paleoproterozoic arc magmatism in the north …paleoproterozoic arc magmatism in the north china...

Gondwana Research 28 (2015) 82–105

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Paleoproterozoic arc magmatism in the North China Craton: No Siderianglobal plate tectonic shutdown

Qiong-Yan Yang a, M. Santosh a,b,⁎a School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, Chinab Faculty of Science, Kochi University, Akebono-cho 2-51, Kochi 780-8520, Japan

⁎ Corresponding author at: School of Earth Sciences andGeosciences Beijing, 29 Xueyuan Road, Beijing 100083, Ch

E-mail address: [email protected] (M. Santosh)

http://dx.doi.org/10.1016/j.gr.2014.08.0051342-937X/© 2014 International Association for Gondwa

a b s t r a c t
a r t i c l e i n f o
Article history:Received 20 June 2014Received in revised form 3 August 2014Accepted 3 August 2014Available online 23 August 2014

Handling Editor: S. Kwon

Keywords:Zircon U–Pb geochronologyGeochemistryContinental arc magmatismCrustal growth and recyclingNorth China Craton

Arc magmatism in convergent plate margins has been amajor contributor to continental growth. Following arc–arc and arc–continent collisions in the Archean leading to the amalgamation of micro-blocks, the North ChinaCraton (NCC) witnessed major pulses of continental arc magmatism during the Paleoproterozoic. In this study,we present geochemistry, zircon U–Pb geochronology and Lu–Hf isotope data from a suite of magmatic rockssampled from the region of confluence of two major Paleoproterozoic suture zones in the NCC — the InnerMongolia Suture Zone (IMSZ) and the Trans-North China Orogen (TNCO). Our zircon U–Pb geochronologicaldata indicate new zircon growth duringmultiple tectonothermal events as displayed in the 207Pb/206Pbweightedmean ages of 2410 ± 41 Ma for metagranite, 2480 ± 12 Ma, 2125 ± 18 Ma, 1946 ± 8 Ma, 1900 ± 15 Ma and1879 ± 12 Ma from metagabbros, 2446 ± 11 Ma from charnockite, and 1904 ± 6 Ma and 1901 ± 9 Ma frommetatuffs. The 207Pb/206Pb upper intercept age of zircons in the khondalite shows 2102 ± 76 Ma which is iden-tical to the age obtained from themagmatic zircons in one of themetagabbros. The khondalites also carry a groupof concordant metamorphic zircons with 207Pb/206Pb mean age of 1881 ± 20 Ma. Metamorphic zircons in thegabbros and charnockites also yield similar ages of 1890 ± 14 Ma and 1852 ± 19 Ma respectively. The agedata suggest prolonged arc magmatism in a convergent margin setting during ca. 2.48 to 1.9 Ga, followed bymetamorphism at ca. 1.89–1.85 Ga associated with the final collision. Lu–Hf analyses reveal that the dominantpopulations of zircons from all the rock types are characterized by positive εHf values (−1.9 to 6.8; mean 1.8).The εHf and TDMC data suggest that the magmas were mostly derived from Neoarchean and Paleoproterozoic ju-venile components. The salient geochemical features of these rocks attest to magma generation from heteroge-neous sources involving subduction-derived arc components with minor input from continental crust. Theresults presented in this study, together with those from previous investigations in different domains of theIMSZ and TNCO suggest major Paleoproterozoic arc magmatic events in the NCC lasting for nearly600 million years associated with the final assembly of the crustal blocks into a coherent craton. Constructionof the final cratonic architecture of the NCC thus witnessed not only the arc–continent amalgamations at 2.7–2.5 Ga, but also major crust building events in the Paleoproterozoic through melts generated from juvenile andrecycled components in continental magmatic arc systems along an active convergent margin, followed by in-tense deformation andmetamorphismduring thefinal collision at 1.85–1.80Ga. The prominent Paleoproterozoicmagmatic records in the NCC do not support the proposal of global plate tectonic shutdown in the Siderian andconfirm vigorous convergent marginmagmatism and crust building processes throughout the Paleoproterozoic.

© 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

1. Introduction

The subduction of oceanic lithosphere in convergent marginsgives rise to arcmagmatism (Stern, 2002), with a pronounced composi-tional link between the trench input and arc output (Straub andZellmer, 2012). Arc magmatism in space and time under differentgeodynamic settings ranges from intra-oceanic arcs associated withocean–ocean convergence, plume–arc interaction, arc–backarc, and

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active continental margin setting associated with ocean–continent sub-duction (e.g., Manikyamba and Kerrich, 2012; Straub and Zellmer,2012; Santosh et al., 2013a). Condie and Kröner (2013) noted thatwith few exceptions, post-Archean accretionary orogens compriseb10% of accreted oceanic arcs, whereas continental arcs compose40–80% of these orogens. From Nd and Hf isotopic data, they showedthat accretionary orogens on the globe include 40–65% juvenile crustalcomponents, withmore than 50% of these produced in continental arcs.Due to higher degrees of partial melting in the mantle, oceanic arcs inthe Archean were thicker as compared to their Proterozoic equivalents.Condie and Kröner (2013) suggested that the vigorous onset of platetectonics in the late Archean with rapid production of continental

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83Q.-Y. Yang, M. Santosh / Gondwana Research 28 (2015) 82–105

crust witnessed a major transition in the primary site of production ofcontinental crust from accreted oceanic arcs and oceanic plateaus inthe Archean to dominantly continental arcs thereafter.

Convergent plate margins are potential regions of crustal growthwhere magmas derived by melting of mantle wedge fluxed with slab-dehydrated fluids and subducted slab result in vertical growth andthickening of arc crust, whereas the accretion of oceanic and trenchma-terials onto the active continental margins causes lateral growth(Santosh, 2013). Subduction-derived mafic magmas and crust-derivedfelsic magmas in arc settings thus contribute to vertical growth of thecrust (e.g., Foley et al., 2002; Rudnick and Gao, 2003). Tholeiitic tocalc-alkaline mafic, intermediate and felsic magmas are generated inactive margins through a combination of processes including influx ofslab-dehydrated fluids and melts into mantle wedge, wedge melting,assimilation of crustal materials by arc magma and magma mixing(Gao et al., 2012; Santosh et al., 2013a; Samuel et al., 2014;Manikyamba et al., in press). In a recentmodel, Castro et al. (2013) pro-posed relamination from below the lithosphere as an alternate mecha-nism for new crust generation in magmatic arcs of active continentalmargins and mature intraoceanic arcs, and explained the dominantlyandesitic composition of the continental crust.

The North China Craton (NCC) (Fig. 1) preserves important rock re-cords of early Precambrian crustal growth and microcontinent amal-gamation. The Neoarchean greenstone belts that surround the micro-blocks in the NCC are considered to represent the vestiges of olderarc–continent collision (Zhai and Santosh, 2011). Subsequently, theNCC witnessed a prolonged subduction–accretion history from earlyto the late Paleoproterozoic associated with the amalgamation ofmajor crustal blocks and the final cratonization (Zhai and Santosh,2011; Santosh et al., 2012, 2013b; Zhao and Zhai, 2013). Twomajor con-vergent margins, one running E–W between the Yinshan and OrdosBlocks and the other trending N–S between the Western and EasternBlocks, possibly in a double-sided subduction realm (Santosh, 2010)generated voluminous arc magmas of diverse composition during thePaleoproterozoic (e.g., Zhao et al., 2008; Dan et al., 2012; Liu et al.,2012; Santosh et al., 2012) which were subsequently incorporatedwithin the two major collisional sutures, termed as the InnerMongolia Suture Zone (IMSZ) and the Trans-North China Orogen

Fig. 1. Generalized tectonic framework of the North China Craton showing the major crustal blstudy area in Fig. 2 is shown by box.

(TNCO), respectively. Post-collisional magmatism related to slabbreak-off has also been recorded from a number of localities alongthese suture zones (e.g., Yang et al., 2014a).

In this study, we investigate the geochemistry and zircon U–Pb geo-chronology and Lu–Hf isotopes in a suite of plutonic, volcanic andmetasedimentary rocks from the zone linking the two majorPaleoproterozoic subduction systems in the NCC — the IMSZ and theTNCO. We report a diverse assemblage of granitoids, charnockites,gabbros, felsic volcanic tuffs and khondalites from this region whichshows a common link to active convergent margin tectonics andmagmatism within continental arc settings. Our results compare withthe isotopic data of Paleoproterozoic arc magmatic suites reportedfrom elsewhere in these zones suggesting an important phase of conti-nent building in the NCC during the Paleoproterozoic.

2. Geological setting

2.1. North China Craton

The North China Craton (NCC) (Fig. 1) is a collage of severalmicro-continents that preserve the history of Neoarchean crust for-mation, which were subsequently incorporated into two majorcrustal blocks by the late Neoarchean, the Eastern and WesternBlocks (e.g., Zhai and Santosh, 2011; Geng et al., 2012; Zhao andZhai, 2013). The final collision and cratonization of these crustalblocks occurred during the late Paleoproterozoic at around 1.85–1.80 Ga (e.g., Wilde et al., 2002; Kusky and Li, 2003; Zhao et al.,2005; Kusky et al., 2007; Santosh et al., 2007; Zhao et al., 2008;Santosh, 2010; Zhai and Santosh, 2011; Peng et al., 2011; Liu et al.,2012; Santosh et al., 2013b; Zhao and Zhai, 2013). The NCC is bor-dered on the south by the Qinling–Dabie Shan orogen, to the northby the Central Asian Orogenic Belt, and to the east by the Su-Lu belt(e.g., Zhai and Santosh, 2011; Zhao and Zhai, 2013).

The Western Block formed by amalgamation of the Ordos Block inthe south and the Yinshan Block in the north along the east–west-trending IMSZ (incorporating the Khondalite Belt) at 1.90–1.95 Ga.This was followed by the final collision between theWestern and East-ern Blocks along the TNCO at ca. 1.85–1.80 Ga (e.g., Zhao et al., 2005;

ocks and intervening suture zones (after Zhao et al., 2005; Santosh, 2010). The location of

84 Q.-Y. Yang, M. Santosh / Gondwana Research 28 (2015) 82–105

Santosh et al., 2007; Zhai and Santosh, 2011; Santosh et al., 2013b; Zhaoand Zhai, 2013) in a double-sided subduction realm, broadly coevalwith the global assembly of the Columbia supercontinent into whichthe NCC was incorporated at this time (Santosh, 2010). The YinshanBlock is composed of low-grade granite–greenstone and high-gradeTTG (tonalite–trondhjemite–granodiorite) gneiss and granulite ter-rains, with greenschist to granulite facies metamorphism at ca. 2.5 Gaand preserves broad structural style and metamorphic history similarto that of the Eastern Block (Liu et al., 1993). The Ordos Block is largelycovered by Mesozoic to Cenozoic strata of the Ordos Basin (Zhao et al.,2005). The Eastern Block preserves some of the oldest rock records inthe NCC (Zhai and Santosh, 2011) and is considered to have witnessedPaleoproterozoic rifting along its eastern margin during 2.2–1.9 Ga,and subsequent closure along the Jiao-Liao-Ji Belt (Zhao and Zhai,2013, and references therein).

2.2. Inner Mongolia Suture Zone

The IMSZ, within which the Khondalite Belt is distributed, is consid-ered as the suture zone along which the Yinshan Block in the north andthe Ordos Block in the south amalgamated to form the coherent West-ern Block of the NCC during the late Paleoproterozoic (e.g., Zhao et al.,2005, 2006; Santosh et al., 2007; Zhai and Santosh, 2011; Santoshet al., 2012, 2013b; Zhao and Zhai, 2013). The northern margin of theIMSZ is marked by the E–W trending ductile shear zones between thePaleoproterozoic lithologies within the IMSZ and the Neoarchean TTGgneisses and granulites in the Yinshan Block. The northeast-trendingductile shear zone between the Paleoproterozoic khondalites withinthe IMSZ and the Paleoproterozoic high-pressure-granulite-bearingTTG gneisseswithin the TNCO represents its easternmargin. The south-ern margin of the IMSZ is covered by Phanerozoic sedimentary strata.The Helanshan–Qianlishan, Daqingshan, and Jining–Liangcheng–Fengzhen are the major belts occurring within the IMSZ. The rocktypes in these belts have been broadly grouped into accretionary se-quence and continental arc components, both of which were subjectedto granulite-facies metamorphism during the Paleoproterozoic colli-sional event (Santosh, 2010). The varied lithological associations inthe IMSZ including amphibolites, metachert, metagabbro, and marble,with a vast sequence of quartzite, and metapelitic units have been cor-related to a long-lived subduction–accretion of both oceanic and conti-nental components. The TTG gneisses, charnockites and calc-alkalinegranites are thought to represent a continental arc. Thus, the KhondaliteBelt has been redefined as amajor Paleoproterozoic collisional suture, asthe Inner Mongolia Suture Zone (Santosh, 2010).

