranites were most likely generated by partial melting of the basement rocks of the Jiaobei terrane with minor addition of intermediate magma which were partial melts of juvenile mafic lower crust. In combination with previous investigations, it is regarded that subduction of the paleo-Pacific slab beneath the North China Craton (NCC) and associated asthenosphere upwelling were most likely the mechanism associated with the generation of the high Ba-Sr granites. Acknowledgments

Thanks are given to Prof. Jun Deng and Qingjie Gong at China University of Geosciences (Beijing) for the comments and suggestions on this manuscript. This study was financially supported by the National Natural Science Foundation of China (Grant No. 41230311, 40872068, 40672064 and 40572063), the National Science and Technology Support Program (Grant No. 2011BAB04B09), the Program for New Century Excellent Talents (Grant No. NCET-09-0710), 111 Project (Grant No. B07011) and Changjiang Scholars and Innovative Research Team in University, the Ministry of Education, China (Grant No. IRT0755). This work also contributes to the Talent Award to M. Santosh under the 1000 Plan from the Chinese Government.

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Deng, J., Yang, L.Q., Ge, L.S., Wang, Q.F., Zhang, J., Gao, B.F., Zhou, Y.H., Jiang, S.Q., 2006. Research advances in the Mesozoic tectonic regimes during the formation of Jiaodong ore cluster area. Progress in Natural Science 16, 777-784.

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Q.J., Zhao, J., Liu, H., 2009. Self-similar fractal analysis of gold mineralization of Dayingezhuang disseminated-veinlet deposit in Jiaodong gold province, China. Journal of Geochemical Exploration 102, 95-102.

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Zhao, K.D., 2007. Contrasting origins of late Mesozoic adakitic granitoids from the northwestern Jiaodong Peninsula, East China: Implications for crustal thickening to delamination. Geological Magazine, 144, 619-631.

Jiang, N., Chen, J.Z., Guo, J.H., Chang, G.H., 2012. In situ zircon U-Pb, oxygen and hafnium isotopic compositions of Jurassic granites from the North China craton: Evidence for Triassic subduction of continental crust and subsequent metamorphism-related 18O depletion. Lithos 142, 84-94.

Li, X.C., Fan, H.R., Santosh, M., Hu, F.F., Yang, K.F., Lan, T.G., 2013. Hydrothermal alteration associated with Mesozoic granite-hosted gold mineralization at the Sanshandao deposit, Jiaodong gold province, China. Ore Geology Reviews 53, 403-421.

Tarney, J., Jones, C.E., 1994. Trace element geochemistry of orogenic igneous rocks and crustal growth models. Journal of the Geological Society 151, 855-868.

Wang, ZL, Yang, LQ, Deng, J, Santosh, M, Zhang, HF, Liu, Y, Li, RH, Huang, T, Zheng, XL and Zhao, H. 2014. Gold-hosting high Ba-Sr granitoids in the Xincheng gold deposit, Jiaodong Peninsula, East China: Petrogenesis and tectonic setting. Journal of Asian Earth Sciences. doi: http: // dx.doi.org /1 0.1016/j.jseaes.2014.03.001

Yan, Y.T., Zhang, N., Li, S.R., Li, Y.S., 2014. Mineral chemistry and isotope geochemistry of pyrite from the Heilangou gold deposit, Jiadong Peninsula, Eastern China. Geoscience Frontiers 5, 205-213.

Yang, J.H., Chu, M.F., Liu, W., Zhai, M.G., 2003. Geochemistry and petrogenesis of Guojialing granodiorites from the northwestern Jiaodong Peninsula, eastern China. Acta Petrologica Sinica 19(4), 692-700 (in Chinese with English abstract).

Yang, K.F., Fan, H.R., Santosh, M., Hu, F.F., Wilde, S.A., Lan, T.G., Lu, L.N., Liu, Y.S., 2012. Reactivation of the Archean lower crust: implications for zircon geochronology,

elemental and Sr-Nd-Hf isotopic

geochemistry of late Mesozoic granitoids from northwestern Jiaodong Terrane, the North China Craton. Lithos 146, 112-127.

Yang, L.Q., Deng, J., Wang, Q.F., Zhou, Y.H., 2006. Coupling effects on gold mineralization of deep and shallow structures in the Northwestern Jiaodong Peninsula, Eastern China. Acta Geologica Sinica 80, 400-411.

Yang, L.Q., Deng, J., Zhang, J., Guo, C.Y., Gao, B.F., Gong Q.J., Wang Q.F., Jiang, S.Q. Yu, H.J., 2008. Decrepitation Thermometry and Compositions of Fluid Inclusions of the Damoqujia Gold Deposit, Jiaodong Gold Province, China: Implications for Metallogeny and Exploration. Journal of China University of Geosciences 19, 378-390.

Yang, L.Q., Deng, J., Guo, C.Y., Zhang, J., Jiang, S.Q., Gao, B.F., Gong Q.J., Wang, Q.F., 2009. Ore-forming fluid characteristics of the Dayingezhuang gold deposit, Jiaodong gold province, China. Resource Geology 59, 182-195.

Yang, L.Q., Deng, J., Goldfarb, R.J., Zhang. J., Gao, B.F., and Wang, Z.L., 2014a. 40Ar/39Ar geochronological constraints on the formation of the Dayingezhuang gold deposit: new implications for timing and duration of hydrothermal activity in the Jiaodong gold province, China. Gondwana Research, 25: 1469-1483.

Yang, Q.Y., Santosh, M., Shen, J.F., Li, S.R.,

2014b. Juvenile vs. recycled crust in NE China: Zircon U-Pb geochronology, Hf isotope and an integrated model for Mesozoic gold mineralization in the Jiaodong Peninsula. Gondwana Research Gondwana Research, 25: 1445-1468.

Zhai, M.G., Santosh, M., 2013. Metallogeny of the North China Craton: Link with secular changes in the evolving Earth. Gondwana Research 24, 275-297.

Zhang, J., Zhao, Z. F., Zheng, Y. F., Dai, M., 2010. Postcollisional magmatism: Geochemical constraints on the petrogenesis of Mesozoic granitoids in the Sulu orogen, China. Lithos 119, 512-536.



Abstract Volume


155

Terminal events in the eastern segment of the central

Asian orogenic belt

Simon A. Wilde

The Institute for Geoscience Research, Curtin University,

Perth, Australia

The Central Asian Orogenic Belt (CAOB) extends for ca. 2500 km from the Urals and Kazakhstan in the west to the Sea of Japan in the east, and from the Siberian Craton in the north to the Tarim and North China cratons in the south. Although its earliest components are Neoarchean in age, it is predominantly composed of juvenile crustal rocks that evolved in Phanerozoic arc complexes and were accreted during the closure of the Paleo-Asian Ocean, with the subsequent emplacement of huge volumes of granitic magma in the late Paleozoic to Mesozoic. Arc accretion took place along both the northern and southern margins of the Paleo-Asian Ocean, with welding of terranes to the Siberian and Chinese cratons, respectively. Closure of the Paleo-Asian Ocean is generally considered to have started in the west, with final closure taking place along the Mongol-Okhotsk suture in the Russian Far East in the Early Cretaceous.

In the eastern segment of the CAOB, the Solonker-Xra Moron-Changchun suture zone is widely considered to mark the boundary between the Siberian and Chinese blocks, with most studies favouring closure in the Late Permian (Xiao et al., 2003; Wu et al., 2007). The main driving force controlling the evolution of the Paleo-Asian Ocean was the drift of the Tarim and North China blocks from a peri-Gondwana position northward toward the Siberian Craton. Voluminous granitoids and coeval volcanic rocks are a dominant feature throughout the eastern CAOB. Although local Permo-Carboniferous granites have been recorded from several areas, Triassic A-types were more widely emplaced during extension that followed the closure of the Paleo-Asian Ocean, possibly

as the result of slab breakoff (Wu et al., 2010). However, the most abundant and widespread granitoids are of Jurassic and Cretaceous age. The Jurassic granites are predominantly fractionated I-types that resulted from melting of juvenile crust generated from various mixtures of lower crust and underplated basaltic material (Wu et al., 2003). They are generally considered to result from the onset of Pacific plate subduction from the east and to define a compressional environment at this time (Wu et al., 2010). By contrast, Cretaceous magmatic rocks include both I- and A-types, considered to have formed in an extensional environment (Wu et al., 2010). The granites therefore record a transition from collisional to extensional tectonics, with a distinct younging to the east. Extension at this time is also evident from the development of several sedimentary basins, including the major Songliao Basin. The reason for this switch from compressional to extensional tectonics has been variously attributed to delamination or Pacific-plate roll-back (Wu et al., 2010).

Along the Pacific margin of both China and Far East Russia, the CAOB is terminated to the east by north-trending Mesozoic to Cenozoic accretionary terranes; the Nadanhada Terrane in China and the Sikote-Alin Terrane farther east in Russia formed here in the Jurassic-Cretaceous. The Nadanhada Terrane is intruded by undeformed Cretaceous granites with an age of ~125 Ma (Wu et al., 2010). The Sikhote-Alin terrane is characterized by Carboniferous to middle Jurassic olistoliths within a matrix of post-middle Jurassic clastic sediments overlain by early Cretaceous volcanic rocks that post-date accretion. It is common practice to separate these

156

accreted terranes from the CAOB, thereby defining the CAOB as consisting of those terranes amalgamated as a result of closure of the Paleo-Asian Ocean.

However, this distinction is not entirely clear-cut: the problematical terrane being the compound Bureya-Jiamusi-Khanka block, which has variously been considered to be the eastern part of the CAOB (Zhang et al., 2011; Zhou et al., 2009), a fragment of Gondwana (Wilde et al., 2000), a terrane rifted from Siberia (Wilde et al., 1999, Zhou et al., 2010) or an exotic block of unknown affinity (Wu et al., 2007). There is marked similarity between the Jiamusi and Khanka blocks in terms of both rock-types and their ages. There are less data available for the Bureya Block in Russia, but at least some components are similar in age and rock-type to the Jiamusi Block to the south. Hence, it is widely argued that they form a contiguous terrane. In China, the blocks that are generally agreed to make up the eastern part of the CAOB are, from west to east, the Erguna, Xing’an, and Songliao blocks, with the Liaoyuan Terrane separating these from the North China Craton. The Jiamusi Block lies to the east of the Songliao Block, with its western margin marked by the Heilongjiang Complex, a high-pressure blueschist terrane composed of basaltic rocks formed between 260 and 220 Ma and metamorphosed in the Early Jurassic. Similarities in the inherited zircon populations to the Songliao Block to the west led Zhou et al. (2009) to consider the Jiamusi Block as a part of the CAOB that rifted away in the Permo-Triassic, only to be re-amalgamated in the earliest Jurassic as a result of Pacific plate subduction. Wu et al. (2007) agreed with the latter-stage history, but considered the Jiamusi Block to be an exotic fragment driven westward by paleo-Pacific subduction. However, khondalitic sediments, uniformly metamorphosed to granulite facies at 500 Ma, have been identified in the Jiamusi, Xing’an and Erguna blocks (with detrital zircons of this age also present in the Songliao Block), providing further support that the Jiamusi Block was initially part of the CAOB.