The khondalites in the IMSZ have attracted considerable attentionin recent studies following the discovery of ca. 1.92 Ga ultrahigh-temperature granulites representing extreme metamorphism undertemperatures exceeding 1000 °C and pressures around 10 kbar(Santosh et al., 2006, 2007, 2008, 2009; Liu et al., 2011; Tsunogaeet al., 2011; Guo et al., 2012; Zhang et al., 2012; Jiao et al., 2013;Santosh et al., 2013b; Yang et al., 2014b). Sapphirine-bearing granulitesin Tuguiwula and Daqingshan, and spinel- and cordierite-bearingkhondalites elsewhere in several localitieswithin the IMSZ have provid-ed insights into the metamorphic and tectonic history associated withthe subduction–collision tectonics along the IMSZ (e.g., Santosh et al.,2013b).

2.3. Trans-North China Orogen

The 100–300kmwide and ca. 1200km long and nearlyN–S trendingTNCO represents the collisional suture between the Eastern andWestern Blocks of the NCC (Zhao and Zhai, 2013). The TNCO has beensubdivided into two major domains: (1) high-grade areas (includingthe Taihua, Fuping, Hengshan, Huai'an, and Xuanhua Complexes) and(2) low-grade granite–greenstone terrains (including the Dengfeng,Zhongtiao, Zanhuang, Lüliang and Wutai Complexes) (Zhao et al.,

2001, 2008). The occurrence of high-pressure granulites andretrograded eclogites in some locations within the TNCO has beentaken to indicate that this zone represents a major continent–continentcollision zone (Zhao et al., 2001;Wilde et al., 2002; Li and Kusky, 2007;Trap et al., 2007; Zhao et al., 2008, among others). Kröner et al. (2005a,b) proposed that the TNCO represents an Andean-type continentalmar-gin or a Japan-type island arc. The earliest arc magmatic event in theTNCO is recorded by a suite of granitoids emplaced at 2.56–2.52 Ga(Wilde et al., 2005), with the final collision between the Eastern andWestern Blocks recorded from the timing of metamorphism at1880–1820 Ma, a time span of more than 650 Ma (Zhao et al., 2008;Zhao and Zhai, 2013). Santosh et al. (2013b) proposed a long lived sub-duction–accretion history prior to the final collisional amalgamation ofthe major crustal blocks in the NCC during the late Paleoproterozoic.The Paleoproterozoic metamorphic complexes in the TNCO includethe Lüliang, Zhongtiao, Zanhuang, Taihua and Northern Hebei. Amongthese, the Lüliang complex has been well studied and the systematicgeochronological data presented by Zhao et al. (2008) from the variousrock suites in this complex provide insights into the pre-, syn- and post-collisional history. The pre-tectonic rocks in the complex aremostly TTGgneisses with calc-alkaline chemistry and magmatic arc affinity whichwere emplaced at ca. 2.5 Ga, representing the earliest arc-related mag-matic event. This was followed by arc-related magmatic pulses at 2.4and 2.2 Ga. Metamorphism associated with collision occurred at ca.1.87 Ga. Subsequently, a series of post collisional granitoids includingporphyritic granite, charnockite, and massive granite were emplacedduring 1.83 to 1.79 Ga.

Liu et al. (2012) reported geochemical and zircon U–Pb data frommetavolcanic units in the Yejishan and Lüliang groups of the LüliangComplex in TNCO. Their geochemical modeling shows that the parentalmagma of these metavolcanics was derived from the partial melting ofsubduction-enriched spinel lherzolites and spinel–garnet lherzolites,with subsequent fractional crystallization and assimilation of continentalmaterial. Their data are consistent with a magmatic arc system in an ac-tive continental margin, generating widespread arc-related magmatismat 2.2 Ga, followed by metamorphism during 1.90–1.83 Ga associatedwith the collisional event and post-collisional extension at 1.80 Ga.

Late Paleoproterozoic post-collisional magmatic suites also occur inthe central and southern segments of the TNCO represented bycharnockites, granites, mafic dykes and volcanic suites (e.g., Genget al., 2004; Peng et al., 2005, 2008; Hou et al., 2008; Liu et al., 2009;Zhao et al., 2009; Wang et al., 2010). These rocks range in age from ca.1.68 Ga to 1.78 Ga and are considered to extend for more than 500 kmacross the border between the TNCO and the Eastern Block along thenorthern margin of the NCC. In a recent study, Yang et al. (2014a) re-ported petrological, geochemical and zircon U–Pb geochronologicaland Lu–Hf data from a pyroxenite (websterite)–gabbro–diorite suiteat Xinghe in Inner Mongolia along the northern segment of the TNCO.The LA-ICPMS U–Pb data show emplacement ages of 1786.1 ± 4.8 Ma,1783 ± 15 Ma, 1767 ± 13 Ma 1754 ± 16 Ma and 1754 ± 16 Ma, withdominantly positive εHf(t) values (up to 5.8), suggesting magma deri-vation from juvenile sources. Yang et al. (2014a) correlated themagma genesis with post-collisional extension during slab break-offfollowing thewestward subduction of the Eastern Block and its collisionwith the Western Block. Asthenospheric upwelling and heat input areconsidered to have triggered the magma generation from a heteroge-neous, subduction-modified sub-lithospheric mantle source.

2.4. Study area

Our present study areas in the Xinghe and Jining regions of InnerMongolia are located at the junction between the E–W trending IMSZand the approximately N–S trending TNCO (Figs. 1, 2), and includethree distinct terranes, the Huai'an, Fengzhen, and Yinshan, juxtaposedfrom southeast to northwest. TheHuai'an terrane is largely composed ofca. 2.5 Ga tonalite–trondhjemite–granodiorite (TTG) gneisses and 2.0 to

Fig. 2. Geological map of part of the North China Craton showing the study area and locations of samples analyzed in this study.


1.9 Ga potassic granitoids into which are emplaced Paleoproterozoicmafic dykes that have undergone ca. 1.85 Ga high-pressure granulite fa-cies metamorphism (e.g., Zhai et al., 1992; Liu et al., 2009; Peng et al.,2010). The Yinshan terrane comprises the ca. 2.5 Ga late Archean TTGgneisses and granulites, along with granite–greenstone belt (e.g., Zhaoet al., 2005), and covered by Paleoproterozoic sediments (Wan et al.,2009). The Fengzhen terrane incorporates the ‘Khondalite Belt’ com-prising a vast Paleoproterozoic accretionary sequence of psammopelitic,pelitic, volcanic and carbonate sediments metamorphosed to high andultra-high temperature conditions, together with imbricated oceanicfragments (amphibolites, metagabbros, Banded Iron Formations), andarc-related continental fragments (charnockites, granitoids) developedduring a prolonged subduction–accretion history prior to final collisionin the late Paleoproterozoic (Santosh et al., 2012, 2013b). The majorrock types in this area include charnockites, TTG gneisses, khondalites(granulite facies metapelites), and minor Banded Iron Formations. TheTTG gneisses locally incorporate lenses and blocks of garnet-bearingmafic granulites. The khondaliteswere thought to represent continentalshelf sequences, incorporating abundant graphite mineralization such

Table 1Details of samples analyzed for whole rock geochemical analysis and zircon U–Pb and Hf isoto

No. Sample no. Rock type Locality

1 OY-XH-1A Metagranite Xinghe area (GPS coordinates N40° 43′ 26.23″2 OY-XH-12 Metagranite Longshengzhuang village (GPS coordinates N43 OY-XH-7A Charnockite Zhujiaying village (GPS coordinates N40° 36′4 IM13-18 Metagabbro Tuguiwula area (GPS coordinates N40° 46′ 425 IM13-19 Metagabbro Tuguiwula area (GPS coordinates N40° 45′ 466 IM13-20 Metagabbro Tuguiwula area (GPS coordinates N40° 45′ 467 OY-XH-1B Metagabbro Xinghe area (GPS coordinates N40° 43′ 26.23″8 OY-XH-9A Felsic tuffs Longshengzhuang village (GPS coordinates N49 OY-XH-11 Felsic tuffs Longshengzhuang village (GPS coordinates N410 OY-XH-3A Khondalite Xinghuagou village (GPS coordinates N40° 52

Mineral abbreviations: Opx — orthopyroxene; Cpx — clinopyroxene; Bt— biotite; Hbl — hornbzircon; Grt — garnet; Sil — sillimanite.

as that in the Huangtuyao mine, although some of the recent studiessuggest that the protoliths of these rocks also involved active marginvolcanic input in an arc-related setting (Dan et al., 2012).

Samples for the present study were collected from several locationsin the Jining area belonging to the Jining–Liangcheng–Fengzhen com-plex and from the Xinghe are belonging to the Huai'an terrane of theNorthernHebei complex (Fig. 2). The sample locations, GPS coordinates,rock types and summary of mineral assemblages are given in Table 1,and representative field photographs are shown in Fig. 3.

3. Rock types and petrography

The rock types analyzed in this study for geochemistry and zirconU–Pb geochronology and Lu–Hf isotopes includemetagranite, charnockite,metagabbro, meta-tuff and khondalite. A brief description of the rocktypes and their petrography (as studied from polished thin sections atthe Peking University, China) is given below. Representative photomi-crographs showing the mineral assemblages and textures are given inFigs. 4–5.

pes.

Mineralogy

; E114° 09′ 05.31″; height 1122 m) Kfs+Pl+Qtz+Bt0° 43′ 08.26″; E113° 25′ 34.65″; height 1363 m) Kfs+Pl+Qtz+Bt+Grt20.88″; E113° 58′ 50.76″; height 1298 m) Pl+Kfs+Qtz+Cpx+Opx+Hbl.15″; E113° 15′ 08.43″; height 1305 m) Pl+Cpx+Opx+Hbl+Mt.35″; E113° 15′ 11.92″; height 1332 m) Pl+Cpx+Opx+Mt.35″; E113° 15′ 11.92″; height 1332 m) Pl+Cpx+Opx+Bt+Mt+Ap; E114° 09′ 05.31″; height 1122 m) Pl+Cpx+Opx+Mt+Bt0° 42′ 01.98″; E113° 26′ 13.68″; height 1373 m) Kfs+Qtz+Pl+Grt+Bt0° 43′ 06.92″; E113° 25′ 37.40″; height 1371 m) Kfs+Qtz+Pl+Grt+Bt′ 47.98″; E113° 59′ 05.54″; height 1240 m) Kfs+Qtz+Pl+Grt+

Sil+Bt+Zr+Ap

lende; Kfs — K-feldspar; Pl — Plioclase; Qtz — quartz; Mt—magnetite; Ap— apatite; Zr—

Fig. 3. Representative field photographs. (a) Metagranite exposurewith enclaves of metagabbro (location OY-XH-1A and B in Table 1). (b) Porphyriticmetagranite (OY-XH-12). (c) Felsictuff layer (left) in association with garnet-bearing metapelitic rock (right) (OY-XH-9A). (d) Thin intercalation of felsic tuff in metapelite (OY-XH-11). (e) Greasy greencharnockite (OY-XH-7A). (f) Coarse porphyroblastic garnet and sillimanite bearing khondalite (OY-XH-3A).

Fig. 4. Representative photomicrographs of thin sections of the analyzed rock samples. (a) and (b): Charnockite. (c) and (d) Metagabbro. Mineral abbreviations: Opx —

orthopyroxene; Cpx — clinopyroxene; Hbl — hornblende; Pl — plagioclase; Kfs — K-feldspar.


Fig. 5. Representative photomicrographs of thin sections of the analyzed rock samples. (a) and (b): Metagranite. (c) Khondalite. (d) Felsic tuff. Mineral abbreviations: Grt— garnet; Sil—sillimanite; Bt— biotite; Pl— plagioclase; Kfs — K-feldspar; Qtz — quartz.


3.1. Metagranite

The metagranites in the study area occur either as large plutons ex-posed in massive hillocks, or as sheet-like intrusions ranging in thick-ness from several tens to few hundreds of meters emplaced withinTTG gneisses. At some places, the metagranites carry enclaves ofmetagabbros or meta-dioritic gabbros ranging up to a few meters insize such as in the Xinghe area (Fig. 3a). The metagranite in this studyis medium grained and shows prominent foliation defined by the align-ment of biotite flakes. Compositional banding is also displayed at someplaces, suggesting partial melting. In sample OY-XH-1A from Xinghe,the dominant minerals are pink K-feldspar, quartz, plagioclase and bio-tite. In the second location near Longshengzhuang (sample OY-XH-12),the metagranite shows prominent porphyritic texture (Fig. 3b) withcoarse grained pink K-feldspar (up to 5 cm in length) set in a mediumgrained matrix comprising plagioclase, quartz and biotite. The rockhas been deformedwith the feldspar crystals showing a preferred orien-tation along the foliation. The quartz is grayish and shows stretchingand elongation. Clots of porphyroblastic garnet are distributed alongthe foliation planes. In thin section perthitic K-feldspar (40%), quartz(40%), plagioclase (10%), garnet (5%) and biotite (2%) are the dominantminerals.

3.2. Charnockite

Charnockite is oneof the dominant rock types in theXinghe area andconstitute massive exposures extending from a few tens of meters toseveral kilometers (Fig. 3e). Locally veins and patches of incipientcharnockite also occur in some localities, developed through high tem-perature metamorphism during carbonic fluid influx from massivecharnockite into the adjacent TTG gneisses as reported in a recentstudy (Yang et al., 2014c). The charnockite analyzed in this study (OY-XH-7A) was collected from the Zhujiaying village, where the rock isemplaced within TTG gneisses. The charnockite is garnet-absent andcarries bands and enclaves of mafic granulites ranging in size from afew decimeters up to 10 m. The dominant mineral assemblage of the

charnockite is plagioclase (50%), K-feldspar (20%), quartz (15%)orthopyroxene (5%), hornblende (7%) and minor clinopyroxene (3%).Biotite is nearly absent. The pyroxene and plagioclase grains showsubhedral morphology and typical magmatic fabric.

3.3. Metagabbro

Metagabbros occur as massive exposures or as enclaves within thegranitoids (Fig. 3a), and are dark grayish andmedium grainedwith pla-gioclase, clinopyroxene, orthopyroxene and biotite. The metagabbroscollected from the Xinghe (samples OY-XH-1B) and Jining (IM13-18,IM13-19, IM13-20) areas for this study are melanocratic and mediumgrained. In thin section, the rocks are composed of plagioclase (40–45%), clinopyroxene (30–40%), orthopyroxene (10–15 vol.%), andminor hornblende, biotite and apatite (together 2–5%). Themetagabbrosfrom the Jining area show higher modal content of hornblende (up to10%, sample IM13-18) and biotite (up to 8%, sample IM13-19) togetherwithminor recrystallized quartz. Opaqueminerals are ilmenite andmag-netite (3–8%).

3.4. Felsic tuff

Metamorphosed felsic volcanic tuffs occur as dismembered se-quences intercalated with garnet- and biotite-bearing leptynitic rocksas in Longshengzhuang village (sample OY-XH-9A, Fig. 3c), or as thickmeter-sized layers in surrounding regions (sample OY-XH-11, Fig. 3d).These rocks are light gray colored, fine grained and show fine lamina-tion with sporadic subhedral and undeformed garnet grains. Despitemetamorphism and deformation, the rocks preserve relict primary tex-tures such as depositional lamina and clastic nature. The absence of anymetamorphic aluminosilicate minerals (such as sillimanite in the asso-ciated khondalite) other than the rare millimeter-sized porphyroblasticgarnets precludes a pelitic sedimentary source and suggests a volcanicorigin, similar to those reported from the Neoarchean convergent mar-gin sequences of Attappadi in southern India (Praveen et al., 2013). Thevolcanic origin is also confirmed from their rhyolite to rhyodacite com-position (see section on geochemistry). The thin laminations (b1 to


5 mm) in the rock defined by alternate mafic-rich and felsic-rich layerssuggest fluctuations in the debris input (Stix and Gorton, 1991). Theselaminations suggest deposition in moderate to deep-water conditions.In thin section, the rock shows sub-angular to sub-rounded grains ofquartz (35–45%), occurring in a groundmass of K-feldspar (50–55%),plagioclase (8–15%), biotite andminor garnet (together 2–3%). The feld-spars show variable degrees of alteration. The quartz grains are moder-ately to well-sorted and fine grained (b0.2 mm).

3.5. Khondalite

The khondalite sample OY-XH-3A is from a stream section in theXinghuagou village of the Xinghe area and the region forms part ofthe Jining–Liangcheng–Fengzhen sector of the Khondalite Belt in theNCC. The rock is medium grained and foliated with garnet–sillimanite-rich bands alternating with quartzofeldspathic layers (Fig. 3f). Thekhondalite in the present study does not contain graphite, as againstthe various types of graphite-bearing metapelites reported fromadjacent regions (e.g., Yang et al., 2014d). The rock also does not showtypical UHT minerals like sapphirine in association with quartz,orthopyroxene + sillimanite and low-Zn spinel + quartz reportedfrom adjacent regions (e.g., Santosh et al., 2012; Yang et al., 2014b), sug-gesting a relatively low-Mg–K bulk composition. The major minerals inthis rock are feldspar (50% including K-feldspar (40%) and plagioclase(10%)), quartz (30%), garnet (10%) and sillimanite (8%), with minor bi-otite, zircon and apatite (together 2%). Although previous studies con-sidered the protoliths of the khondalites as passive margin sediments(e.g., Condie et al., 1992), recent works suggest that these rocks mighthave formed within an active margin in an arc-related setting (Danet al., 2012), which is consistent with our finding of felsic tuffs interca-lated with this rock suite in several localities as described below.

4. Analytical techniques

4.1. Zircon separation and CL imaging

Zircons grains were separated using standard procedures for U–Pbdating and Hf analyses at the Yu'neng Geological and Mineral Separa-tion Survey Centre, Langfang City, Hebei Province, China. The CL imag-ing was carried out at the Beijing Geoanalysis Centre. Individual grainswere mounted along with the standard TEMORA 1, with a 206Pb/238Uage of 417 Ma (Black et al., 2003), onto double-sided adhesive tapeand enclosed in epoxy resin discs. The discs were polished to exposethe central part of the grains and gold coated for cathodoluminescence(CL) imaging and U–Pb isotope analysis. Zircon morphology and inter-nal structure were examined using a JSM-6510 Scanning Electron Mi-croscope (SEM) equipped with a backscatter probe and a Chroma CLprobe. The zircon grains were also examined under transmitted andreflected light using a petrological microscope.

4.2. Zircon U–Pb and Hf isotopic analysis

Zircon U–Pb analysis was performed on laser ablation inductivelycoupled plasma spectrometry (LA-ICP-MS) housed at the Peking Uni-versity (Beijing) (samples OY-XH-1A, OY-XH-1B, OY-XH-3A, OY-XH-7A, OY-XH-9A and OY-XH-11), and the Tianjin Institute of Geologyand Mineral Resources (Tianjin) (samples IM13-19 and IM13-20). TheIM13-18 sample was analyzed by using SHRIMP II at the BeijingSHRIMP Centre. All the in situ zircon Hf isotopic analyses were per-formed at the Tianjin Institute of Geology and Mineral Resources. Theanalyses were conducted on the same spots or in adjacent domainswhere U–Pb dating was done.

Zircon U–Pb analysis at Peking University followed the analyticalprocedures reported in Yuan et al. (2004). In the LA-ICP-MS method,the laser spot diameter and frequency were 30 μm and 10 Hz, respec-tively. Zircon 91500 was employed as a standard and the standard

silicate glass NIST was used to optimize the instrument. Raw datawere processed using the GLITTER program to calculate isotopic ratiosand ages of 207Pb/206Pb, 206Pb/238U, and 207Pb/235U, respectively. Datawere corrected for common lead, according to the method ofAnderson (2002), and calculated the ages by ISOPLOT 4.15 software(Yuan et al., 2004).

At the Tianjin Institute of Geology and Mineral Resources, zircon U–Pb dating and in-situ Hf isotopic analyses were conducted using a Nep-tune MC-ICP-MS equipped with a 193 nm Geolas Q Plus ArF exciplexlaser ablation, with spot sizes of 35 μm and 50 μm, respectively. ZirconGJ-1was used as an external standard for U–Pb dating and in-situ zirconHf isotopic analyses. Common-Pb corrections were made using themethod of Anderson (2002). Data were processed using the GLITTERand ISOPLOT (Ludwig, 2003) programs. Errors on individual analysesby LA-ICP-MS are quoted at the 95% (1σ) confidence level. Details ofthe technique are described by Li et al. (2009) and Geng et al. (2011).

The analytical procedures using SHRIMP II followed those ofWilliams (1998). Data were processed and assessed using the softwareprograms Squid (Ludwig, 2001) and ISOPLOT (Ludwig, 2003). CommonPb correction was made using the measured 204Pb and applying thevalues of Stacey and Kramers (1975). Uncertainties for each analysisare at 1σ, whereas the weighted mean age is quoted at 2σ.

4.3. Whole rock major and trace element analyses

Major elements were analyzed on glass discs fused with Li-borateflux by X-ray fluorescence spectrometry (XRF) at the China Universityof Geosciences Beijing, following themethod of Harvey (1989). Trace el-ements (including REE) were analyzed by a Finnigan MAT Element 2,high resolution ICP-MS at the State Key Laboratory of Geological Pro-cesses and Mineral Resources (GPMR), following procedures describedby Qi et al. (2000). The Chinese national standard GSR-1 (Xie et al.,1989) was used as standard.

Major and trace elements of a few samples (IM13-18, 19 and 20)were determined by XRF (Phillips MAGIX PRO Model 2440) at the Na-tional Geophysical Research Institute (NGRI), India, on pressed pelletsprepared from powdered whole-rock samples. Volatiles were deter-mined by loss on ignition. The analytical technique is described in detailin Manikyamba et al. (2012). Trace and REEs were performed using HRICP-MS (Nu Attom) at NGRI. Precision and reproducibility obtained forinternational reference materials JG-2 and JGB-1 are 2–5% (1σ) formost elements.

5. Results

5.1. Whole-rock geochemistry

Whole rock geochemical data, includingmajor,minor, trace and rareearth elements, on the metagranites, metagabbros, charnockites, felsicvolcanic tuff and khondalites are given in Table 2. The salient geochem-ical features of the various rock types are summarized below.

5.1.1. Major elementsThe metagabbros show a restricted range in SiO2 varying between

48.75 and 49.48 wt.%, whereas one sample shows a dioritic compositionwith 54.23 wt.% SiO2. These rocks have moderate TiO2 contents rangingfrom 1.4–2.2 wt.%, moderate to high Al2O3 (12.5–16.2 wt.%), Fe2O3

(9.6–18.4 wt.%), MgO (5.5–9.9 wt.%) and CaO (6.3–9.6 wt.%) contents.Total alkali contents of these metagabbros are high in the range of3.42–6.5 wt.%. Mg# ranging from 38.1–66.4 indicates a progressive dif-ferentiation trend in the metagabbros. The major element chemistry ofthe khondalite is marked by 71. 23 wt.% SiO2, 0.71 wt.% TiO2, 15.1 wt.%Al2O3, 4.04 wt.% Fe2O3, 1.52 wt.% MgO and 1.4 wt.% CaO, whereas thecharnockite shows a relatively lower SiO2 content (56.31 wt.%), compa-rable TiO2 (0.76 wt.%), higher Al2O3 (17.25 wt.%), Fe2O3 (7.42 wt.%),MgO (4.57 wt.%) and CaO (7.12 wt.%). The charnockite shows relatively

Table 2Whole rock geochemical data from Xinghe and Jining, North China Craton.