The Heilongjiang Complex provides additional key evidence for determining the tectonic transition from events associated with the Paleo-Asian Ocean and the onset of Paleo-Pacific activity. Metamorphism of the Heilongjiang Complex to epidote-blueschist facies took place in the Late Triassic to Early Jurassic (Wu et al., 2007, Zhou et al., 2009), constrained by the youngest detrital zircon age and argon and Rb-Sr data recording ages of ~185-175 Ma. The wider implication of this finding is that the northward drift of the peri-Gondwana blocks, which include the Tarim and North and South China cratons (Zhao et al., 1996, Wilde et al., 1999), had ceased by the Permo-Triassic and was replaced in the earliest Jurassic by westward-directed Pacific-plate subduction as the dominant regional tectonic force from this time onward.

Later, a switch in tectonic regime occurred between 150–140 Ma, resulting in the cessation of compressional tectonics and its replacement by crustal extension with the generation of several non-marine basins. The largest and most economically important of these is the Songliao Basin, which hosts major oil and gas reserves. Recent work has established that the earliest components of the Songliao Basin are ~130 Ma in age. The reason for crustal extension at this time has been variously attributed to lithospheric delamination or Pacific plate roll-back. The eastward younging in magmatism from the Erguna Block in the west to the Pacific margin favours the roll-back model (Sun et al., 2013).

Final activity resulted in formation of the Nadhanada and Sikhote-Alin accretionary complexes, developed along the Pacific margin and comprising marine sediments intruded by Cretaceous granites. Recent work on the Nadanhada Complex indicates that the Raohe Complex was formed between 170 and 135 Ma. However, the Yuejinshan Complex, which is located closest to the CAOB, contains metabasalts with ages similar to the Heilongjiang Complex, suggesting complex multiple accretion along the Pacific margin in the Late Triassic-earliest Jurassic.

References

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bimodal composite dyke complex in the Jiamusi Block, NE China: An indication of

157

lithospheric extension driven by Paleo-Pacific roll-back. Lithos 162-163, 317-330.

Wilde, S.A., Dorsett-Bain, H.L., Lennon, R.G., 1999. Geological setting and controls on the development of graphite, sillimanite and phosphate mineralisation within the Jiamusi Massif: An exotic fragment of Gondwanaland located in North-Eastern China? Gondwana Research 2, 21–46.

Wilde, S.A., Zhang, X.Z., Wu, F.Y., 2000. Extension of a newly-identified 500 Ma metamorphic terrain in Northeast China: further U–Pb SHRIMP dating of the Mashan Complex, Heilongjiang Province, China. Tectonophysics 328, 115–130.

Wu, F.Y., Jahn, B.M., Wilde, S.A., Lo, C.H., Yui, T.F., Lin, Q., Ge, W.C., Sun, D.Y., 2003: Highly fractionated I-type granites in NE China (II): isotopic geochemistry and implications for crustal growth in the Phanerozoic. Lithos 67, 191-204.

Wu, F.Y., Sun, D.Y., Ge, W.C., Zhang, Y.B., Grant, M.L., Wilde, S.A., Jahn, B.M., 2010. Geochronology of the Phanerozoic granitoids in northeastern China. Journal of Asian Earth Sciences 41, 1-30.

Wu, F.Y., Yang, J.H., Lo, C.H., Wilde, S.A., Sun, D.Y., Jahn, B.M., 2007. The

Heilongjiang Group: a Jurassic accretionary

complex in the Jiamusi Massif at the western Pacific margin of northeastern China. The Island Arc 16, 156–172.

Xiao, W.J., Windley, B., Hao, J., Zhai, M.G., 2003. Accretion leading to collision and the Permian Solonker suture, Inner Mongolia, China: termination of the Central Asian Orogenic Belt. Tectonics, 2002TC001484.

Zhang, F.Q., Chen, H.L., Yu, X., Dong, C.W., Yang, S.F., Pang, Y.M., Batt, G.E., 2011. Early Cretaceous volcanism in the northern Songliao Basin, NE China and it geodynamic implication. Gondwana Research 19, 163-176.

Zhao, C.J., Peng, Y.J., Dang, Z.X., 1996. The Formation and Evolution of Crust in Eastern Jilin and Heilongjiang Provinces. Liaoning University Press, Shenyang, pp. 1-226 (in Chinese with English abstract).

Zhou, J.B., Wilde, S.A., Zhang, X.Z., Zhao, G.C., Zheng, C.Q., Wang, Y.J, Zhang, X.H., 2009: The onset of Pacific margin accretion in NE China: Evidence from the Heilongjiang high-pressure metamorphic belt. Tectonophysics 478, 230–246.

Zhou, J.B., Wilde, S.A., Zhao, G.C., Zhang, X.Z., Wang, H., Zeng, W.S., 2010. Was the easternmost segment of the Central Asian Orogenic Belt derived from Gondwana or Siberia: an intriguing dilemma? Journal of Geodynamics 50, 300-317.



Abstract Volume


Significant counterclockwise rotations of the Yanshiping

region, east North Qiangtang terrane, implication on the

initial collision of the Lhasa and Qiangtang terranes

during late Jurassic

Maodu Yana, Haidong Rena Xiaomin Fanga, Chunhui Songb, Dawen Zhanga

aKey Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research,

Chinese Academy of Sciences, Beijing 100101, China bSchool of Earth Sciences & Key Laboratory of Mineral Resources in Western China, Lanzhou University,

Lanzhou 730000, China

The Tibetan Plateau consists of multiple terranes, such as, from north to south, including the Qilian-Qaidam, Songpan-Ganzi, Qiangtang, Lhasa terranes, etc. These terranes have amalgamated from the south to Eurasia, one after another, during different periods; and finally, the Cenozoic continuous indentation of India into Eurasia has produced this present largest and highest plateau in the world.

As a natural laboratory of geodynamics and mountain building of intra-continental collision, much of the work has been done on the mechanisms and kinematics of India-Asia collision and the processes of plateau uplift. The work has established basic understanding on the evolution of the Tibetan Plateau, though debates still remain. Little work has been carried out on the evolution of the ‘proto-Tibet’. Knowledge of the evolution of ‘proto-Tibet’ would provide comprehensive understanding on the evolution of the Tibetan Plateau.

We present here detailed paleomagnetic rotation study on four middle-late Jurassic formations in the Town of Yanshiping, east North Qiangtang terrane, central Tibet. The four formations are, from lower to upper, the Quemocuo, Buqu, Xiali and Suowa Fms, which

are layers of sandstones, limestones, sandstones and limestones, respectively. A total of ~100 sites of ~1200 paleomagnetic samples have been collected. After performing thermal and/or AF demagnetization treatments, principle component analyses were utilized to obtain characteristic magnetization (ChRM) directions. These ChRM directions, some are obviously remagnetized, some pass field test and are believed to be primary directions.

These primary directions yield Ds = 335.3°, Is = 29.4°, α95 = 16.3°, N = 11 for the Quemocuo Fm., Ds = 331.3°, Is = 34.7°, α95 = 4.6°, N = 23 for the Buqu Fm., Ds = 321.3°, Is = 39.2°, α95 = 14.9°, N = 7 for the Xiali Fm., and Ds = 2.0°, Is = 43.5°, α95 = 21.2°, N = 4 for the Suowa Fm. The results indicate insignificant (possibly slightly clockwise) rotations among the Quemocuo, Buqu and Xilia Fms., but significant counterclockwise rotations from the Xialia to Suowa Fms. Combined with other geological evidences, this apparent transition from insignificant rotations to significant counterclockwise rotations during the Xiali Fm. might indicate the initial collision of Lhasa with Qiantang terranes during the period.



Abstract Volume


Mesozoic gold metallogenic system of the Jiaodong gold

province, eastern China

Liqiang Yang*, Jun Deng, Zhongliang Wang, Liang Zhang and Linnan Guo

State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences,


1 Geological setting and metallogenic characteristics

Jiaodong peninsula is the most important

gold concentration area of China, more than 150 gold deposits within it have been found and the proven gold reserves add up to 4000 tons (Yang et al., 2014). These gold deposits have almost the same metallogenic geodynamics background, ore-host rock environment, gold occurrence conditions and metallogenic characteristics, even though the gold occurrence conditions and mineralization types are diverse.

Jiaodong area is an endogenic hydrothermal gold- concentrated area consisting of Precambrian base rocks and ultra-high pressure (UHP) metamorphic rocks, with frequent tectonism and magmatism in Mesozoic (Tang et al., 2007; Ayers et al., 2002). Gold metallogenic events (about 130 to 110 Ma) happened ca. 2 Ga later than the regional metamorphism (Deng et al., 2006). Regional gold metallogenic system formed in the early Cretaceous continental-margin extension tectonic background. Large-scale gold metallogenic events happened in the process of regional NW extension changing to NE extension followed by the NEE compression (Goldfarb and Santosh, 2014), which corresponded to the large-scale lithosphere reduction in East China, North China craton destruction and the peak of continental rifting.

Gold deposits clustered around the NNE

Linglong, Queshan and Kunyushan metamorphic core complex, mainly along the regional NE-NNE detachment faults resulting from the contact zone of Precambrian metamorphic rocks and Mesozoic granites (Goldfarb et al., 2001). The ore-controlling fault belts went through a structure superposition of early ductile-brittle deformation and late brittle deformation (Yang et al., 2007). They extended in smooth-out waveforms in 3D space and controlled the lateral trending and subsection enrichment of gold ore bodies.

The mineralization types mainly include clastic altered (breccia) rock type, (sulphide-)quartz vein type and compound vein-belt type, with textures like the crush texture, crystalline-granular texture, interstitial texture and structures like the disseminated structure, vein structure, massive structure, crumby structure dominant in the ores (Deng et al., 2014a). This indicates that the ore-forming environment changed from ductile-brittle conditions to brittle conditions. Metallic minerals mainly include pyrite, chalcopyrite, galena and sphalerite, non-metallic minerals mainly include quartz, sericite, potash-feldspar and calcite. Gold minerals mainly include electrum, natural gold and a small amount of küstelite, which mainly occurs in the fractures of pyrites and quartz in the form of visible gold, lesser in crystal gaps or inclusions. Hydrothermal alteration types are mainly


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pyritization, silicification, sericitization and carbonatation, while ore-forming elements mainly consist of the Au-Ag (-Cu-Pb-Zn) assemblage (Wang，2012). The alteration and mineralization assemblage mentioned above show characteristics of mesothermal-epithermal assemblage.

Ore-forming fluids came from both the crust and mantle and are mainly the crustal sources of metamorphic fluids (Yang et al., 2009; Guo et al., 2014; Li and Santosh, 2014). Metallogenic materials were derived from the Precambrian metamorphic basement rock mass which was reactivated in the Mesozoic, mingling with a small amount of the shallow crustal and mantle components (Wang et al., 2014a; Zhang et al., 2014).