Rock type Metagranites Charnockite Metagabbros Tuffs Khondalite

OY-XH-1A OY-XH-12 OY-XH-7a IM13-18 IM13-19 IM13-20 OY-XH-1B OY-XH-9A OY-XH-11 OY-XH-3A

SiO2 71.55 72.1 56.31 54.23 49.48 49.39 48.75 76.51 78.09 71.23TiO2 0.29 0.31 0.76 2.21 2.06 1.36 1.97 0.05 0.06 0.71Al2O3 14.86 13.89 17.25 13.99 15.36 16.1 12.53 13.54 12.01 15.1Fe2O3

(T) 1.65 2.52 7.42 9.64 10.27 10.06 18.38 0.14 0.72 4.04MnO 0.01 0.03 0.11 0.11 0.14 0.13 0.27 0 0.02 0.05MgO 0.47 0.91 4.57 5.73 9.92 8.82 5.51 0.07 0.3 1.52CaO 1.45 1.59 7.12 6.27 8.38 9.2 9.59 1.82 1.07 1.4Na2O 3.66 2.31 5.13 3.04 3.13 2.1 2.65 3.65 3.79 1.81K2O 4.77 4.87 1.27 3.62 1.18 2.61 0.75 2.27 2.04 2.74P2O5 0.17 0.24 0.25 0.82 0.72 0.63 0.33 0.17 0.05 0.07LOI 0.61 0.39 0.23 0.94 0.77 0.56 −0.18 0.84 0.93 0.82Total 99.5 99.14 100.42 99.66 100.64 100.4 100.55 99.06 99.09 99.49Mg# 37.0 42.5 55.8 54.9 66.4 64.2 38.1 50.2 46.1 43.6Cr 3.7 24.5 102.7 4.6 5.3 5.6 70.4 1.2 3.3 77.6Co 3.1 3.9 25.5 23.9 30.9 41.5 60.9 0.5 1.1 8.2Ni 6.4 3.9 50.9 15.6 18 22.2 63.9 1.5 1.8 17.7Rb 95 244.7 7.1 65.5 10.9 77.2 11.1 46.5 59 89.3Sr 421.1 200.6 661.4 912.6 1447.6 966.5 126.2 126.1 302.9 168.8Li 12.5 32 11.1 8.8 25.4 36 14Cs 0.1 0.9 0 0 0 0.2 0 0.4 0.6 0.5Be 0.6 4.1 1.3 1.1 1 3.4 0.4Ba 1261 514 558 2224 613 2227 277 175 565 571Sc 1.8 7.3 19.3 12 16.3 21.8 47.6 0.6 1.8 9.2V 22.2 26.4 144.6 7.3 9.8 14.1 406.5 2.5 4.5 74.6Ta 0 0.6 0.3 2.9 2 1.1 0.6 0 0.1 0.2Nb 2.5 8.8 7.8 46.5 23.8 15.2 10.2 0.2 0.4 8Zr 157 145 160 517 71 293 162 129 51 304Hf 3.9 4 3.7 8.7 1.7 6.1 4.3 3.4 1.3 8Th 1.1 18.8 0.3 0.7 1.3 0.6 0.3 0.4 0.4 1.4U 0.2 2.3 0.1 0.4 0.3 0.4 0.2 0.2 0.3 0.5Y 2.4 22.4 15.4 40.8 19.8 30.6 51.4 3.9 4.5 20.3Cu 3.2 1.5 33.2 1.5 1.7 1.8 81.8 1.9 1.3 2Zn 29.1 31.8 89.5 83.2 40.9 57.3 144 7.4 13.3 68.5Pb 10.6 27.4 3.8 9.2 9.4 9.4 1.3 14.2 10 13.7Ga 18.8 18.4 21.6 26.9 28 26.7 19.7 14.8 13.6 22.6La 20.40 46.20 25.30 70.60 57.40 49.80 15.10 68.40 22.20 36.70Ce 32.90 99.40 58.80 151.80 128.10 111.10 38.50 112.00 34.10 71.20Pr 3.20 11.60 7.60 23.60 20.10 17.80 5.40 10.50 3.20 7.80Nd 10.70 42.90 31.30 89.30 76.10 70.60 25.40 32.30 9.60 27.50Sm 1.50 7.90 5.70 16.60 14.10 14.00 6.60 3.70 1.20 4.50Eu 0.90 1.00 1.50 3.30 2.20 3.60 2.00 1.10 0.40 1.20Gd 1.00 5.60 4.30 10.10 7.60 8.40 7.70 2.20 0.90 3.90Tb 0.10 0.80 0.60 1.50 1.00 1.20 1.30 0.20 0.10 0.60Dy 0.50 4.20 3.00 6.50 3.90 5.40 8.70 0.80 0.80 3.40Ho 0.10 0.80 0.60 1.00 0.50 0.80 1.80 0.10 0.20 0.70Er 0.20 0.10 1.50 2.70 1.40 2.20 5.20 0.30 0.40 2.10Tm 0.00 0.30 0.20 0.40 0.20 0.30 0.80 0.00 0.10 0.30Yb 0.10 2.00 1.30 2.30 1.10 2.10 5.00 0.30 0.50 2.20Lu 0.00 0.30 0.20 0.30 0.20 0.30 0.80 0.10 0.10 0.30Fe/Fe + Mg 0.8 0.7 0.6 0.6 0.5 0.5 0.8 0.7 0.7 0.7Na + K − Ca 7 5.6 −0.7 0.4 −4.1 −4.5 −6.2 4.1 4.8 3.2A/CNK 1.1 1.2 0.8 0.7 0.7 0.7 0.6 1.2 1.2 1.8A/NK 1.3 1.5 1.8 1.6 2.4 2.6 2.4 1.6 1.4 2.5Na + K 8.4 7.2 6.4 6.7 4.3 4.7 3.4 5.9 5.8 4.6Sr/Y 173.5 8.9 42.9 22.4 73 31.5 2.5 32.4 66.8 8.3Nb/Zr 0 0.1 0 0.1 0.3 0.1 0.1 0 0 0K/Rb 416.6 164.9 1487.5 458.4 900.2 280.2 555.5 404.7 286.5 254.4Zr/TiO2 546.4 476 210.6 233.8 34.3 215.8 82.2 2571.2 810.2 427.5Y + Nb 5 31.3 23.2 87.3 43.7 45.8 61.6 4.1 4.9 28.3La/Yb 153.3 23.4 20.1 30.4 53.1 23.3 3 201.1 46.8 16.4Th/Yb 8.6 9.5 0.2 0.3 1.2 0.3 1.1 0.9 0.6Q 27.5 34.1 0 0 0 0 0 43.3 45.9 43An 7.3 8 20.2 13.9 24.2 26.7 19.9 9.2 5.4 7Ab 31.3 19.8 43.3 25.8 26.3 10.9 22.2 31.4 32.7 15.5Or 28.5 29.1 7.5 21.4 6.9 15.4 4.4 13.7 12.3 16.4K 39,552 40,349 10,539 30,013 9783 21,639 6187 18,820 16,891 22,719


higher total alkali content (6.4 wt.%) and Mg# (56) than those of thekhondalite (4.55 wt.%; 44). The tuffs are characterized by high SiO2

contents in the range of 76.5–78.1 wt.%, extremely low TiO2 (0.05–0.06 wt.%), MgO (0.07–0.03 wt.%), low CaO (1.1–1.8 wt.%) and moder-ate Al2O3 (12–13.5 wt.%). These samples exhibit high total alkali

contents ranging from 5.83–5.92 wt.%. Mg# varying between 46 and50 suggests an evolved character. The metagranites characteristicallyshow high SiO2 (71.55–72.10 wt.%), moderate Al2O3 (13.9–14.9 wt.%),low Fe2O3 (1.65–2.52 wt.%), CaO (1.45–1.6 wt.%), extremely low TiO2

(0.29–0.31 wt.%) and MgO (0.01–0.03 wt.%) contents. Total alkali


contents are high in the range of 7.18–8.43 wt.%. These metagranitesdisplay an evolved character with Mg# varying between 37 and 43. Inthe total alkali vs. silica diagram (Le Bas et al., 1986; Fig. 6a) themetagabbros occupy the field of gabbro and monzodiorite showing asubalkaline to alkaline composition, and the charnockite falls in thefield of monzodiorite with a sub-alkaline affinity and the metagranitescorrespond to the field of sub-alkaline granite (Fig. 6a). The tuffs andkhondalite distinctively show rhyolite–dacite and rhyodacite–dacitecompositions respectively in Zr/TiO2 vs. SiO2 plot (Fig. 6b), similar tomagmatic rocks of active continental margin settings. In the An–Ab–Or diagram (Maniar and Piccoli, 1989), the charnockite shows tonaliticcomposition, the tuffs fall in the trondhjemite field, and themetagranites and khondalite fall in the granite field (Fig. 6c). In termsof A/NK vs. A/CNK relationships, the charnockite shows metaluminousaffinity, whereas the granites, tuffs and khondalite have peraluminouscomposition (Fig. 6d). Immobile trace element relationships suggest atholeiitic to transitional trend for the metagabbros and calc-alkaline af-finity for tuffs, khondalite and one sample of metagabbro (Fig. 7a). Themetagranites exhibit high-K calc-alkaline composition, while thecharnockite, khondalite and tuffs reflect medium-K calc-alkaline fea-tures on K2O vs. SiO2 plot (Fig. 7b). In the SiO2 vs. Fe*/(Fe* +MgO) dia-gram (Fig. 7c), the charnockite falls in the magnesian field, consistentwith the Neoarchean charnockites of the Yinshan Block (Ma et al.,2013) and the post-collisional charnockites from the Chengde area ofTNCO (Yang et al., under review). The metagabbros show a prominent

Fig. 6. (a) SiO2 vs. Na2O+K2Odiagram. The compositional fields are after Le Bas et al. (1986). (b[Al2O3/(Na2O + K2O)] plots.The fields are after Maniar and Piccoli (1989).

tholeiitic to feeble calc-alkaline affinity and straddle the ferroan andmagnesian fields (Fig. 7c).

5.1.2. Trace and rare earth elementsThe metagabbros show a wide range in transitional trace element

compositions (Ni: 15.6–63.9 ppm; Cr: 4.6–70.4 ppm; Co: 23.9–60.9 ppm)whereas the tuffs andmetagranites have relatively lower con-centrations of these elements (Ni: 1.5–1.8 ppm, 3.9–6.4 ppm; Cr: 1.2–3.3 ppm, 3.7–24.5 ppm; Co: 0.5–1.1 ppm, 3.1–3.9 ppm). Charnockiteshows relatively higher concentrations of Ni, Cr and Co than thekhondalite (Ni: 50.9 and 17.7 ppm, Cr: 102.7 and 77.6 ppm and Co:25.5 and 8.2 ppm respectively). The studied samples are characterizedby distinct enrichment in large ion lithophile elements (LILE; Table 2).They exhibit prominent and variable LREE enrichment on chondrite nor-malized REE patterns [metagabbros (La/Sm)N = ~1.5–2.8; charnockite(La/Sm)N = 2.9; khondalite (La/Sm)N = 5.2; tuffs (La/Sm)N = ~11.7–12.0; metagranites (La/Sm)N = ~9.0–3.8], with relative depletion inHREE (especially in the metagranite OY-XH-1A and the two samples oftuffs OY-XH-9A and OY-XH-11) (Fig. 9a, c, e, g and i). Out of fourmetagabbro samples one shows a relatively flat REE pattern (Fig. 9e).One metagranite sample displays a positive Eu anomaly whereas theother shows a negative Eu anomaly suggesting plagioclase accumula-tion and fractionation respectively (Fig. 9a). The primitive mantle nor-malized trace element abundances for the metagranites (Fig. 9b)display positive Rb anomalies and negative anomalies at Nb and Ta.

) SiO2 vs. Zr/TiO2 diagram. (c) An–Ab–Or. (d) A/CNK [Al2O3/(CaO+Na2O+K2O)] vs. A/NK

Fig. 7. (a) Zr vs. Y plots (fields after Pearce and Norry, 1979). (b) SiO2 vs. K2O plots (fields after Rickwood, 1989). (c) Fe*/(Fe* + MgO) vs. SiO2 (fields after Frost et al., 2001).Late Archean charnockites from Ma et al., 2013 and post-collisional charnockites from Yang et al., under review.

Fig. 8. (a) Nb vs. Y diagram, (b) Rb vs. Y + Nb diagram and (c) Nb/Zr vs. Zr diagram.Fields after Pearce et al. (1984).



Besides, sample OY-XH-1A exhibits positive anomalies for Ba, Sr, Zr, andHf and negative anomalies for Th, Nd and Sm whereas OY-XH-12 con-trastingly exhibits negative anomalies for Ba, Sr, Zr, and Hf and positiveanomalies for Th, Sm and Nd. Sample OY-XH-1A displays greater HREE

Fig. 9. Chondrite-normalized REE patterns for (a) metagranites, (c) charnockite, (e) metagMcDonough (1989). Primitive mantle-normalized spider diagrams for (b) metagranites, (d) chPrimitive mantle values are after Sun and McDonough (1989).

depletion relative to OY-XH-12 (Fig. 9b). The charnockite (OY-XH-7A)shows similar mantle normalized multi-element patterns (Fig. 9d) tothe metagranites except negative anomalies at Rb. The metagabbrosshow enrichment in LILE (Rb and Ba) and depletion in HFSE (Th)

abbros, (g) tuffs and (i) khondalite. Chondrite normalization values are after Sun andarnockite, (f) metagabbros, (h) tuffs and (j) khondalite.