The consistency of regional metallogenic characteristics indicate that the early Cretaceous large-scale gold metallogenesis in Jiaodong gold- concentrated area is controlled by the uniform geological events, and is identified as an epigenetic mesothermal-epithermal hydrothermal vein gold metallogenic system.

2 Spatio-temporal cluster distributions of

the gold deposits These gold deposits in Jiaodong peninsula

have obvious characteristics of spatio-temporal cluster distribution and lie mainly along the contact zones of different lithofacies around three metamorphic core complexes. From west to east, the gold mineralization age changes from older to newer (Li et al., 2003, 2006; Yang et al., 2014). Therefore, three gold subsystems can be divided, which are the altered rock - quartz vein type in Jiaobei Uplift, the sulfide - quartz vein type in Sulu UHP metamorphic belt and the altered breccia type in north margin of Jiaolai Basin.

The mineralization style changes from disseminated- veinlet, veinlet-stockwork and quartz vein type → sulfide-quartz vein type → altered breccia type. The texture and structure of ores are characterized by veinlet-disseminated structure dominated → band structure and comb structure → breccia structure, indicating that mineralization occurred respectively in the brittle - ductile transformation zone (ca. 15 km deep) → brittle extension-shear fault zone → brittle breccia zone (ca. 5 km deep). The

decrease of the size and strength of alteration and mineralization, and the increase of shallow crustal components in metallogenic materials, may be related to the deposits’ location. This is more and more far away from the source area. The ore-forming P-T conditions gradually decreased and the meteoric water and/or basin to brine ratio in the ore-forming fluids gradually increased (Fan et al., 2003；Hu et al., 2006; Wang et al., 2014b), respectively, which corresponded to the shallower metallogenic depth and more and more elongate-trending mineralizing tectonic environment.

All the regional regular changes of metallogenic characteristics reflect a crustal continuum metallogenic regime in different vertical depth of crust, between the detachment fault ductile – brittle transition zone and the brittle breccia zone.

3 ‘Jiaodong Type’ gold deposit and gold

metallogenic model Mesozoic gold metallogenic system of the

Jiaodong gold province is distinct from typical ‘intrusion-related gold deposit’, ‘orogenic gold deposit’ or other known gold deposit types around the world(Groves et al., 1998; Deng et al., 2014b;Yang et al., 2011), and cannot be classified into the known metallogenic model. To reasonably explain the unique geodynamic background, environment of ore-host rock and mineralization characteristics, we put forward a new interpretation of the ‘Jiaodong type’ gold deposit and ‘Jiaodong type’ gold metallogenic model. We conclude that the retracement of ancient Pacific Izanagi subduction plate may be the main driving mechanism leading to large-scale revitalization of the metallogenic materials in regional Precambrian metamorphic basement rock mass, and the ore-forming fluids mainly came from metamorphic dehydration of subduction plate. Gold is mainly in Au(HS)2

− complex and transported along detachment fault system in ore fluids. The tectonic space as well as the metallogenic temperature increases sharply and pressure decreases suddenly, from around the brittle - ductile transformation zone of detachment fault system to brittle breccia zone. Therefore, CO2 and H2S loss from the ore fluids and sulfofication lead to a stability decrease of Au(HS)2

−and other gold complexes,

161

and the subsequent large-scale gold precipitation and enrichment.

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (Grant No. 41230311), the National Science and Technology Support Program (Grant No.

2011BAB04B09), Geological investigation work project of China Geological Survey (Grant No. 12120114034901), and Open Research Fund Project of State Key laboratory of Geological Processes and Mineral Resources (Grant No.GPMR201307).

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Hu, F.F., Fan, H.R., Zhai, M.G., Jin, C.W., 2006. Fluid evolution in the Rushan lode gold deposit of Jiaodong Peninsula, eastern China. Journal of Geochemical Exploration, 89(1): 161-164.

Li, J.W., Vasconcelos, P.M., Zhang, J., Zhou, M.F., Zhang, X.J., Yang, F.H., 2003. 40Ar/39Ar constraints on a temporal link between gold mineralization, magmatism, and continental margin transtension in the Jiaodong gold province, eastern China. Journal of Geology, 111(6): 741-751.

Li, J.W., Vasconcelos, P.M., Zhou, M.F., Zhao, X.F., Ma, C.Q., 2006. Geochronology of the Pengjiakuang and Rushan gold deposits, eastern Jiaodong gold province, northeastern China: Implications for regional mineralization and geodynamic setting. Economic Geology, 101(6): 1023-1038.

Li, S.R., Santosh, M., 2014.Metallogeny and craton destruction: Records from the North China Craton. Ore Geology Reviews, 56: 376-414.

Tang, J., Zheng, Y.F., Wu, Y.B., Gong, B., Liu, X.M., 2007. Geochronology and Geochemistry of Metamorphic rocks in the Jiaobei terrane: constraints on its tectonic affinity in the Sulu orogen. Precambrian Research, 152(1): 48-82.

Wang, Z.L., 2012. Metallogenic system of Jiaojia gold field, Shandong Province, China. Ph.D. Thesis. Beijing: China University of Geosciences (in Chinese with English

162

abstract). Wang, Z.L., Yang, L.Q., Deng, J., Santosh, M.,

Zhang, H.F., Liu, Y., Li, R.H., Huang, T., Zheng, X.L., Zhao, H., 2014a.Petrogenesis and tectonic setting of gold-hosting high Ba-Sr granitoids in the Xincheng gold deposit, northwest Jiaodong Peninsula, East China: Mineralogy, geochemistry, zircon U-Pb and Lu-Hf isotopes. Journal of Asian Earth Sciences, Doi: http://dx.doi.org/10.1016/j.jseaes.2014.03.001.

Wang, Z.L., Yang, L.Q., Guo, L.N., Marsh, E., Wang, J.P., Liu, Y., Zhang, C., Li, R.H., Zhang, L., Zheng, X.L., and Zhao, H., 2014b. P-T conditions and mechanisms for precipitation of gold in the Xincheng deposit, Jiaodong Peninsula, China: A fluid inclusion study. Ore Geology Reviews, submitted.

Yang, L.Q., Deng, J., Ge, L.S., Wang, Q.F., Zhang, J., Gao, B.F., Jiang, S.Q., Xu, H., 2007. Metallogenic Age and Genesis of Gold Ore Deposits in Jiaodong Peninsula, Eastern China: A Regional Review. Progress in Nature Sciences, 17:138-143.

Yang, L.Q., Deng, J., Guo, C.Y., Zhang, J., Jiang,

S.P., Gao, B.F., Gong, Q.J., and Wang, Q.F., 2009. Ore-Forming Fluid Characteristics of the Dayingezhuang Gold Deposit, Jiaodong Gold Province, China. Resource geology, 59(2): 181-193.

Yang, L.Q., Deng, J., Zhao, K., Liu, J.T., 2011.Tectono- thermochronology and gold mineralization events of orogenic gold deposits in Ailaoshan orogenic belt, Southwest China: Geochronological constraints. Acta Petrologica Sinica, 27(9): 2519-2532(in Chinese with English abstract).

Yang, L.Q., Deng, J., Goldfarb, R.J., Zhang, J., Gao, B.F., Wang, Z.L., 2014. 40Ar/39Ar geochronological constraints on the formation of the Dayingezhuang gold deposit: new implications for timing and duration of hydrothermal activity in the Jiaodong gold province, China. Gondwana Research, 25(4): 1469-1483.

Zhang, L., Liu, Y., Li, R.H., Huang, T., Zhang, R.Z., Chen, B.H., Li, J.K., 2014. Lead isotope geochemistry of Dayingezhuang gold deposit, Jiaodong Peninsula, China. Acta Petrologica Sinica, 30(6) (in Chinese with English abstract).



Abstract Volume


Late Paleozoic ultrahigh-temperature metamorphism of

the Altai orogenic belt of NW China: insight from

pseudosection modelling and fluid inclusion

Xiaoqiang Yang and Zilong Li

Department of Earth Sciences, Zhejiang University, Hangzhou 310027, PR China

Ultrahigh-temperature (UHT) granulite-facies rocks offer important constraints on crustal evolution processes and tectonic history of orogens, particularly for Phanerozoic orogens. Through the study of the Late Paleozoic pelitic UHT granulite from Altai in the western segment of the Central Asian Orogenic Belt (CAOB), the diagnostic mineral in these rocks including high alumina orthopyroxene (Al2O3 up to 9.76 wt.%) coexisting with sillimanite and quartz, and low Zn spinel overgrowth with quartz, and cordierite corona separates sillimanite from orthopyroxene were confirmed. The high alumina orthopyroxene is replaced by symplectites of low-alumina orthopyroxene (5.80 wt.% Al2O3) and cordierite. These textural observations are consistent with a significant decompression following the peak UHT metamorphism. Phase equilibrium modeling using pseudosections and the y(opx) isopleths indicate an anti-clockwise P–T path for the exhumation of the Altai orogenic belt. The pre-peak assemblage of spinel + quartz in garnet is stable at high- to ultrahigh-temperature and low-pressure conditions (P < 5.8 kb at T~900 °C). The peak P–T values recorded by high aluminium orthopyroxene are >940 °C and 7.8-10 kb, and subsequent near-isothermal decompression occurred at 890 to 940 °C and 5-6 kb. The final-stage cooling is recorded during the temperature of 750-800 °C and pressure conditions of 4-5 kb accompanied by a decrease

in the y(opx) values (0.11-0.12). Newly discovered primary and

pseudosecondary fluid inclusions in garnet together with primary fluid inclusions in quartz were studied in terms of petrography and microthermometry as well as laser Raman spectroscopic analyses in detail. Melting temperatures of inclusions obtained indicated that the trapped fluid phase is dominantly carbonic. Raman probe confirmed a near pure CO2 composition with only minor dilutant of N2. The homogenized temperatures of the fluid inclusions both from the quartz in matrix and quartz enclosed in garnet porphyroblasts range from 10.1 °C to 29.0 °C with corresponding density of 0.631-0.865 g/cm3. The range of CO2 isochores computed from density measurements in fluid inclusions passed below the retrograde stage of the P–T trajectory.

We propose that the anti-clockwise P–T path of the UHT granulite in the Altai orogenic belt could be related to an extensional event related to the sinistral strike-slip along the Irtish tectonic belt after the subduction and slab detachment during the convergence of the Kazakhstan-Junggar plate and the Siberian plate. The low-density carbonic fluid inclusions occurring in these rocks are probably the result of density reversal due to the modification of the inclusion cavity volume during rapid decompression. Acknowledgements

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This study was financially supported by the National Basic Research Program of China (973 Program: 2011CB808902), National Natural Science Foundation of China (Grant No.

40972045 and 41072048), and Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110101110001).

References

Yang, X.-Q., Li, Z.-L., 2013. Fluid characteristics of Late Paleozoic ultrahigh-temperature granulites from the Altay orogenic belt, northwestern China and its significance. ActaPetrologicaSinica29, 3446-3456 (in Chinese with English abstract).