Fig. 9 (continued).


reflected in terms of negative Nb–Ta and Zr–Hf anomalies. These sam-ples show distinct negative Sr and Th anomalies (Fig. 9f). Sample OY-XH-1B displays diminished LREE and elevated HREE relative to theother metagabbro samples (Fig. 9f). The mantle normalized trace ele-ment abundance patterns for the tuffs aremarked by positive anomaliesfor Rb and K with negative anomalies at Ba, Th, Nb, Ta, Zr and Hf(Fig. 9h). Distinct negative anomalies are observed at Ce, sample OY-XH-11 exhibits positive anomalies for Ba and Sr whereas OY-XH-9Ashows negative Ba and Sr anomalies (Fig. 9h). The multi-element pat-terns of khondalite exhibit positive Rb, K, Zr andHf anomalies with neg-ative anomalies at Th, Nb and Ta (Fig. 9j).

5.2. Geochronology

Cathodoluminescence (CL) images of representative zircon grainsfrom the various rock types analyzed in this study are shown inFigs. 10–12 with the spot 207Pb/206Pb ages and εHf(t) values. The U–Pb analytical data from LA-ICPMS and SHRIMP dating are given in Sup-plementary Tables 3 and 4. The zircon U–Pb concordia plots and histo-grams with probability curves are show in Figs. 13–17.

5.2.1. MetagraniteZircons from themetagranite (sampleOY-XH-1A) showprismatic to

stumpymorphology, and few grains are partly rounded.Most of the zir-con grains from these samples are colorless and some are light brown-ish. The grains range from 100–200 × 30–80 μm in size with aspect

ratios of 3:1 to 1.2:1. In CL images, the zircons display clear oscillatoryzoning, with core–rim textures, suggesting magmatic origin followedby metamorphic overgrowth (Fig. 10a). The rims are too thin for U–Pbdating.

Sixteen spotswere analyzed on16 zircon grains (Table 3) and the re-sults show Pb contents of 31–616 ppm, U contents of 54–912 ppm andTh contents of 40–126 ppm (with spot 14 showing exceptionally highvalues of 2152 ppm of Pb, 1149 ppm of U and 534 ppm of Th) andhigh Th/U ratios of 0.14 to 4.39. The data define an intercept age of2410 ± 41 Ma (MSWD = 2.1, N = 16) (Fig. 13 a, b), and display207Pb/206Pb weight mean age of 2390 ± 20 Ma (MSWD = 1.4, N = 5)when calculated by using data with concordance higher than 95%.Based on the high Th/U ratios and clear oscillatory zoning of the zircongrains, the 2.4 Ga age is taken to represent the timing of emplacement ofthe granitoid magma.

5.2.2. CharnockiteMost of the zircon grains from the charnockite (sample OY-XH-7A)

show prismatic to stumpymorphology, and few grains are partly round-ed.Most grains are colorless and some are light brownish, ranging in sizefrom80–200 to 50–120 μmwith aspect ratios of 3:1 to 1:1 (with a fewupto 5:1). In CL images (Fig. 10b), all the zircon grains display clear oscilla-tory zoning and core–rim textures and carry low luminescence rimswhich are too thin for LA-ICPMS U–Pb analysis. They show complexstructures, corresponding to magmatic origin and later metamorphicoverprint, with a possible fluid-assisted late magmatic alteration.

Fig. 10. Cathodoluminescence (CL) images of representative zircon grains from metagranite OY-XH-1A (a), charnockite OY-XH-7A (b) and metagabbro IM13-18 (c). The values writtenagainst each grain represent the spot age in Ma (top) and the εHf(t) calculated for the 207Pb/206Pb mean age (bottom).


A total of 32 spots were analyzed on 32 zircon grains (Table 3) andthe results are divided into 3 groups: the first group contains 29 spotswhich show Pb content in the large range of 0.5 to 245 ppm, U contentin the range of 30 to 460 ppm and Th content in the range of 48 to1034 ppm, respectively, with high Th/U ratios of 1.40 to 3.04 (spot 37with Th/U ratio of 61.76 has been rejected). From the concordia dia-grams (Fig. 13 c, d), 28 of the 29 zircons (except spot 37) define anupper intercept age of 2.47 Ga which is identical to their 207Pb/206Pb

Fig. 11. Cathodoluminescence (CL) images of representative zircon grains from gabbros (a) IM1spot age in Ma (top) and the εHf(t) calculated for the 207Pb/206Pb mean age (bottom).

weightedmean age of 2446±11Ma (MSWD= 0.50, N=17). The sec-ond group including the two spots (Nos. 10 and 11) shows Pb contentsof 88 ppm and 124 ppm, U contents of 70 ppm and 93 ppm, and Th con-tents of 154 ppm and 215 ppm, respectively, with Th/U ratios of 0.43and 0.46. They show high concordance of 99%–100% and 207Pb/206Pbspot ages of 2389 ± 10 Ma and 2370 ± 10 Ma with the mean age of2381 Ma. The third group is defined by a single zircon (spot 13) withconcordance of 100%. The grain shows Pb content of 199 ppm,U content

3-19, (b) IM13-20 and (c) OY-XH-1B. The values written against each grain represent the

Fig. 12. Cathodoluminescence (CL) images of representative zircon grains from tuffs (a) OY-XH-9A and (b) OY-XH-11 and khondalite (c) OY-XH-3A. The values written against each grainrepresent the spot age in Ma (top) and the εHf(t) calculated for the 207Pb/206Pb mean age (bottom).

Fig. 13. Zircon U–Pb concordia plots (a) and age data histograms with probability curves (b) for the meta-granite sample OY-XH-1A. Zircon U–Pb concordia plots (c) and age data histo-grams with probability curves (d) for the charnockite sample OY-XH-7A.


Fig. 14. Zircon U–Pb concordia plots (a) and age data histogramswith probability curves (b) for themetagabbro sample IM13-18. Zircon U–Pb concordia plots (c) and age data histogramswith probability curves (d) for the metagabbro sample IM13-19.


of 205 ppm, and Th content of 372 ppm, with a Th/U ratio of 0.55 and a207Pb/206Pb age of 2208± 10Ma. The high Th/U ratios and clear oscilla-tory zoning of the older concordant group of zircons, suggest that the207Pb/206Pb weighted mean age of ca. 2.45 Ga represents the timing ofemplacement of the protolith magma. The 207Pb/206Pb weighted meanage of ca. 1.89 Ga suggests new zircon growth at this time from amajor thermal event, followed by recrystallization at ca. 1.85 Ga and1.75 Ga. The 2.45 Ga and 2.2 Ga ages mark magmatism and thermalevents.

5.2.3. MetagabbrosIn the cathodoluminescence (CL) images, the zircons from the

metagabbros (samples IM13-18, Fig. 10c; IM13-19, IM13-20 and OY-XH-1B, Fig. 11 a, b, c) display well-defined crystal morphology withprismatic shape and/or clear oscillatory zoning, suggesting a magmaticorigin. Most of them are colorless and some are light brownish, with asize range of 100–500 × 50–300 μm and aspect ratios of 3:1 to 1:1(some grains show up to 5:1 and 7:1). Many grains possess clearcore–rim textures with low luminescence rims of variable size rangessuggesting metamorphic overgrowth. Some of these show roundedshapes and complex structure or lacking any obvious internal features.

Twenty six zircon grains were analyzed from sample IM13-18. Theanalytical results are listed in Table 4 and plotted in the concordia dia-gram (Fig. 14a, b). The analytical data show a wide range of Pb (0.00–79%), U (6–88 ppm) and Th (3–72 ppm) with Th/U ratios of 0.37–1.05. The 207Pb/206Pb spot ages range from 1834 to 1962 Ma and yield207Pb/206Pb weighted mean age of 1900 ± 15 Ma (MSWD = 0.52,N = 26), close to the upper intercept age of 1909 ± 24 Ma(MSWD= 0.52, N = 26) (Fig. 14a, b).

Twenty five zircon grains were analyzed from sample IM13-19 forU–Pb age dating (Table 3) and the results are plotted in Fig. 14 c, d.The Pb, U and Th ranges of the zircons are 14–68 ppm, 37–167 ppmand 5–222 ppm, respectively, with high Th/U ratios of 0.93 to 1.60(with the exception of spot 22 showing low Th/U ratios of 0.06). Allthe spots cluster as a coherent group on the concordia (concordanceof 95%–100%, except spot 22 with a concordance of 92) with 207Pb/206Pb ages ranging from 1807 to 1935 Ma. The data yield 207Pb/206Pbweighted mean age of 1879 ± 12 Ma (MSWD = 0.59, N = 25)(Fig. 14c, d).

Thirty five zircon grains were analyzed from sample IM13-20(Table 3) and the results are plotted in Fig. 15 a, b. The Pb, U and Thranges of the zircons are 11–276 ppm, 31–676 ppm and 9–420 ppm, re-spectively, with high Th/U ratios of 0.27 to 1.02 (except spot 19 withlow Th/U ratios of 0.06). Twenty-nine spots cluster as a coherentgroup on the concordia (concordance of 92%–100%) with 207Pb/206Pbages ranging from 1913 to 1976Ma. The data yield 207Pb/206Pb weight-edmean age of 1944.3±6.6Ma (MSWD= 0.88, N=35), and anupperintercept age of 1946.2 ± 8.4 Ma (MSWD = 0.51, N = 35), which arevery close to the 207Pb/206Pb weighted mean age of 1947 ± 7 Ma(MSWD= 0.94, N = 29) from the concordia plots (Fig. 15a, b).

Thirty-seven zircon grains were analyzed from sample OY-XH-1B(Table 3) and the results are plotted in Fig. 15 c, d. The Pb, U and Thranges of the zircons are 8–207 ppm, 15–863 ppm and 2–96 ppm, re-spectively, with high Th/U ratios of up to 6.77. The data can be dividedinto 3 groups: one with an upper intercept age of 2476 ± 31 Ma andlower intercept age of 1752 ± 61 Ma (MSWD = 0.80, N = 32); thesecond with 207Pb/206Pb weighted mean age of 2125 ± 18 Ma(MSWD = 1.12, N = 3); the third showing the 207Pb/206Pb weighted

Fig. 15. Zircon U–Pb concordia plots (a) and age data histogramswith probability curves (b) for themetagabbro sample IM13-20. Zircon U–Pb concordia plots (c) and age data histogramswith probability curves (d) for the metagabbro sample OY-XH-1B.


mean age of 1852± 19Ma (MSWD= 0.112, N=4). These results sug-gest that the metagabbro was emplaced at ca. 2.5 Ga, followed by newzircon growth (as well as Pb loss in older zircons) during the thermalevent at 2.1 Ga, and recrystallization during the later thermal eventsat ca. 1.85 Ga and ca. 1.75 Ga.

The prismatic euhedral to subhedral grainmorphology,well-definedoscillatory zoning, and high Th/U ratios indicate that the zircon grainsfrom the metagabbros are of magmatic origin. Therefore, their 207Pb/206Pb weighted mean ages ranging from 2.5 to 1.9 Ga are interpretedas the emplacement ages followed by metamorphism at ca. 1.85 Ga.The youngest age of 1.75 Ga correlates with the post-collisional thermalevent recorded from this region (Yang et al., 2014a).

5.2.4. Felsic tuffsThe zircons from felsic volcanic tuffs in the study area (samples OY-

XH-9A and OY-XH-11) are markedly smaller in size (Fig. 12 a, b). Mostof them are smaller than 100 μm in length and 50 μm in width withaspect ratios of 2:1 to 1:1, with a few exceptions that show length of100–120 μm, width of 50–80 μm and aspect ratios of 4:1 to 1.5:1. InCL images, the zircons display very clear oscillatory zoning; someshow rounded shapes, whereas others display prismatic to stumpymorphology.

Twenty-eight spots were analyzed on 28 zircon grains (Table 3) andthe results show Pb, U and Th contents in the range of 252 to 441 ppm,151 to 259 ppm and 58 to 139 ppm, respectively, with high Th/U ratiosof 1.58 to 2.98. The data define an intercept age of 1907 ± 17 Ma(MSWD= 1.12, N=28)which is identical to their 207Pb/206Pbweight-ed mean age of 1901.2 ± 9.6 Ma (MSWD = 2.7, N = 28) (Fig. 16a, b).Thirty spots were analyzed on 30 zircon grains from the second sample

(OY-XH-11; Table 3) and the results show high Pb content of 162–501 ppm (even up to 1305 ppm), U content of 81 to 809 ppm and Thcontent of 41 to 180 ppm with high Th/U ratios of 0.62 to 7.63. All thespots define an intercept age of 1902 ± 17 Ma (MSWD = 1.8, N =30) which is identical to their 207Pb/206Pb weighted mean age of1904.4 ± 6.1 Ma (MSWD = 1.6, N = 20) (Fig. 16c, d). Based on thehigh Th/U ratios and clear oscillatory zoning of the zircon grains, the207Pb/206Pbweightedmean age of 1.90Ga is taken to present the timingof eruption of the felsic magma.