Li, Z., Yang, X., Li, Y., Santosh, M., Chen, H., Xiao, W., 2014. Late Paleozoic tectono–metamorphic evolution of the Altai segment of the Central Asian Orogenic Belt: Constraints from metamorphic P–T pseudosection and zircon U–Pb dating of ultra-high-temperature granulite. Lithos.



Abstract Volume


The distribution of Neoproterozoic magmatism during

the breakup of the Rodinia supercontinent: Constraints

from detrital zircon U-Pb ages and Hf isotopes from

Qilian Orogenic Belt and North China Craton

Qingyan Tanga, Mingjie Zhanga, Chusi Lib, Hongfu Zhangc, Ming Yua

a School of Earth Sciences, Lanzhou University, Lanzhou 730000, China

b Department of Geological Sciences, Indiana University, Bloomington, IN 47405, USA c Department of Geology, Northwest University, Xi'an 71000, China;

E-mail: [email protected]

The Neoproterozoic mantle plume had possibly triggered the breakup of the Rodinia supercontinent and large scale basaltic magmatism, which occurred in Tarim, South China Craton and Australia. The age of Jinchuan ultramafic intrusion (Zhang et al., 2010; Li et al., 2005) makes Rodinia breakup magmatism important because of the largest single magmatic Ni-Cu sulfide deposit in the world. In this paper, we use zircon U-Pb dating and Hf isotopes to outline the range of Neoproterozoic mantle plume magmatism possibly related to Ni-Cu sulfide mineralization during the breakup of the Rodinia supercontinent in the Qilian orogenic belt (QOB), Tarim and North and South China Craton (NCC, SCC). 1. Samples and analytical methods

A large lherzolite sample from the Jinchuan intrusion was collected for whole-rock chemistry, zircon U-Pb age and Lu-Hf isotope study. 2 large early-Devonian and Precambrian sandstone samples from the Longshoushan terrane, and 2 Ordovician sandstone and Sinian slate samples from Qilian orogenic belt were used for zircon U-Pb dating and Lu-Hf isotopic study. Zircon crystals in these samples were separated using conventional techniques including magnetic separation, heavy liquids and hand-picking. Zircon U–Pb and Lu-Hf

isotopes were determined in situ using LA-MC-ICP-MS. 2. Results

The comagmatic zircons from the Jinchuan lherzolite give a weighted mean 206Pb/238U age of 821 ± 11 Ma, which is within the range of previously reported zircon U-Pb ages for the Jinchuan intrusion by Li et al. (2005) and Zhang et al. (2010). εHf (t) values vary from -5 to -11. The comagmatic zircon εHf and whole-rock εNd values of the Jinchuan mafic-ultramafic intrusion are between the values of mantle plume and subcontinental lithospheric mantle.

The age distribution of 241 detrital zircons from the early-Devonian and Sinian sandstones with crystallization ages >500 Ma in Longshou-shan is shown in Fig. 1a. The age composition shows major peak ages at 900-1000, 1100-1200, 1400-1500, 1700-2100 and 2400- 2600 Ma. The ɛHf(t) values vary from -20 to +10 (Fig. 2). The U–Pb isotopic compositions of detrital zircons from Qilian show major peak ages at 1400-1500 Ma, as well as 1000-1200, 1700-2100 and 2400-2600 Ma. 3. Discussions

3.1 The distribution of Neoproterozoic magmatism

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The detrital zircons can decipher sedimentary provenances, regional magmatic barcode and crustal evolution. The concordant age distribution patterns of detrital zircons from NCC (Longshoushan, Alxa and Ordos block), Qilian, Tarim and SCC are shown in Fig. 1, and display five peak ages at 700-1000, 1100-1200, 1400- 1500, 1700-2100 and 2400-2600 Ma. Data reveal multistage episodic tectonothermal events related to the assembly and/or breakup of the supercontinents Columbia and Rodinia.

The Alxa Block, where Jinchuan Cu-Ni-PGE deposit occurred, has been traditionally thought of as the westernmost part of NCC and proved by strata comparison, or be considered as derived from SCC during Rodinia breakup based on age relationship (Li et al., 2005). The age spectra in Longshoushan terrane, west of Alxa shows age peaks of 900-1000, 1400-1500, 1700-2100 and 2400-2600 Ma, which is similar to those of Alxa and the nearby Ordos block from NCC, and suggested that Longshou-shan was probably part of the NCC in its early history (Tang et al., 2014).

The Alxa bridged NCC, Tarim, QOB, and SCC. The age distribution patterns of detrital zircons from NCC (Alxa and Ordos), SCC, Tarim and Qilian are all remarkably similar (Fig. 1) in two prominent U–Pb age peaks at 1700-2100 and 2400-2600 Ma, which are consistent with a ∼1.85 Ga and a ∼2.5 Ga magmatic–metamorphic events. The Tarim was considered as a part of the NCC in its early history (Han et al., 2011). Qilian and SCC show

significantly different major age peaks of 1400-1500 Ma and 700-900Ma, respectively, which could be related to Proterozoic supercontinents of Columbia and Rodinia, respectively.

The Neoproterozoic major peak of 700-900 Ma is contemporaneity with Rodinia breakup in a mantle plume system. It is the obviously major peak in West Yangtze (800-850 Ma) and Tarim, and is also the minor peak in Alxa, Ordos and Qilian (Fig.1). Tarim had the same convergent and breakup history of the Rodinia supercontinent as West Yangtze in the Neoproterozoic. Song et al. (2013) argued that Yangtze Block, Qaidam-Qilian Block and Tarim were a “South-West China United Continent” in the Neoproterozoic. The fact that

these all blocks share a common detrital zircon major age peak at 700-1000 Ma indicates that magmatism related to Rodinia breakup is a global event caused by mantle plume.

3.2 The nature of Neoproterozoic magmatism

The breakup duration of the Rodinia supercontinent overlap the age of the Jinchuan intrusion (Zhang et al., 2010). The comagmatic zircon εHf and whole-rock εNd values of the Jinchuan intrusion are between the values of mantle plume and subcontinental lithospheric mantle (Tang et al., 2014), similar to those of plume-related basalts. The contemporaneous Luanchuan gabbros from NCC also show similar values (Wang et al., 2011), suggested that mafic-ultramafic intrusions during the breakup of the Neoproterozoic supercontinent Rodinia are not single event in NCC.

Many mafic-ultramafic intrusions and basalts in West Yangtze (820-840 Ma, Li et al., 1999), Tarim (760Ma) and Qilian (775Ma) were formed during Rodinia breakup. Tongde picritic dike in Yanbian, West Yangtze shows clear rift-related geochemical signatures (796 ± 5 Ma, Li et al., 2010). This rifting event was coupled with subduction, such as the 806 ± 4 Ma Lengshuiqing mafic-ultramafic intrusion (Zhou et al., 2006). Most zircons have positive ɛHf(t) values with mantle signature, some with negative ɛHf(t) values suggested a reworked crustal materials (Fig.2). 4. Conclusions

(1) The 831 Ma mafic-ultramafic intrusion of Jinchuan Cu-Ni sulfide deposit make Rodinia breakup magmatism important.

(2) Detrital zircon data share a common major age peak at 700-1000 Ma in SCC, Tarim, NCC and Qilian, and indicate the global magmatism events

related to Rodinia breakup. This study was supported by NSFC (41372095,

41072056) and SRFDP (20120211110023).

References

Cawood, P.A., Wang, Y., Xu, Y., Zhao, G., 2013. Locating South China in Rodinia and Gondwana? Geology 41, 903-906.

Gehrels, G.E., Yin, A., Wang, X.F., 2003. Detrital zircon geochronology of the northeastern Tibetan Plateau. Geological Society of America Bulletin115, 881-896.

Han, G.Q., Liu, Y., Neubauer, F., Genser, J., Li, W., Zhao,Y., Liang, C., 2011. Origin of terranes in the eastern Central Asian Orogenic Belt, NE China. Tectonophysics, 511(3-4): 109-124.

Li, X.H., Su, L., Chung, S.L., Li, Z.X., Liu, Y., Song, B., Liu, D.Y., 2005. Formation of the Jinchuan ultramafic intrusion and the world’s third largest Ni-Cu sulfide deposit. Geochemistry,

167

Geophysics, Geosystems 6, Q11004, doi: 10.1029/2005GC001006.

Li, X.H., Zhu, W.G., Zhong, H., Wang, X.C., He, D.F., Bai, Z.J., Liu, F., 2010.The Tongde picritic dikes in the Western Yangtze Block. The Journal of Geology118, 509-522.

Li, Z.X., Li, X.H., Kinny, P.D., Wang, J., 1999. The breakup of Rodinia: did it start with a mantle plume beneath South China? Earth and Planetary Science Letters 173, 171-181.

Long, X., Yuan, C., Sun, M., Zhao, G., Xiao, W., Wang, Y., Yang, Y., Hua, A., 2010. Archean crustal evolution of the northern Tarim craton, NW China. Precambrian Research 180, 272-284.

Song, S., Niu, Y., Su, L., Xia, X., 2013. Tectonics of the North Qilian orogen, NW China. Gondwana Research 23, 1378-1401.

Tang, Q.Y., Li, C., Zhang, M.J., Ripley, E., Yu, M., 2014. Locating Alxa and Jinchuan ore-bearing mafic-ultramafic intrusion in Rodinia. Precambrian Research (accepted)

Tung, K., Yang, H.-J., Yang, H.-Y., Liu, D.Y., Zhang, J.X., Wan, Y.S., Tseng, C.-Y., 2007. SHRIMP U-Pb geochronology of the zircons from the Precambrian basement of the Qilian Block and its geological significances. Chinese Science Bulletin52 (19), 2687-2701.

Wang, X.L., Jiang, S.Y., Dai, B.Z., Griffin, W.L., Dai, M.N., Yang, Y.H., 2011. Age, geochemistry and tectonic setting of the

Neoproterozoic (ca 830 Ma) gabbros on the southern margin of the North China Craton. Precambrian Research 190, 35-47.

Wu, G., Sun, J-H., Guo, Q-Y., Tang, T., Chen, Z-Y., Feng, X-J., 2010. The distribution of detrital zircon U-Pb ages and its significance to Precambrian basement in Tarim Basin. Acta Geoscientica Sinica 31: 65-72(in Chinese with English abstract)

Zhang, J., Li, J., Liu, J., Feng, Q., 2011. Detrital zircon U–Pb ages of Middle Ordovician flysch sandstones in the western Ordos margin. Journal of Asian Earth Sciences 42, 1030-1047.

Zhang, M., Kamo, S.L., Li, C., Hu, P., Ripley, E.M., 2010. Precise U-Pb zircon- baddeleyite age of

the Jinchuan sulfide ore-bearing ultramafic intrusion, western China. Mineralium Deposita 45, 3-9.

Zhou, M.-F., Ma, Y., Yan, D.-P., Xia, X., Zhao, J.-H., Sun, M., 2006. The Yanbian terrane (southern Sichuan province, SW China).

Precambrian Research 144, 19-38.

Fig. 1 Detrital zircon age distributions for sedimentary rocks from Alxa, Ordos, Qilian and Western Yangtze (n, total

number of analyses). Sources of data are from Gehrel et al. (2003); Tung et al. (2007); Wu et al. (2009); Zhang et al.

(2011); Carroll et al. (2013) and Tang et al. (2014) with reference.

Fig. 2 εHf versus U–Pb crystallisation ages for sedimentary rocks from Longshoushan, Alxa, North China Craton, West Yangtze and Tarim. Sources of data are from Long et al. (2010) and Tang et al. (2014) with reference.



Abstract Volume


Paleoproterozoic arc magmatism in the North China

Craton: Geochemical, and zircon U-Pb and Lu-Hf

constraints

Qiong-Yan Yang*, M. Santosh

School of Earth Sciences and Resources, China University of Geosciences, 29 Xueyuan Road, Beijing

100083, China *Corresponding author e-mail: [email protected]

Following major crust building and amalgamation of microblocks during Neoarchean, the North China Craton witnessed a prolonged subduction-accretion process during Paleoproterozoic culminating in the final collisional of the crustal blocks into a coherent tectonic framework in late Paleoproterozoic (Zhai and Santosh, 2011; Zhao and Zhai, 2013). Evidence for Paleoproterozoic subduction-accretion history is well preserved in several segments along the two major collisional sutures of the North China Craton (e.g., Santosh et al., 2013; Yang et al., 2014), the E-W trending Inner Mongolia Suture Zone (IMSZ, Santosh, 2010; also incorporating the Khondalite Belt; Zhao et al., 2005) and the approximately N-S trending Trans-North China Orogen (TNCO; Zhao et al., 2005). Here we report a suite of arc magmatic rocks including granitoids, gabbro-diorite, volcanic tuff as well as granulite facies metapelites (khondalite) from the Inner Mongolia region of the North China Craton and present their petrologic, geochemical and zircon U-Pb and Lu-Hf characteristics. The magmatic suite ranges in chemistry from calc-alkaline to shoshonitic affinity. The meta-tuff, meta-granite and khondalite show rhyolite-dacite composition. The charnockite and gabbroic suite shows metaluminous calc-alkaline affinity

whereas the granitoids, tuff and khondalite have peraluminous composition. The entire magmatic suite shows volcanic-arc signature with subduction-dominated chemical features. Their primitive mantle-normalized trace element distribution patterns display enrichment in large ion lithophile elements (LILE) relative to high field strength elements (HFSE) and negative Nb-Ta, Zr-Hf anomalies attesting to a subduction-related origin. The LILE and LREE enrichment and relative HFSE depletion might suggest dehydration of subducted oceanic lithosphere and influx of fluid mobile elements into the mantle wedge through metasomatic processes. The REE fractionation trends and a large variation in Y contents of the magmatic suite depict a heterogeneous source marked by subduction-derived arc components with minor input from continental crust. The geochemical features of the magmatic suite are consistent with their derivation in a continental arc related to an active margin.

Zircon U-Pb analyses yield 207Pb/206Pb weighted mean ages of 2410±41 Ma for the metagranite; 2480±12 to 2125±18 Ma for the metagabbro; 24446±11 Ma for charnockite; and 1904±6 to 1901±9 Ma for metatuff. The metamorphic zircons in the various rocks including the khondalite yield ages in the range


170

of 1890±14 to 1852±19 Ma. The age data suggests prolonged arc magmatism in a convergent margin setting during ca. 2.48 to 1.9 Ga, followed by metamorphism at ca. 1.89-1.85 Ga associated with the final collision. Lu-Hf analyses reveal that the dominant populations of zircons from all the rock types are characterized

–1.9 to 6.8; mean 1.8)

DMC data suggest

that the magmas were mostly derived from Neoarchean and Paleoproterozoic juvenile components. We integrate the results from this study to propose major Paleoproterozoic arc magmatic events in the North China Craton associated with the final assembly of the crustal blocks into a coherent craton.

Fig. 1 Hf versus 207Pb/206Pb age plots for zircons from the rocks analyzed in the present study.

References

Santosh, M., 2010. Assembling North China Craton within the Columbia supercontinent: the role of double-sided subduction. Precambrian Research 178, 149–167.

Santosh, M., Liu, D., Shi, Y., Liu, S.J., 2013. Paleoproterozoic accretionary orogenesis in the North China Craton: A SHRIMP zircon study. Precambrian Research 227, 29-54.

Yang, Q.Y., Santosh, M., Tsunogae, T., 2014a. First report of Paleoproterozoic incipient charnockite from the North China Craton: implications for ultrahigh-temperature metasomatism. Precambrian Research 243, 168-180.

Zhai, M.G., Santosh, M., 2011. The early Precambrian odyssey of North China Craton:

a synoptic overview. Gondwana Research 20, 6–25.

Zhao, G.C., Sun, M., Wilde, S.A., Li, S.Z., 2005. Late Archean to Paleoproterozoic evolution of the North China Craton: key issues revisited. Precambrian Research 136, 177–202.

Zhao, G.C., Zhai, M.G., 2013. Lithotectonic

elements of Precambrian basement in the North China Craton: Review and tectonic implications. Gondwana Research 23, 1207-1240.



Abstract Volume


Inclusions of α-quartz, albite and olivine in a mantle

diamond

Zuowei Yina,*, M. Santoshb, Cui Jiang3, Qinwen Zhua, Fengxiang Lub

aGemological Institute, China University of Geosciences, Wuhan, 430074, P.R. China

bSchool of Earth Sciences and Resources, China University of Geosciences, 29 Xueyuan Road, Beijing

100083, P.R. China

cSchool of Foreign Language, China University of Geosciences, Wuhan, 430074, P.R. China *Corresponding author e-mail: [email protected]

Mineral inclusions in diamonds have been used to track potential information on the Earth’s deep mantle. Here we report results from a detailed study on the mineral inclusions in a ca. 0.28 ct diamond from the Shengli No.1 kimberlite in Mengyin County, Shandong Province, eastern China. Our study reveals the

presence of α-quartz, albite and olivine in the diamond. With an inferred depth of ca. 165 km for the diamond crystallization, the inclusions of α- quartz and albite suggest the possible involvement of deep subducted crustal material, traces of which were captured during the diamond growth and magma migration.




Abstract Volume


Japanese student Himalayan exercise program

Masaru Yoshidaa,b,, Kazunori Aritac, Tetsuya Sakaid, Bishal Nath Upretib

aGondwana Institute for Geology and Environment, Hashimoto 648-0091, Japan bDepartment of Geology, Tri-Chandra Campus, Tribhuvan University, Kathmandu, Nepal cGeneral Science Museum, Hokkaido University, Sapporo 060-0810, Japan

dDepartment of Natural Resources and Environment, Shimane University, Matsue 690-8504, Japan *Corresponding author e-mail: [email protected]

The Japanese Student Himalayan Exercise Program started in 2010 and the exercise tours have been conducted every year since March 2012. The tour was conducted by one team which was composed generally of less than 20 Japanese and 2 Nepalese students, associated with two–three Japanese and Nepalese teachers. One of the Japanese teachers works as the team leader.

The tour course follows the route Kathmandu – Pokhara – Jomsom – Muktinath – Jomsom – Pokhara – Tansen – Lumbini – Mugling – Kathmandu, crossing all the geotectonic zones of the Himalayan Orogen extending from the Tethys Himalaya to Indo-Gangetic Plain (Fig. 1), and chartered vehicles are used all through the tour. A geo-excursion guidebook along the upper reaches of the Kaligandaki Valley and surrounding Pokhara (Upreti and Yoshida, 2005) has been utilized as the textbook of the exercise tour. The duration of the tour is nine days attached with three days of seminars and city tours, and several

tens of Nepalese students joined all the seminars and city tours.

The program has been advertised throughout Japan, to about 60 geoscience departments of universities, and participants so far included 40 students from 9 Japanese universities and 1 Nepalese university. The tour has been organized fully by voluntary work of the Student Himalayan Exercise Project composed of four Japanese and Nepalese geologists so that students would be able to join the tour with minimal expenses. Thirty Japanese and Nepalese teachers have registered as candidate teachers for the exercise tour. The program encouraged participants to not only understand and to become familiar with the Himalayan geology but also to get expertise in field geology. Further, students were also encouraged to become familiar with English, thereby also increasing their internationality.

In the presentation, the outline of the result of the March 2014 tour will be demonstrated.


173

Fig. 1 Geological outline of the geo-exercise area with the tour course and night halts (encircled numbers). The base geologic map is modified after the Department of Mines and Geology, 1982.

References

Department of Mines and Geology, 1982,

Geological Map of Nepal, 1:100,000. HMG Ministry of Industry, Department of Mines and Geology, Nepal.

Upreti, B.N. and Yoshida, M., 2005,

Guidebook for Himalayan Trekkers, Ser. 1, Geology and Natural Hazards along the Kaligandaki Valley, Nepal. Special Publication No. 1, Department of Geology, Tri-Chandra Campus, Tribhuvan University. Kathmandu, 165 pages.



Abstract Volume


The Anarak Metamorphic Complex (central Iran) and its

significance for the Cimmerian orogeny

Stefano Zanchettaa, Andrea Zanchia, Nadia Malaspinaa, Fabrizio Berraa, Maria

Aldina Bergomia

aDepartment of Earth and Environmental Sciences, University of Milano Bicocca, Piazza della Scienza

1, 20126 Milano, Italy ([email protected]) b Department of Earth Sciences, University of Milano, via Botticelli 23, 20133 Milano, Italy

The Cimmerian orogeny shaped the southern margin of Eurasia during the Late Permian and the Triassic. Several microplates, detached from Gondwana in the Early Permian, migrated northward to be accreted to the Eurasian margin. In the reconstruction of such orogenic events Iran is a key area. The occurrence of several ‘ophiolite’ belts of various ages, from the Paleozoic to the Cretaceous, poses several questions on the possibility that a single rather than multiple Paleotethys sutures occur between Eurasia and Iran.

In this scenario the Anarak region in Central Iran still represents a conundrum. Contrasting geochronological, paleontological, paleomagnetic data and reported field evidence suggest different origins for the Anarak Metamorphic Complex (AMC). The AMC is either interpreted to be part of the microplate of Gondwanan affinity, a relic of an accretionary wedge developed at the Eurasian margin during the Paleotethys subduction or part of the Cimmerian suture zone, occurring in NE Iran, displaced to central Iran by counterclockwise rotation of the central Iranian blocks from the Triassic.