5.2.5. KhondaliteZircons from the khondalite sample (OY-XH-3A) are markedly

smaller in size than those in the charnockite and metagabbros(Fig. 12c). Most of them are smaller than 100 μm in length and 50 μmin width with aspect ratios of 2.5:1 to 1:1, with a few exceptions thatshow length of 100–120 μm, width of 50–80 μm and aspect ratios of2:1 to 1.5:1. The zircon grains show prismatic to stumpy morphology,and some grains are anhedral. In CL images, some of the zircons displayclear oscillatory zoning, and the others are structureless or show core–rim textures with very thin rims. Twenty spots were analyzed on 20 zir-con grains (Table 3) and the results show Pb content of 45–395 ppm, Ucontent of 104–435 ppm and Th content of 38–609 ppmand Th/U ratiosof 0.15 to 4.78. From their concordia plots (Fig. 16c, d), the 20 zirconscan be divided into two groups: the first set including 17 spots definesan intercept age of 2102 ± 76 Ma (MSWD = 3.3, N = 17); the othergroup shows the 207Pb/206Pb weighted mean age of 1881 ± 20 Ma(MSWD = 1.02, N = 3) (Fig. 17a, b). The ca. 2.1 Ga zircons were evi-dently derived from magmatic sources and were incorporated into the

Fig. 16. Zircon U–Pb concordia plots (a) and age data histogramswith probability curves (b) for themeta-tuff sample OY-XH-9A. Zircon U–Pb concordia plots (c) and age data histogramswith probability curves (d) for the meta-tuff sample OY-XH-11.


protolith sediments of these rocks, followed by metamorphism as ca.1.88 Ga.

5.3. Lu–Hf isotopes

A total of 81 zircon grains were analyzed for Lu–Hf isotopes on thesamedomains fromwhere theU–Pb age datawere gathered. The resultsare presented in Table 5 and plotted in Fig. 18. The Lu–Hf data on zirconsfrom the individual rock types are briefly discussed below.

Fig. 17. Zircon U–Pb concordia plots (a) and age data histograms w

5.3.1. MetagraniteSix zircon grains from sample OY-XH-1A were selected for Lu–Hf

isotopic analysis (Table 5). Calibrated to the crystallization age of2410 Ma (upper intercept age), the data show low initial 176Hf/177Hfvalues of 0.281239 to 0. and εHf(t) values of −0.2 to 2.6 (average of1.74), Hf depleted mantle model ages (TDM) of 2635 to 2744 Ma andHf crustal model ages (TDMC ) of 2774 to 2947 Ma. These results suggestthat themagma source involved Neoarchean juvenilemantle plus limit-ed reworked older crustal components.

ith probability curves (b) for the khondalite sample OY-XH-3A.

Table 5In situ Lu–Hf isotopic data of zircons from Xinghe and Jining, North China Craton.

No. Age (Ma) 176Yb/177Hf 176Lu/177Hf 176Hf/177Hf 2σ 176Hf/177Hfi εHf(0) εHf(t) TDM (Ma) TDMC (Ma) fLu/Hf

OY-XH-1A.4 2410 0.018476 0.0006 0.281346 0.000017 0.281318 −50.4 2.6 2635 2774 −0.98OY-XH-1A.12 2410 0.025644 0.000800 0.281276 0.000015 0.281239 −52.9 −0.2 2744 2947 −0.98OY-XH-1A.15 2410 0.019829 0.000635 0.281320 0.000014 0.281291 −51.4 1.6 2673 2834 −0.98OY-XH-1A.31 2410 0.023801 0.000592 0.281336 0.000017 0.281309 −50.8 2.3 2648 2794 −0.98OY-XH-1A.35 2410 0.026329 0.000658 0.281330 0.000017 0.281300 −51.0 1.9 2661 2814 −0.98OY-XH-1A.33 2410 0.023710 0.000585 0.281338 0.000018 0.281311 −50.7 2.3 2645 2790 −0.98OY-XH-1B.1 2480 0.013095 0.000340 0.281303 0.000018 0.281287 −51.9 3.1 2675 2797 −0.99OY-XH-1B.2 2480 0.007843 0.000215 0.281304 0.000021 0.281294 −51.9 3.3 2665 2782 −0.99OY-XH-1B.4 2480 0.011869 0.000310 0.281236 0.000018 0.281222 −54.3 0.8 2762 2939 −0.99OY-XH-1B.5 2480 0.011696 0.000299 0.281296 0.000021 0.281282 −52.2 2.9 2682 2809 −0.99OY-XH-1B.8 2480 0.015423 0.000377 0.281269 0.000017 0.281252 −53.1 1.8 2723 2874 −0.99OY-XH-1B.9 2480 0.011870 0.000295 0.281324 0.000017 0.281310 −51.2 3.9 2643 2746 −0.99OY-XH-1B.10 2480 0.011761 0.000291 0.281264 0.000021 0.281250 −53.3 1.8 2724 2877 −0.99OY-XH-1B.11 2480 0.015125 0.000371 0.281247 0.000017 0.281230 −53.9 1.0 2752 2922 −0.99OY-XH-1B.12 2480 0.020841 0.000473 0.281290 0.000020 0.281267 −52.4 2.4 2702 2840 −0.99OY-XH-1B.14 2480 0.022316 0.000520 0.281268 0.000020 0.281243 −53.2 1.5 2735 2892 −0.98OY-XH-1B.15 2125 0.001328 0.000032 0.281555 0.000019 0.281553 −43.1 4.4 2319 2442 −1.00OY-XH-1B.16 2480 0.009225 0.000230 0.281265 0.000020 0.281255 −53.3 1.9 2718 2868 −0.99OY-XH-1B.18 2480 0.022825 0.000598 0.281270 0.000020 0.281242 −53.1 1.5 2737 2895 −0.98OY-XH-1B.19 2480 0.021596 0.000558 0.281287 0.000020 0.281260 −52.5 2.1 2712 2855 −0.98OY-XH-1B.21 2480 0.019700 0.000524 0.281371 0.000019 0.281346 −49.5 5.2 2596 2668 −0.98OY-XH-1B.22 2480 0.006377 0.000191 0.281275 0.000018 0.281266 −53.0 2.3 2703 2844 −0.99OY-XH-1B.23 2480 0.015320 0.000467 0.281276 0.000014 0.281254 −52.9 1.9 2720 2870 −0.99OY-XH-1B.24 2480 0.017766 0.000571 0.281297 0.000015 0.281270 −52.1 2.5 2699 2833 −0.98OY-XH-1B.25 2480 0.009365 0.000292 0.281282 0.000015 0.281268 −52.7 2.4 2701 2839 −0.99OY-XH-1B.26 2480 0.012387 0.000369 0.281319 0.000016 0.281302 −51.4 3.6 2655 2765 −0.99OY-XH-1B.27 2480 0.015452 0.000492 0.281284 0.000014 0.281260 −52.6 2.1 2712 2855 −0.99OY-XH-1B.28 2480 0.014839 0.000444 0.281299 0.000015 0.281278 −52.1 2.8 2688 2817 −0.99OY-XH-1B.31 2480 0.018195 0.000512 0.281326 0.000019 0.281302 −51.1 3.6 2656 2765 −0.98OY-XH-1B.32 1852 0.009426 0.000251 0.281262 0.000019 0.281253 −53.4 −12.5 2724 3273 −0.99OY-XH-1B.33 2480 0.011327 0.000300 0.281286 0.000016 0.281272 −52.5 2.6 2695 2830 −0.99OY-XH-1B.39 2480 0.012231 0.000311 0.281319 0.000023 0.281304 −51.4 3.7 2652 2760 −0.99OY-XH-1B.40 2480 0.006121 0.000180 0.281290 0.000020 0.281282 −52.4 2.9 2681 2809 −0.99OY-XH-3A.6 2102 0.021591 0.000703 0.281617 0.000015 0.281589 −40.8 5.1 2274 2378 −0.98OY-XH-3A.13 2102 0.009722 0.000236 0.281477 0.000016 0.281468 −45.8 0.8 2434 2644 −0.99OY-XH-3A.30 2102 0.001551 0.000036 0.281540 0.000015 0.281538 −43.6 3.3 2338 2490 −1.00OY-XH-3A.38 1881 0.001375 0.000024 0.281534 0.000015 0.281534 −43.8 −1.9 2345 2642 −1.00OY-XH-7A.1 2446 0.032251 0.000951 0.281307 0.000023 0.281263 −51.8 1.4 2712 2871 −0.97OY-XH-7A.2 2446 0.025880 0.000760 0.281337 0.000024 0.281302 −50.7 2.8 2658 2787 −0.98OY-XH-7A.3 2446 0.026702 0.000755 0.281302 0.000026 0.281267 −52.0 1.6 2705 2863 −0.98OY-XH-7A.4 2446 0.012390 0.000363 0.281328 0.000022 0.281311 −51.1 3.2 2643 2766 −0.99OY-XH-7A.6 2446 0.019596 0.000567 0.281327 0.000024 0.281300 −51.1 2.8 2659 2790 −0.98OY-XH-7A.8 2446 0.028082 0.000816 0.281379 0.000024 0.281341 −49.3 4.2 2605 2701 −0.98OY-XH-7A.14 2446 0.019236 0.000689 0.281302 0.000017 0.281269 −52.0 1.7 2701 2857 −0.98OY-XH-7A.19 2446 0.024234 0.000826 0.281340 0.000020 0.281301 −50.7 2.8 2659 2788 −0.98OY-XH-7A.21 2446 0.025487 0.000837 0.281313 0.000018 0.281274 −51.6 1.8 2695 2846 −0.97OY-XH-7A.23 2446 0.021334 0.000637 0.281281 0.000019 0.281251 −52.7 1.0 2726 2897 −0.98OY-XH-7A.25 2446 0.007606 0.000247 0.281312 0.000019 0.281301 −51.6 2.8 2656 2789 −0.99OY-XH-7A.26 2446 0.028934 0.000829 0.281310 0.000020 0.281271 −51.7 1.7 2699 2853 −0.98OY-XH-7A.33 2446 0.030142 0.000888 0.281286 0.000025 0.281244 −52.6 0.8 2737 2912 −0.97OY-XH-7A.37 2446 0.001409 0.000040 0.281415 0.000015 0.281413 −48.0 6.8 2505 2543 −1.00OY-XH-7A.46 2446 0.016060 0.000502 0.281244 0.000022 0.281220 −54.1 −0.1 2766 2965 −0.98OY-XH-7A.47 2446 0.017401 0.000548 0.281372 0.000021 0.281346 −49.5 4.4 2597 2690 −0.98OY-XH-9A.1 1901.2 0.021225 0.000633 0.281570 0.000015 0.281547 −42.5 −1.0 2334 2600 −0.98OY-XH-9A.3 1901.2 0.032499 0.000921 0.281558 0.000013 0.281524 −42.9 −1.8 2368 2649 −0.97OY-XH-9A.15 1901.2 0.018381 0.000541 0.281568 0.000013 0.281549 −42.6 −0.9 2331 2596 −0.98OY-XH-9A.25 1901.2 0.016691 0.000428 0.281631 0.000016 0.281616 −40.3 1.5 2238 2449 −0.99OY-XH-9A.34 1901.2 0.026991 0.000626 0.281626 0.000018 0.281603 −40.5 1.0 2257 2476 −0.98OY-XH-9A.37 1901.2 0.012520 0.000287 0.281589 0.000016 0.281579 −41.8 0.2 2287 2530 −0.99OY-XH-9A.39 1901.2 0.015761 0.000362 0.281554 0.000016 0.281541 −43.1 −1.2 2339 2613 −0.99OY-XH-9A.40 1901.2 0.054309 0.001225 0.281628 0.000018 0.281584 −40.5 0.4 2290 2518 −0.96OY-XH-9A.42 1901.2 0.020438 0.000493 0.281545 0.000016 0.281528 −43.4 −1.6 2359 2642 −0.99OY-XH-11.1 1904.4 0.016968 0.000439 0.281676 0.000020 0.281660 −38.8 3.1 2178 2349 −0.99OY-XH-11.21 1904.4 0.008809 0.000222 0.281571 0.000015 0.281563 −42.5 −0.3 2308 2563 −0.99OY-XH-11.23 1904.4 0.006585 0.000169 0.281569 0.000015 0.281563 −42.5 −0.3 2307 2562 −0.99OY-XH-11.26 1904.4 0.015831 0.000417 0.281615 0.000015 0.281599 −40.9 1.0 2260 2482 −0.99OY-XH-11.35 1904.4 0.005974 0.000151 0.281574 0.000014 0.281568 −42.4 −0.1 2300 2550 −1.00IM13.20.9 1944.3 0.012845 0.000309 0.281562 0.000025 0.281551 −42.8 0.2 2325 2563 −0.99IM13.20.18 1944.3 0.012276 0.000387 0.281563 0.000017 0.281548 −42.8 0.1 2329 2569 −0.99IM13.20.19 1944.3 0.019633 0.000613 0.281575 0.000015 0.281553 −42.3 0.2 2325 2559 −0.98IM13.20.20 1944.3 0.031798 0.000954 0.281567 0.000014 0.281532 −42.6 −0.5 2357 2604 −0.97IM13.20.23 1944.3 0.023910 0.000707 0.281612 0.000015 0.281586 −41.0 1.4 2281 2486 −0.98IM13.20.24 1944.3 0.032903 0.000986 0.281593 0.000018 0.281557 −41.7 0.4 2323 2550 −0.97IM13.20.25 1944.3 0.015838 0.000480 0.281614 0.000016 0.281597 −40.9 1.8 2264 2463 −0.99IM13.20.29 1944.3 0.013406 0.000394 0.281600 0.000015 0.281585 −41.5 1.4 2279 2488 −0.99