Our field structural data, petrographic and geochemical data, carried out in the frame of the DARIUS PROGRAMME, indicate that the AMC is not a single coherent block, but consists

of several units (Morghab, Chah Gorbeh, Patyar, Palhavand Gneiss, Lakh Marble, Doshak and dismembered ‘ophiolites’) which display different tectonometamorphic evolutions. The Morghab and Chah Gorbeh units share a common history and they preserve, as a peculiar feature within metabasites, a prograde metamorphism with syn- to post-deformational growth of blueschist facies assemblages on pre-existing greenschist facies mineralogical associations. LT-HP metamorphism responsible for the growth of sodic amphibole has also been recognized within the marble lenses at the southern limit of the Chah Gorbeh unit. Finally, evidence of LT-HP metamorphism also occurs in the metabasites and possibly also in the serpentinites that form most of the ‘ophiolites’ within the AMC. Structural analyses show that the Chah Gorbeh, Morghab units and the ‘ophiolites’ have been tectonically coupled during at least two deformational phases that occurred at greenschist facies conditions and predate the LT-HP metamorphic overprint. Available geochronological data loosely constraints the subduction event in the Late Permian–Early Triassic times. Subsequent deformation events that occurred during the whole Mesozoic and the Cenozoic up to the Miocene and possibly later, resulted in folding, thrusting and faulting that dismembered the

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original tectonic contacts. Therefore, the correlations among deformation structures and metamorphic events in the different units are not straightforward.

The other units of the AMC lack evidence of HP metamorphism, especially the Lakh Marble, a large thrust sheet that occupies the uppermost structural position in the AMC. The contact with the underlying units is invariably tectonic, thus no original relationships have been preserved.

So, if structural and petrographic data point to an accretionary wedge setting for the evolution of the Chah Gorbeh, Morghab and the ‘ophiolites’, geodynamic significance and paleogeographic attribution of other units still remain controversial. In progress is the work on U-Pb dating of undeformed intrusive bodies and metamorphic minerals in the LT-HP rocks, results of which will soon help to better constrain the evolution of the ACM.



Abstract Volume


Nature of the source rocks from the Delingha paragneiss

suites, NW China and implications for Precambrian

tectonics

L. Zhanga, Q. Y. Wanga, N. S. Chena,b*, M. Sunb, M. Santoshc, J. Bad

aFaculty of Earth Science, China University of Geosciences, Wuhan 430074, China bDepartment of Earth Sciences, The University of Hong Kong, Hong Kong SAR, China cJournal Center, China University of Geosciences Beijing, 100083, China dInstitute of Geological Survey, Sichuan Province, Chengdu 610081, China

*Corresponding author e-mail: [email protected]

The Delingha paragneiss suite in the Quanji massif, southeastern Tarim Craton, is composed of mica schist, paragneiss, leptynite and quartzite, similar to the ‘khondalite suites’ described from elsewhere in the world (Walker, 1902; Cooray, 1960; Barbey and Cuney, 1982; Walton et al., 1983; Chacko et al., 1987; Dash et al., 1987; Santosh, 1987; Lu et al., 1996). The mica schist is rich in Al2O3 (up to ~26 wt%) and contains graphite and diagnostic minerals including sillimanite and garnet, with metamorphism under amphibolite-facies to locally granulite-facies conditions as manifested by association with amphibolite and granulite (Chen et al., 2013; Zhang et al., 2001). The detrital zircon U-Pb ages and geochemical data indicate that the protolith materials of the Delingha paragneiss suite were mainly sourced from 2.20–2.45 Ga granites, felsic volcanic rocks and TTG (Figure 1), and were deposited at 2.17–1.92 Ga (Huang et al., 2011; Chen et al., 2012; Zhang et al., 2014). The detrital zircon Hf and whole-rock Nd isotopes document important crustal growth at ~2.5–2.7 Ga (Chen et al., 2012; Zhang et al., 2014). The detrital zircon age spectra, the whole rock Nd and zircon Hf model ages, the low-maturity of the protolith, and

short-distance transportation suggest that the detritus were derived from the underlying Delingha Complex and the lower Dakendaban sub-Group (Chen et al., 2012; Zhang et al., 2014). The timing of magmatic activities in the source region, the depositional age and metamorphic histories of the Delingha paragneiss suite are all comparable to those recorded in the khondalite belt along northern margin of the Ordos Block in the North China Craton (Condie et al., 1992; Lu et al., 1996). Our study shows that the 2.2–2.45 Ga magmatic rocks were generated in arc or active continental margin settings (Zhang et al., 2014), suggesting a prolonged subduction and accretion history prior to final amalgamation (~2.5 –1.8 Ga) to form the unified North China Craton and the assembly of the Tarim Craton in NW China (Zhao et al., 2005; Santosh, 2010; Santosh et al., 2010, 2013; Liao et al., 2014). Acknowledgements

This study was supported by the National Science Foundation of China, NSFC grants (Nos. 41172069, 41372075, 40972042 and 41273048) and a HKU CRCG Grant. This study is a contribution to the 1000 Talents Award to M. Santosh from the Chinese Government and to the Joint Laboratory of Chemical Geodynamics


177

between HKU and CAS (Guangzhou Institute of Geochemistry).

Fig. 1 Discrimination diagrams for tectonic setting affinity (a) (after Floyd and Leveridge. 1987) and compositions (b-d) of the source rocks (after Kontinen et al., 2007) for the protolith deposits of the Delingha khondalite (after Zhang et al., 2014).

References

Barbey, P. and Cuney, M., 1982. K, Rb, Sr, Ba, U and The geochemistry of the Lapland granulites (Fennoscandia). LILE fractionation controlling factors. Contributions to Mineralogy and Petrology 81, 304- 316.

Chacko, T., Kumar, G.R.R., Newton, R.C., 1987. Metamorphic PT conditions of the Kerala (south India) Khondalite Belt, a granulite facies supracrustal terrain. The Journal of Geology 95, 343–358.

Chen, N.S., Liao, F.X., Wang, L., Santosh, M., Sun, M., Wang, Q.Y., Hassan, A.M., 2013. Late Paleoproterozoic multiple metamorphic events in the Quanji Massif: Links with Tarim and North China Cratons and implications for assembly of the Columbia supercontinent. Precambrian Research 228, 102–116.

Chen, N.S., Zhang, L., Sun, M., Wang, Q.Y., Kusky, T.M., 2012. U- Pb and Hf isotopic compositions of detrital zircons from the paragneisses of the Quanji Massif, NW China: Implications for its early tectonic evolutionary history. Journal of Asian Earth Sciences 55, 110–130.

Condie, K.C., Boryta, M.D., Liu, J.Z., Qian, X.L.,

1992. The origin of khondalites: geochemical evidence from the Archean to Early Proterozoic granulite belt in the North China Craton. Precambrian Research 59, 207–223.

Cooray, P. G., 1960. Khondalites and charnockites

of the Lagalla–Pallegamma area, Ceylon. Bull. Mysore Geologists' Association 18, 117–166.

Dash, B., Sahu, K.N. Bowes, D.R., 1987. Geochemistry and original nature of Precambrian khondalites in the Eastern Ghats, Orissa, India. Transactions of the Royal Society of Edinburgh 78, 115–127.

Floyd, P.A., Leveridge, B.E., 1987. Tectonic environment of the Devonian Gramscatho basin, south Cornwall: framework mode and geochemical evidence from turbiditic sandstones. Journal of the Geological Society 144, 531–542.

Kontinen, A., Käpyaho, A., Hunnu, H., Karhu, J., Matukov, D.I., Larionov, A., Sergeev, S.A., 2007. Nurmes paragneisses in eastern Finland, Karekian craton: Provenance, tectonic setting and implications for Neoarchaean craton correlation. Precambrian Research 152, 119–148.

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Liao, F.X., Zhang, L., Chen, N.S., Sun, M., Santosh, M., Wang, Q.Y., Hassan, A.M., 2014. Geochronology and geochemistry of meta–mafic dykes in the Quanji Massif, NW China: Paleoproterozoic evolution of the Tarim Craton and implications on the assembly of the Columbia supercontinent. Precambrian Research 249, 33–56.

Lu, L.Z., Xu, X.C., Liu, F.L., 1996. Early Precambrian Khondalite series of North China. Changchun Publishing House, Changchun. pp. 1–272 (in Chinese).

Santosh, M., 1987. Cordierite gneisses of Southern Kerala, India: petrology, fluid inclusions and implications for crustal uplift history. Contributions to Mineralogy and Petrology 96, 343–356.

Santosh, M., 2010. Assembling North China Craton within the Columbia supercontinent: The role of double–sided subduction. Precambrian Research 178, 149–167.

Santosh, M., Liu, D.Y., Shi, Y.R., Liu, S.J., 2013. Paleoproterozoic accretionary orogenesis in the North China Craton: A SHRIMP zircon study. Precambrian Research 227, 29–54.

Walker, T.L., 1902. The geology of Kalahandi State, Central Province. Memoirs of the Geological survey of India 33, 1–22.

Walton, E.K., Randall, B.A.O., Battey, M.H. and Tornkeieff, O., 1983. Dictionary of Petrology. John Wiley and Sons.

Zhang, J.X., Wan, Y.S., Xu, Z.Q., Yang, J.S., Meng, F.C. 2001. Discovery of basic granulite and its formation age in Delingha area, North Qaidam Mountains. Acta Petrologica Sinica 17, 453–458 (in Chinese with English abstract).

Zhang, L., Qin, Y. W., Chen, N.S., Sun, M., Santosh, M., Ba, J., 2014. Geochemistry and detrital zircon U-Pb and Hf isotopes of the paragneiss suite from the Quanji massif, SE Tarim Craton: implications for Paleoproterozoic tectonics in NW China. Journal of Asian Earth Sciences, DOI. 10.1016/j.jseaes.2014.05.014

Zhao, G.C., Sun, M., Wilde, S.A., Li, S.Z., 2005. Late Archean to Paleoproterozoic evolution of the North China Craton: key issues revisited. Precambrian Research 136, 177–202.



Abstract Volume


S–Pb isotopic geochemical constraints on the origin of

the Dayingezhuang gold deposit, Jiaodong Peninsula,

China

Liang Zhanga, Liqiang Yanga*, Zhongliang Wanga, Linnan Guoa, Yue Liua, Ruihong

Lia, Tao Huanga and Ruizhong Zhanga, a

aState Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences,

Beijing 100083, China bZhaojin Mining industry Co., LTD., Zhaoyuan 265400, Shandong, China *Corresponding author e-mail: [email protected]

1. Introduction The Jiaodong Peninsula, located in

southeast North China Craton (Deng et al., 2009), defines the China's largest gold province with proved reserves of 4000 t Au (Goldfarb and Santosh, 2014; Yang et al., 2014a). Dayingezhuang gold deposit, a typical Jiaojia-style gold deposit, is located in the center of the Zhaoping Fault zone, northwest Jiaodong Peninsula (Deng et al., 2011). The gold ore bodies occur in pyrite-sericite-quartz altered zone, controlled by the major NNE-trending Zhaoping Fault. Garnet-biotite schist, biotite-plagioclase granulite and plagioclase amphibolite of Jiaodong Group, and the Linglong biotite granite comprise the hanging wall and footwall rocks of Zhaoping fault respectively. Generally, the ore is composed of quartz, sericite, plagioclase, K-feldspar, pyrite, chalcopyrite, galena, sphalerite, and traces of gold and electrum. The gold bearing minerals include pyrite, quartz, and traces of galena and sphalerite. Hydrothermal sericite and muscovite from the Dayingezhuang deposit yield 40Ar/39Ar plateau age of 130±4 Ma (Yang et al., 2013, 2014b). δD-δ18O isotope suggests that ore

forming fluids were derived from magmatic fluids (Yang et al., 2009).