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Table 5 (continued)

No. Age (Ma) 176Yb/177Hf 176Lu/177Hf 176Hf/177Hf 2σ 176Hf/177Hfi εHf(0) εHf(t) TDM (Ma) TDMC (Ma) fLu/Hf

IM13.20.30 1944.3 0.031810 0.000891 0.281627 0.000018 0.281594 −40.5 1.7 2272 2469 −0.97IM13.20.31 1944.3 0.028176 0.000781 0.281608 0.000018 0.281580 −41.1 1.2 2290 2500 −0.98IM13.20.33 1944.3 0.037364 0.000978 0.281691 0.000021 0.281655 −38.2 3.9 2188 2334 −0.97IM13.20.35 1944.3 0.025671 0.000638 0.281644 0.000018 0.281620 −39.9 2.6 2234 2412 −0.98IM13.20.36 1944.3 0.012301 0.000291 0.281543 0.000020 0.281532 −43.5 −0.5 2350 2605 −0.99IM13.20.42 1944.3 0.035306 0.000822 0.281618 0.000019 0.281588 −40.8 1.5 2279 2482 −0.98


5.3.2. CharnockiteSixteen zircon domains were analyzed for Lu–Hf isotopes from sam-

ple OY-XH-7A (Table 5) where U–Pb age dating was done. Twenty-fivespots show initial 176Hf/177Hf values of 0.281220 to 0. 281413 and pos-itive εHf(t) values of 0.8 to 6.8 (except spot 46 with an εHf(t) value of−0.1, mean 2.48), respectively, with Hf depleted mantle model ages(TDM) of 2505 to 2766 Ma and Hf crustal model ages (TDMC ) of 2543 to2965 Ma when computed for the upper intercept age of 2446 Ma. Thedata from the charnockite suggest that the magma source mainly in-volved juvenile mantle components and limited reworked ancientcrustal components (Fig. 18).

5.3.3. MetagabbrosFourteen zircon grains were chosen for Lu–Hf isotopes from

metagabbro sample IM13-20 (Table 5). Corrected to the crystallizationages of 1944.3 Ma, the data show tight range initial 176Hf/177Hf valuesof 0.281532 to 281655 and dominantly positive εHf(t) values of −0.5to 3.9 (average of 1.10), respectively, with Hf depleted mantle modelages (TDM) of 2188 to 2357 Ma and Hf crustal model ages (TDMC ) of2334 to 2605 Ma.

Twenty-seven zircon domains were analyzed for Lu–Hf isotopesfrom sample OY-XH-1B (Table 5). Twenty-five zircon domainswere cal-culated for the crystallization ages of 2480 Ma (upper intercept age),and show initial 176Hf/177Hf and εHf(t) values of 0.281222 to 0.281346 and 0.8 to 5.2 (mean 2.54), respectively, with Hf depleted man-tle model ages (TDM) of 2596 to 2762 Ma and Hf crustal model ages(TDMC ) of 2668 to 2939 Ma. One zircon domain computed for its crystal-lization age of 2125 Ma, shows an initial 176Hf/177Hf value of 0.281553and εHf(t) value of 4.4 with Hf depleted mantle model ages (TDM) of2319 Ma and Hf crustal model ages (TDMC ) of 2442 Ma. The other zircondomain yields an initial 176Hf/177Hf value of 0.281253 and εHf(t) valueof −12.5 with Hf depleted mantle model ages (TDM) of 2724 Ma andHf crustal model ages (TDMC ) of 3273Ma, when calculated for its crystal-lization age of 1852 Ma.

The data from the metagabbros suggest that the magma source in-volved a mixture of juvenile mantle input and reworked ancient crustalcomponents (Fig. 18), typical of continental arc magmatism.

Fig. 18. εHf(t) versus 207Pb/206Pb mean age diagram of zircons from the metagranite,charnockite, gabbros, meta-tuffs and khondalite.

5.3.4. Felsic tuffA total of nine zirconswere analyzed for Lu–Hf isotopes from sample

OY-XH-9A (Table 5). The data show initial 176Hf/177Hf and εHf(t) valuesof 0.281524 to 0. 281616 and −1.8 to 1.5 (mean −0.37), respectively,and Hf depleted mantle model ages (TDM) of 2238 to 2368 Ma and Hfcrustal model ages (TDMC ) of 2449 to 2649 Ma, when calculated at thecrystallization age of 1901 Ma. Five zircon domains were analyzed forLu–Hf isotopes from sample OY-XH-11 (Table 5). When calculated atthe crystallization age of 1904 Ma, the data yield initial 176Hf/177Hfand εHf(t) values of 0.281563 to 0. 281660 and −0.3 to 3.1 (averageof 0.7), respectively, with Hf depleted mantle model ages (TDM) of2178 to 2308 Ma and Hf crustal model ages (TDMC ) of 2349 to2563 Ma. The data from felsic tuffs suggest that the magma sourceinvolved mainly juvenile mantle and reworked ancient crustalcomponents (Fig. 18).

5.3.5. KhondaliteOnly four zircon domains were analyzed for Lu–Hf isotopes from

sample OY-XH-3A (Table 5) on domains where U–Pb age dating wasdone, due to the small size of the zircon grains. Three spots, calculatedfor the crystallization age of 2102Ma (upper intercept age), show initial176Hf/177Hf and εHf(t) values of 0.281468 to 0. 281589 and 0.8 to 5.1(mean 3.10), respectively, with Hf depleted mantle model ages (TDM)of 2274 to 2434 Ma and Hf crustal model ages (TDMC ) of 2378 to2644 Ma. The remaining one zircon grain shows initial 176Hf/177Hf andεHf(t) values of 0.281534 and −1.9, respectively, with Hf depletedmantle model ages (TDM) of 2345 Ma and Hf crustal model ages (TDMC )of 2642 Ma, when calculated for the crystallization age of 1881 Ma.The data from the khondalite suggest that zircons in the sedimentaryprotolith were derived frommagmas generated through the reworkingof older crustal basement, together with the input of juvenile mantlecomponents, as in the case of the other magmatic units describedabove (Fig. 18).

6. Discussion

6.1. Evidence for Paleoproterozoic arc magmatism in the NCC

Previous studies have indicated that the earliest arc-related mag-matic event in the TNCO took place at ca. 2.5 Ga ago (e.g., Zhao et al.,2008; Wilde et al., 2005; and references therein). The magmatism gen-erated both intrusive and extrusive suites that are now distributedwithin the low-grade granite–greenstone terranes such as those in theWutai granite–greenstone belt. According toWang et al. (2004) thema-jority of 2530–2515 Ma mafic volcanic rocks in the Wutai Group werederived from arc-type basalts. Kröner et al. (2005a,b) suggested thatthe 2520–2445 Ma TTG gneiss in the Hengshan and Fuping terraneswere modified by subduction components, and that the wide range inSiO2 content, high Na2O, Ba, and Sr and low Y and HREE, and the selec-tive enrichment in LILE and depletion in Nb, Ta and Ti correlate withmantle-derived magmatic precursors. Wan et al. (2000) and Genget al. (2000) showed that the 2199–2173 Ma Chijianling–Guandishangneisses are characterized by calc-alkaline signature and have arc affin-ities. The Paleoproterozoicmagmatic event is alsowidely represented in


other complexes in the TNCO including the Zhongtiao Complex fromwhere Sun et al. (1992) reported a single-grain zircon age of 2321 ±2 Ma in granitoid gneiss, and from the Hengshan Complex from whereKröner et al. (2005a,b) identified granitoid emplacement between2360 Ma and 2330 Ma. Zhao et al. (2008) reported SHRIMP zircon U–Pb ages from tonalitic, granodioritic and monzogranitic plutons fromthe Chijianling–Guandishan gneisses which show emplacement agesof 2199±11Ma, 2180±7Maand 2173±7Ma, respectively. Granitoidgneisses of similar ages have also been reported from other complexesin the TNCO such as the Hengshan Complex with magmatic pulses at2200–2100 Ma (Kröner et al., 2005a), and the Nanying granitoids ofthe Fuping Complex with ages of 2109 ± 5 Ma, 2097 ± 6 Ma and2097 ± 46 Ma (Guan et al., 2002; Zhao et al., 2002). Paleoproterozoicgranitoids in the low-grade Wutai Complex represented by theDawaliang pluton (2176 ± 12 Ma) and the Wangji-ahui pluton(2117± 17Ma, 2116± 16Ma and 2084 ± 20 Ma) are other examples(Wilde et al., 2005). Zhao et al. (2008) and Liu et al. (2012) presentedU–Pb zircon data from various units in the Lüliang Complex at thewesternmargin of the TNCO. The TTG gneisses with calc-alkaline chemistry andmagmatic arc affinity in this complex were emplaced at ca. 2.5 Ga,representing the earliest arc-related magmatic event, followed by arc-related magmatic pulses as 2.4 and 2.2 Ga. Metamorphism associatedwith collision occurred at ca. 1.87 Ga. Subsequently, a series of post col-lisional granitoids including porphyritic granite, charnockite, and mas-sive granite were emplaced during 1.83 to 1.79 Ga. Liu et al. (2012)reported geochemical and zircon U–Pb data from metavolcanic unitsin the Yejishan and Lüliang groups of the Lüliang Complex which illus-trate active continental margin arc magmatism at 2.2 Ga, followed bymetamorphism during 1.90–1.83 Ga associated with the collisionalevent, and post-collisional extension at 1.80 Ga.

Paleoproterozoic magmatism has also been reported from thesouthern margin of the NCC. Zhou et al. (2014) investigated potassicgranites from the Lushan area and reported zircon U–Pb ages of 2.2 Gaand zircon εHf(t) values of −2.4 to +7.3 with TDMC varying between2848 and 2306 Ma. Although these authors favored intra-continentalrifting for the magma genesis, when we replotted their geochemicaldata in relevant discrimination diagrams, a distinct volcanic arc graniteaffinity is revealed, suggesting arc magmatic affinity and subduction-related setting at ca. 2.2 Ga.

The suite of granitoids, charnockites, gabbros, felsic volcanic tuffsand khondalites reported in our study from the Xinghe and Jiningareas along the junction between the IMSZ and the TNCO, two of themajor subduction–collision zones in the NCC, suggest prominentarc magmatic and related felsic volcanic episodes associated withPaleoproterozoic convergent margin tectonics in the NCC. Similar arcmagmatic suites of charnockite–granite–gabbro–felsic tuff associationhave been reported from several regions elsewhere on the globe includ-ing the Mesoarchean Coorg Block (Santosh et al., 2013a) and theNeoarchean Nilgiri Block (Praveen et al., 2013; Samuel et al., 2014) insouthern India, formed in subduction-related active continental marginsettings.