Sulfur and lead isotopes are commonly used in tracing the source of the metallogenic elements in hydrothermal gold deposits (e.g. Li et al., 2012; Zhang et al., 2014). Therefore, S and the Pb isotopic geochemistry were studied to constrain the origin of the Dayingezhuang gold deposit. 2. S-Pb isotopic geochemistry

Twenty δ34SV-CDT values for pyrite, galena and sphalerite samples from the Dayingezhuang gold deposit range from +4.58‰ to +7.54‰, mainly between +6.00‰ to +7.54‰ with an average of +6.71‰. The 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb values of twelve pyrite, two galena and one sphalerite samples are in the ranges of 17.2157-17.3585, 15.4595-15.6116 and 37.858-38.3328, respectively. The distribution of sulfur and lead isotopic compositions from pyrite, galena and sphalerite in the Dayingezhuang gold deposit exhibits a generally concentrated field, indicating that these sulfides have homogeneous lead isotopes and may be derived from the same metallic source. Twenty-eight δ34SV-CDT values for ore-bearing Linglong biotite granite range

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from +3.30‰ to +15.00‰ (Yang et al., 2014a). Six feldspar and four whole rock samples yield 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb of 17.3010-17.4940, 15.4040-17.4740 and 37.5870-38.0430, respectively (Li and Yang, 1993). The sulfide and biotite granite samples are homogeneous in both S and Pb isotope compositions, which suggests that metallogenic elements may be derived from the host granites. The ore-bearing Linglong biotite granite was derived by partial melting of Neoarchean lower-crustal rocks (Hou et al., 2007). The granites inherited the main isotopic characteristics of the Neoarchean lower-crustal rocks, metamorphic basement rocks of Jiaodong Group (Li and Yang, 1993). Furthermore, the original Archaean rocks are largely composed of Trondhjemite-Tonalite-Granodiorite (TTG) and basaltic volcanic rocks

(Jahn et al., 2008), which have a high content of gold. Therefore, the metallogenic elements may be derived from the Neoarchean lower-crustal rocks. Acknowledgements

Thanks are given to Prof. Jun Deng for the significant comments on this manuscript. This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 41230311), the National Science and Technology Support Program (Grant No. 2011BAB04B09), the Geological investigation work project of China Geological Survey (Grant no. 12120114034901), and Open Research Fund Project of State Key laboratory of Geological Processes and Mineral Resources (Grant No. GPMR201307).

References

Deng, J., Wang, Q.F., Wan, L., Liu, H., Yang, L.Q., Zhang, J., 2011. A multifractal analysis of mineralization characteristics of the Dayingezhuang disseminated-veinlet gold deposit in the Jiaodong gold province of China. Ore Geology Reviews 40: 54-64.

Deng, J., Wang, Q.F., Wan, L., Yang, L.Q., Gong, Q.J., Zhao, J., Liu, H., 2009. Self-similar fractal analysis of gold mineralization of Dayingezhuang disseminated- veinlet deposit in Jiaodong gold province, China. Journal of Geochemical Exploration 102: 95-102.

Goldfarb, R.J., Santosh, M., 2014. The dilemma of the Jiaodong gold deposits: Are they unique? Geoscience Frontiers 5: 139-153.

Hou, M.L., Jiang, Y.H., Jiang, S.Y., Ling, H.F. Zhao, K.D., 2007. Contrasting origins of late Mesozoic adakitic granitoids from the northwestern Jiaodong Peninsula, East China: Implications for crustal thickening to delamination. Geological Magazine 144: 619-631.

Jahn, B.M., Liu, D.Y., Wan, Y.S., Song, B., Wu, J.S., 2008. Archean crustal evolution of

the Jiaodong Peninsula, China, as revealed by zircon SHRIMP geochronology, elemental and Nd-isotope geochemistry. American Journal of Science 308: 232-269.

Li, N., Yang, L.Q., Zhang, C., Zhang, J., Lei, S.B., Wang, H.T., Wang, H.W., Gao, X., 2012. Sulfur isotope characteristics of the Yangshan

gold belt, West Qinling: Constraints on ore-forming environment and material source. Acta Petrologica Sinica 28: 1577-1587.

Li, Z.L., Yang, M.Z., 1993. The Geology–Geochemistry of Gold Deposits in Jiaodong Region. Science and Technology Press, Tianjin 1–293 (in Chinese with English abstract).

Yang, L.Q., Deng, J., Wang, Z.L., Zhang, L., Guo, L.N., Song, M.C., Zheng, X.L., 2014a. Mesozoic gold metallogenic system of the Jiaodong gold province, eastern China. Acta Petrologica Sinica 30 (in Chinese with English abstract).

Yang, L.Q., Deng, J., Goldfarb, R.J., Zhang, J., Gao, B.F., Wang, Z.L., 2014b. 40Ar/39Ar geochronological constraints on the formation of the Dayingezhuang gold deposit: new implications for timing and duration of hydrothermal activity in the Jiaodong gold province, China. Gondwana Research 25: 1469-1483.

Yang, L.Q., Deng, J., Goldfarb, R.J., Zhang, J., Wang, Z.L., 2013. Timing and duration of

hydrothermal activity and geochronological constraints on the formation of the Dayingezhuang gold deposit, Jiaodong gold province, China. Geological Journal of China University 19: 400 (in Chinese).

Yang, L.Q., Deng, J., Guo, C.Y., Zhang, J., Jiang, S.Q., Gao, B.F., Gong, Q.J., Wang, Q.F., 2009.

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Ore-forming fluid characteristics of the Dayingezhuang gold deposit, Jiaodong gold province, China. Resource geology 59: 181-193.

Zhang, L., Liu, Y., Li, R.H., Huang, T., Zhang,

R.Z., Chen, B.H., Li, J.K., 2014. Lead isotope geochemistry of Dayingezhuang gold deposit, Jiaodong Peninsula, China. Acta Petrologica Sinica, 30 (in Chinese with English abstract).



Abstract Volume


Behaviors of crust and upper mantle of Indian continent

beneath western Tibet

Junmeng Zhaoa, Robert D. van der Hilstb*, Qian Xua, Huajian Yaob, Hongbing Liua,

Shunping Peia Ling Baia

aKey Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research,

Chinese Academy of Sciences, Beijing 100085, China; bMassachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307

Surface wave tomography is a useful tool in imaging earth's crust and uppermost mantle on both regional and global scales. The high-frequency surface wave dispersion measurements have been used in constraining the structure of the crust and uppermost upper mantle of the Tibetan Plateau even though it is extremely difficult to obtain from seismic events, due to scattering and attenuation. Seismic ambient noise is rich in high-frequency surface waves. Using these surface waves we have extracted Empirical Green's Functions between pairs of stations by cross-correlating long noise

sequences. Based on surface wave dispersion obtained from the empirical Green's functions the tomography has been carried out to obtain high-resolution, short-period (6-30 s) surface wave dispersion of the Earth in both regional and continental scales. This study applies the ambient noise tomography method to the seismic data of ANTILOPE-I located in the western Tibet, using temporary broad-band deployments. With these results, combined with those by P and S receiver function along the same profile, we propose a geodynamic model for the western Tibet.



Abstract Volume


Preliminary paleomagnetic results of the 925 Ma mafic

dykes from the North China Craton: implications for the

Neoproterozoic paleogeography of Rodinia

Xixi Zhaoa,b,*, Peng Pengc, Xinping Wangc, and Yun Lic

aState Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China, bInstitute of Geophysics and Planetary Physics, University of California, Santa Cruz, California 95064,

USA cState Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy

of Sciences, Beijing 100029, China. *Corresponding author e-mail: [email protected]

Precambrian mafic dyke swarms are useful geologic records for Neoproterozoic paleogeographic reconstruction as they may have been emplaced parallel to Precambrian continental margins or radiated out from a common magmatic center where continental breakup may ultimately take place. Precambrian mafic dyke swarms occurred within the accuracy of isotopic dating—at 925 Ma in North China Craton (NCC) and at the same time in São Francisco Craton (SFC), Brazil. These coeval dyke swarms set the stage for postulating an adjacent position of these cratons in the Neoproterozoic. We present a paleomagnetic study of the 925 Ma Dashigou dyke swarm from three widely separated locations in the central and northern parts of the North China Craton. We collected oriented paleomagnetic samples from a total of 17 sites in these previously unsampled regions. Stepwise thermal and alternating field demagnetizations were successful in isolating two magnetic components. The lower unblocking temperature component

represents the recent Earth magnetic field. The higher unblocking temperature component is the characteristic remanent magnetization and yields positive baked contact test. One mafic dyke site also has reversed polarity direction, indicating that paleosecular variation may have been averaged out and there was no regional event that has reset the remanent magnetization of all the dyke sites. The similarity of the site mean directions and virtual paleomagnetic poles for the three sampled regions also argues that the characteristic remanent magnetizations are primary magnetizations that occurred when the dykes were emplaced. The paleomagnetic poles from the Dashigou dyke swarm of the NCC are not similar to those of the identically aged Bahia dykes from SFC, Brazil, indicating that these mafic dykes are not part of a common regional magmatic event that affected North China Craton and NE Brazil at about 925 Ma. The preliminary paleomagnetic results suggest that NCC and SFC were probably not genetically related cratons in the Neoproterozoic.




Abstract Volume


Hidden magmatism revealed by post-collisional

magmatism in Lhasa terrane, Tibet

Zhidan Zhaoa,*, Di-Cheng Zhua, Dong Liua, Xuanxue Moa, Don DePaolob, Yaoling

Niua, c

aState Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and

Resources, China University of Geosciences, Beijing 100083, China bCenter for Isotope Geochemistry, University of California, Berkeley, CA 94720, USA cDepartment of Earth Sciences, Durham University, Durham DH1 3LE, UK *Corresponding author e-mail: [email protected]

The postcollisional potassic and ultrapotassic magmatism in western Lhasa terrane has been well-studied in the past decade. Among them, the 21-25 Ma magmatism has been recognized by Ar-Ar dating in Shiquanhe, Xiongba, Bangba and Wenbu areas. Here, for the first time, we present our new zircon LA-ICPMS U-Pb dating and Hf isotope data on new potassic outcrops in Xiongba and Bangba areas of western Lhasa terrane, to further constrain their age and the nature of their source regions. These rocks are high-K calc-alkaline dacite and shoshonitic trachyte, with SiO2 content ranging from 63 to 69%, MgO from 0.6 to 2.5%, and K2O/Na2O from 1.5 to 6.2%.

One hundred zircon grains from seven potassic samples in Xiongba and Bangba give concordant LA-ICPMS U-Pb ages of 23-24 Ma. These 100 zircon grains yield 176Hf/177Hf ratios ranging from 0.282273 to 0.282531, corresponding to εHf (t) values of –17.1 to –8.0. Their Hf depleted-mantle modal ages (TDM) and crustal model ages (TDM

C) are in the range of 1.0–1.4 Ga, and 1.6–2.2 Ga, respectively. This type of zircon has δ18O ranging from 9.6 to 12.3 in sample XB0801. This suggests that the rocks are derived mainly from a source region with significant contributions from mature crustal materials.

We also found two major clusters of inherited zircons with concordant U-Pb ages in the potassic rocks. The first (39 zircon grains) yields a peak age

of ~90 Ma (MSWD = 2.0), with positive εHf (t) values ranging from ~0 to 6. Such zircon εHf (t) values are significantly lower than those of the contemporaneous granite (86.4 Ma) near Quxu in central Gangdese batholith (εHf = 10–13, Ji et al., 2009). This implies that the ~90 Ma magmatism with contributions from depleted mantle materials also exists in the western Lhasa terrane, but outcrops are yet to be recognized. The second cluster (10 zircon grains) yields a peak age of ~152 Ma, with negative εHf (t) values of –11 to –5.2, and oxygen isotopes (δ18O) ranging from 6.7 to 9.5, suggesting the presence of Late Jurassic magmatism in the same area. Contemporaneous granitic magmatism (152 and 159 Ma) with different εHf (t) values (10–15) was recently reported in Dazhuqu, central Gangdese batholith by Ji et al. (2009).

Our preliminary results reveal that the ~90 Ma and ~152 Ma magmatic events with source regions different from the central Gangdese batholiths probably are volumetrically significant in the western Lhasa terrane. We interpret the hidden ~90 Ma magmatism as having been generated by partial melting of the lower crust, while the ~152 Ma magmatism was derived largely from anatexis or remelting of middle–upper crust with mature continental materials beneath the western Lhasa terrane.




Abstract Volume


A magmatic approach to date the India–Asia collision

Di-Cheng Zhua*, Qing Wanga, Zhi-Dan Zhaoa, Sun-Lin Chungb, Peter A. Cawoodc,

Yaoling Niud, Sheng-Ao Liua, Fu-Yuan Wue, Xuan-Xue Moa

aState Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and

Resources, China University of Geosciences, Beijing 100083, China bDepartment of Geosciences, National Taiwan University, Taipei 10617, Taiwan cDepartment of Earth Sciences, University of St Andrews, North Street, St Andrews KY16 9AL, UK dDepartment of Earth Sciences, Durham University, Durham DH1 3LE, UK eInstitute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China *Corresponding author e-mail: [email protected]

The role of petrological and geochemical data in identifying collisional processes is ambiguous. Here we present a magmatic approach to date the India–Asia collisional processes. A significant flare up in intensity of magmatic activity (including ignimbrite and mafic rock) at ca. 5251 Ma along the Gangdese arc in southern Tibet corresponds with a sudden drop in the India–Asia convergence rate. Magmatism during 8040 Ma in the arc migrates from south to north and then back to south and is characterized by significant mantle input at

7043 Ma. Geological and geochemical data indicate that the mantle input is controlled by slab rollback from ca. 70 Ma, and slab breakoff at ca. 53 Ma. We propose that the slowdown of the Indian plate at ca. 51 Ma is largely the consequence of slab breakoff of the Neo-Tethyan oceanic lithosphere, instead of the onset of the India–Asia collision as traditionally interpreted, implying that the initial India–Asia collision commenced earlier, and likely ca. 5754 Ma.


Author index

Agnihotri, D., 110 Aitchison, J.C., 58 Alemu T., 10 Alexander E., 18 Amrouch, K., 5 Anand,S.V., 1, 3 Andreeva, E., 107 Arboit, F., 5 Archibald D., 6 Ariskin A.A., 8 Arita, K., 172 Ba, J., 176 Backe, G., 18 Bai, S. P. L., 182 Bergomi, M. A., 174 Berraa, F., 174 Bertram C., 18 Bilali H, E., 24 Blades M, L., 10 Brown M., 11 Cao, Y., 75 Cao, Y.T., 143 Cawood, P.A., 185 Chang K., 14 Chatterjee, S., 136 Chen, H., 80 Chen, L., 92 Chen, N. S., 176

Cheng, S., 41 Cheong, W., 70 Chetty T, R, K., 16, 52 Cho, M., 70 Chung, S.L., 185 Collins A, S., 5, 6, 10, 18, 31, 143 Danyushevsky L.V 8 Deng, J., 146, 159 DePaolo, D., 184

Dhang P, C., 18 Dong, G.C., 75 Dong, Y., 132 Donskaya T, V., 22, 33 Dumitru–Roban, R., 94 Egorova, V., 125 Ernst R, E., 25 Falster G., 18 Fang, X., 158 Fedorovsky V, S., 22 Fidaev, D., 65

Foden J., 6, 10 Gao, X.Y., 96 Gatinsky Y., 27 Geng, H., 67 Gladkochub D, P., 22, 33 Goldfarb, R. J., 37 Gore, R., 18 Groves, D. I., 39 Guo, A., 41 Guo, L., 43,159, 179 Guo, P., 46 Gupta, S., 48 Halverson G, P., 18 Hand, M., 59 He, C., 49 He, D., 51, 73, 78, 92 He, S.P., 143 Hegner, E., 67 Huang, T., 152, 179 Iinuma, M., 52 Izokh, A., 125

Izokh, A.E., 138 Izokh, N.G., 105 Jahn, B., 55 Jak, G., 31, 35 Jiang, C., 171 Jiang, T., 58 Johan, D. G., 35 Jourdan F., 18 Jowitt S, M., 25 Ke, S., 81 Kelsey, D. E., 59 Kim, S. W., 61, 68 King R., 5 Kislov, E.V., 8 Klemd, R., 65 Kobayashi, A., 63 Kolotilina, T.B., 138 Konnikov, E.G, 8 Konopelko, D., 65 Korsakov, A. V., 96 Kotov, A.B., 128 Kröner, A., 67 Kwon, S., 61, 68 Lebedev, V., 123 Lee, Y., 70 Lei, Q.P., 71 Li, C., 165

Li, D., 51, 73 Li, J., 78 Li, L., 75 Li, M., 143 Li, Q., 75 Li, R., 179 Li, R.S., 143 Li, S.R., 46, 75 Li, Y., 78, 80, 92, 183 Li, Z., 3, 80,163 Lian, Y., 51,73 Liu, D., 67, 81, 184 Liu, H., 182 Liu, L., 143 Liu, P., 82 Liu, Q., 71 Liu, S.A., 81, 185 Liu, Y., 84, 152, 179 Lu, F., 171 Ma, D., 51, 73 Mackintosh, J., 18 Malaspina, N., 174 Malaviarachchi, S., 130 Mamadjanov. Y., 65 Mataibayeva, I., 88 Mazukabzov A, M., 22, 33 Mccuaig, T. C., 146 Meert, J. G., 90 Mei, Q., 78, 92 Mekhonoshin, A.S., 138 Melinte-Dobrinescu,M.C.,94 Mikhael, B., 35 Mikhno, A.O., 96 Mikolaichuk, A., 99 Miroshnikova, A., 102 Mo, X., 81, 148, 184, 185 Morley C, K., 5 Murphy, J. B., 104 Nance, R. D., 104 NandaKumar, V., 67 Nikolaev G.S 8 Niu, Y., 81, 184, 185 Obut, O.T., 105 Okamoto, K., 55 Okrugin, V., 107 Orsoev, D.A., 138 Pandian, M.S., 3 Pandita, S.K., 110 Patranabis-Deb S., 18 Payne J., 6, 10, 18

http://petrology.oxfordjournals.org/search?author1=T.+Campbell+Mccuaig&sortspec=date&submit=Submit

187

Peng, P., 183 Polyakov,G.V., 138 Prokhorova, T., 27 Prokoph, A., 112 Rafailovich, M., 102 Razakamanana T., 6 Ren, H., 158 Roberts, N. M .W., 113 Rosenbaum, G., 122

Ryu, I.C., 61 Safonova, I., 99, 115, 123 Saha D., 18 Saitoh, Y., 117 Sakai, T., 172 Santosh, M., 37, 46, 49, 52, 61, 63, 67, 68, 75, 120, 130,132, 134, 141,169, 171, 176 Seltmann. R., 88, 102 Sergeev, S., 65 Shaanan, U., 122 Shaji, E., 67 Shang, C.K., 67 Sharkov, E., 123 Shatov. V., 88

Shelepaev, R., 125 Shen, J.F., 75 Shi, C., 143 Shunli D., 20 Sivasubramanium, R., 3 Sklayrov, E.V., 128 Sklyarova, O.A., 128 Skovitina, T.M., 128 Song, C., 158 Spencer, C. J., 113 Stijin, G., 31, 35 Sun, H., 80 Sun, M., 67, 176 Sun, W.Y., 75 Takamura, Y., 130 Tang, J., 51, 73

Tang, L., 132 Tang, Q., 165 Teng, X., 134 Tewari, R., 136 Titov, D., 102 Tolmacheva, E.V., 128 Tolstykh, N.D. , 138 Tong, Y., 55 Tsunogae, T., 52, 63, 117, 130, 141 Upreti, B. N., 172 Usuki, M., 55 Valui, G., 55 Vander Hilst, R.D., 182 Velikoslavinsky, S. D., 128 Vishnevsky, A., 125 Wan, X., 58 Wan, Y., 67 Wang, C., 143, 146 Wang, L., 148 Wang, Q., 81, 146, 185 Wang, Q.Y., 176 Wang, T., 55 Wang, X., 75, 183 Wang, Y., 149 Wang, Y.H., 143 Wang, Z., 43, 152, 159, 179 Wen, Z., 92 Wenjiao, X., 31, 35 Widom, E., 81 Wilde, S. A., 155 Woldetinsae G., 10 Wong, J., 67 Wormald, R., 122 Wu, F.Y., 185 Xie, H., 67 Xing, Y., 80 Xu, X., 10 Xu, H., 75 Xu, Q., 182 Xuheng F., 1

Yan, M., 158 Yang, L., 43, 152, 159, 179 Yang, Q., 75 Yang, Q.Y., 169 Yang, S., 80 Yang, W.Q., 143 Yang, X., 163 Yang, Y., 51, 73 Yao, A., 41 Yao, H., 182 Yi, K., 70 Yi, Z., 51, 73 Yin, Z., 171 Yizhou, H., 1 Yoshida, M., 172 Yu, H.Y., 143 Yu, M., 165 Yu, P.M., 138 Yu.A K., 8 Yuhuo Z., 1 Zanchetta, S., 174 Zanchi, A., 174 Zhang, B.L., 152 Zhang, D., 158 Zhang, G., 41 Zhang, H., 165 Zhang, H.F., 152 Zhang, J.Q., 75 Zhang, L., 78, 92 Zhang, L.J., 75 Zhang, M., 165 Zhang, R., 179 Zhao, J., 182 Zhao, R.X., 152 Zhao, X., 183 Zhao, Z., 81, 148, 184 Zhao, Z.D., 185 Zheng, X.L., 152 Zhiyong, Z., 31, 35 Zhong L., 20 Zhu, D.C., 81, 184, 185 Zhu, Q., 171 Zou, S., 80

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