The salient geochemical features of these rocks are also suggestive ofsubduction-related arc magmatic settings. In the Zr/TiO2 verse SiO2 dia-gram (Fig. 6b), the khondalites and felsic tuffs show rhyodacite to dacitecompositions, similar to felsic volcanic rocks in active continental mar-gins. In the Zr–Y diagram, all the rocks are plotted in the area of calc-alkaline to tholeiitic affinities (Fig. 7a), typical of rock suites formed incontinental arcs in other Precambrian terranes (e.g., Santosh et al.,2013b). In the Y–Nb diagram (Fig. 8a), the majority of these rocks areplotted in the VAG + syn-COLG, and in the Y + Nb vs. Rb diagram,they fall in the VAG area (Fig. 8b). In the Nb/Zr vs. Zr diagram, all theplots fall in the field of rocks generated in subduction setting (exceptonemetagabbroic rock IM13-18; Fig. 8c). The trace element distributionpatterns (Fig. 9) are broadly consistent with magma processes and inconvergent settings. The LILE and LREE enrichment in the majoritysamples and relative HFSE depletion might suggest dehydration of

subducted oceanic lithosphere and influx of fluid mobile elements intothe mantle wedge through metasomatic processes (Manikyambaet al., in press). The moderate REE fractionation trends might suggesta heterogeneous sourcemarked by subduction-derived arc componentswith minor input from continental crust. The geochemical features ofthe magmatic suite are consistent with their derivation in a continentalarc related to an active continental margin, similar to the featuresdisplayed by the arc magmatic suite in the Paleoproterozoic LüliangComplex within the TNCO (Liu et al., 2010; Liu et al., 2012).

Among the two compositional varieties of charnockites as ferroanand magnesian (Frost and Frost, 2008; Rajesh and Santosh, 2012), thecharnockite of the present study classifies asmagnesian variety.Magne-sian charnockites are in general considered to have formed in asubduction setting (e.g. Rajesh, 2012; Santosh et al., 2013a). In Fig. 7c,the charnockites from theNCC including thepresent study and those re-ported in previous works (Ma et al., 2013; Yang et al., under review) arecharacterized by medium-K content, and calc-alkaline, metaluminousaffinities. The compositional characteristics of the magnesiancharnockite including the medium K contents and positive zircon εHfvalues (0.8 to 6.8, average 2.48, except one plot with an εHf value of−0.1) are consistent with magma generation from juvenile sources inarc setting. The presence of Neoarchean and Paleoproterozoic arc com-ponents associated with the subduction–accretion history has beenwidely identified in the NCC (e.g., Zhai and Santosh, 2011; Santoshet al., 2013a; Yang et al., 2014a). The geochemical features of the mag-nesian charnockites including their immobile trace element-based tec-tonic discrimination plots (Fig. 8) are also consistent with subduction-related arc signature.

The volcanic tuffs in our study are compositionally similar torhyodacites and dacites. The formation of rhyolitic rocks in an activecontinental margin can occur through: (i) direct melting of basalt pro-ducing extremely fractionated REE patterns and high Al2O3; (ii) asingle-stage melting of a sialic source resulting in an LREE-enriched liq-uid; and (iii) fractional crystallization of a basaltic magma giving rise toa low K2O rhyolitic melt (Edwards and Hodder, 1991; Manikyambaet al., 2012). The medium to low K2O contents (2.04–2.27 wt.%), andmoderate Al2O3 (12.01–13.54 wt.%) contents, and limited fraction ofLREE/HREE suggest that these rocks might have been derived by thefractional crystallization of basaltic magma. The majority of zircons inthese rocks display positive εHf(t) values (up to 3.1), suggesting domi-nantly juvenile source, with limited input from reworked crustalsources. Their petrogenetic features are consistent with formation inan active continental margin arc environment. In a recent study, Danet al. (2012) reported the results of SIMS U–Pb age and Hf–O isotopesin detrital zircons from khondalites and associated granitoid suite ofthe Helanshan Complex in the westernmost part of the KhondaliteBelt within the IMSZ. Their study suggested that the protoliths of theHelanshan khondalites were sourced from a provenance that witnessedprolonged, episodicmagmatism of ca. 2.18 Ga, 2.14 Ga, 2.09 Ga, 2.06 Ga,2.03 Ga and 2.00 Ga. The εHf(t) values show a range of +8.9 to −2.9andHf TDMC model ages between2.8 and2.1 Ga. The zirconHf–O isotopicdata (with δ18O peaks at 6.6‰ and 8.2‰) indicate that both juvenile andancient crustal components were involved in their source rocks. Danet al. (2012) therefore concluded that the protoliths of the Helanshankhondalite were sourced from a ca. 2.18–2.00 Ga continental arc withinan active continental margin. The volcanic tuffs reported in our studywith ca. 1.9 Ga magmatic zircons characterized by dominantly positiveεHf(t) values compare with the data from Helanshan khondalites re-ported by Dan et al. (2012), and might define the latest phase of conti-nental arc volcanism prior to the cessation of subduction and finalcollision in the NCC.

6.2. Tectonic implications

Our zircon U–Pb geochronological data show new zircon growthduring multiple tectonothermal events as inferred from 207Pb/206Pb


weighted mean ages of 2410 ± 41 Ma for the metagranite, 2480 ±12 Ma and 2125 ± 18 Ma from metagabbro sample OY-XH-1B,1946± 8Ma, 1900± 15Ma and 1879± 12Ma frommetagabbro sam-ples IM13-20, IM13-18 and IM13-19 respectively, 2446 ± 11 Ma fromthe charnockite, and 1904 ± 6 Ma and 1901 ± 9 Ma for metatuffs.The 207Pb/206Pb upper intercept age of zircons in the khondaliteshows 2102 ± 76 Ma which is identical to the age obtained from themagmatic zircons in one of the metagabbros (OY-XH-1B). Thekhondalites also carry a group of concordant metamorphic zirconswith 207Pb/206Pb mean age of 1881 ± 20 Ma. Metamorphic zircons inthe gabbros and charnockites also yield similar metamorphic ages of1890 ± 14 Ma and 1852 ± 19 Ma, respectively. The age data suggestprolonged 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 associat-edwith thefinal collision. Lu–Hf analyses reveal that the dominant pop-ulations of zircons from all the rock types are characterized by positiveεHf values (−1.9 to 6.8; mean 1.8; except one spot with the εHf valueof −12.5) (Fig. 19, Table 3). The εHf and TDMC data suggest that themagmas were mostly derived from Neoarchean and Paleoproterozoicjuvenile components.

Based on a global evaluation of Paleo-Mesoproterozoic magmaticarcs, Zhao et al. (2008) identified a major arc magmatic zone extendingfrom Arizona, through Colorado, Michigan, southern Greenland, Scot-land, Sweden and Finland, to western Russia, bordering the presentsouthern margin of North America, Greenland and Baltica (e.g., Goweret al., 1990; Karlstrom et al., 2001; Zhao et al., 2008). This zonewas cor-related to subduction-related episodic outgrowth along the continentalmargin of the supercontinent Columbia (Zhao et al., 2008; and refer-ences therein).

The results presented in this study, together with those from previ-ous investigations in different domains of the IMSZ and TNCO suggestmajor Paleoproterozoic arcmagmatic events in theNCC lasting for near-ly 600 million years associated with the final assembly of the crustalblocks into a coherent craton. Similar age spans have been observed insome of the major orogenic belts that went through prolongedsubduction–accretion–collision history, such as the Central AsianOrogenic Belt (e.g., Xiao and Santosh, 2014). The final cratonic archi-tecture of the NCC thus witnessed not only the arc–continent amal-gamations at 2.7–2.5 Ga (e.g., Zhai and Santosh, 2011; Geng et al.,2012), but also major crust building events in the Paleoproterozoicthrough juvenile and recycled components in continental magmaticarc systems along active convergent margin, followed by intensedeformation and metamorphism during the final collision stage at

Fig. 19. Tectonic framework of the central and northern parts of the North China Craton showiSuture Zone and the Trans-North China Orogen. See text for discussion and related references.

1.85–1.80 Ga. The magmatic pulses continued during the post-collision extension at 1.78 to 1.68 Ga.

In Fig. 19, we compile the major Paleoproterozoic magmatic recordin the IMSZ and the TNCO. In the Helanshan area of IMSZ, the continen-tal arc volcanics (khondalites) show magmatic ages of 2.18–2.00 Ga(Dan et al., 2012). In theHalaqin area, the volcanic rocks yieldmagmaticages of 1.90 Ga (Peng et al., 2011). In the Wulashan–Daqingshan area,the meta-mafic rocks show multiple magmatic ages of 2.50–2.45 Ga,2.30–2.10 Ga and 1.97–1.93 Ga (Wan et al., 2013; Liu et al., 2014). Inthe Tuguiwula area, the timing of mafic magmatism age is constrainedas 1.96–1.92 Ga (Peng et al., 2010). In the present study, our data fromgranitoids, charnockite, gabbro, felsic volcanic tuffs and khondaliteshow magmatism between 2.48 and 1.9 Ga in the Jining and Xingheareas. In the Xuanhua and Huai'an complexes, the TTG gneisses showthe magmatism ages of 2.52–2.47 Ga (Guan et al., 2002; Kröner et al.,2005a,b). In theHengshan complex, the various rock types showmultiplemagmatic ages of 2.52–2.44 Ga, 2.36–2.33 Ga, 2.2–2.1 Ga (Kröner et al.,2005a,b). In the Wutai complex, major magmatic pulses occurred at2.53–2.51 Ga and 2.35–2.08 Ga (Wang et al., 2004; Wilde et al., 2005;Wei et al., 2014), similar to the ages (2.52–2.44 Ga, 2.35–2.00 Ga) in theFuping and Zanhuang complexes (Guan et al., 2002; Zhao et al., 2002;Deng et al., 2013;Wei et al., 2014). In the Lüliang Complex, the granitoidswere emplaced at 2.50 Ga, 2.37 Ga and 2.20–2.17 Ga (Zhao et al., 2008).

The early Proterozoic Era, termed as the Siderian interval (2.5 to2.3 Ga, Plumb, 1991) has been considered as a relatively quiescent peri-od of juvenilemagmatismas tracked fromdetrital zircon record (Condieet al., 2009). The magmatic quiescence has been correlated to plate tec-tonic shutdown followingwidespread lithospheric stagnation andman-tle overturn (Condie, 1998; Condie et al., 2009). However, recent studies(Pehrsson et al., 2013, 2014) have revealed prominent record of orogen-esis in cratons and cratonic fragments from various parts of the worldduring the Siderian quiet interval. Examples include the 2.5–2.43 GaSleafordian of South Australia, the 2.49–2.43 Ga subduction–accretionorogens along the southern margin of the Dharwar craton in India, the2.45–2.4 Ga Selway terrane in NW Wyoming, the 2.45–2.35 GaArrowsmith of Arctic Canada, and the 2.35–2.30Ga Borboremaprovinceof Brazil, among other examples (Pehrsson et al., 2014). As discussedabove, the North China Craton preserves excellent records of earlyPaleoproterozoic arc magmatic events in several locations along theIMSZ and the TNCO suggesting vigorous plate tectonic processes alongactive convergent margins. Our results thus confirm the view ofPehrsson et al. (2014) and suggest that therewas no global plate tecton-ic shutdown during the Siderian quiet interval.

ng a compilation of the Paleoproterozoic ages frommagmatic suites in the Inner Mongolia


7. Conclusions

1. The granitoid–charnockite–gabbro–felsic tuff–khondalite suite ofrocks reported in this study from the confluence of the two majorPaleoproterozoic suture zones in the North China Craton representproducts of arc magmatism in a convergent margin setting duringthe Paleoproterozoic.

2. Our new data show the 207Pb/206Pb weighted mean ages of 2410 ±41 Ma for metagranite, 2480 ± 12 Ma, 2125 ± 18 Ma, 1946 ±8 Ma, 1900 ± 15 Ma and 1879 ± 12 Ma from metagabbros,2446 ± 11 Ma from charnockite, 1904 ± 6 Ma and 1901 ± 9 Mafor metatuffs, and the zircon 207Pb/206Pb upper intercept age of2102 ± 76 Ma in the khondalite correlate with major magmaticpulses. Metamorphic zircons from 207Pb/206Pb mean age of 1881 ±20 Ma from the khondalite and 1890 ± 14 Ma and 1852 ± 19 Mafrom the gabbros correlate with the final stage of collision.

3. The age data suggest prolonged arcmagmatism in a convergentmar-gin setting during ca. 2.48 to 1.9 Ga. The dominantly positive εHfvalues (−1.9 to 6.8;mean 1.8) suggest that themagmasweremostlyderived fromNeoarchean andPaleoproterozoic juvenile components.

4. The geochemical features also attest to subduction-related originwith a heterogeneous source marked by subduction-derived arccomponents and minor input from continental crust.

5. The Paleoproterozoic magmatic events in the NCC lasted for nearly600 million years and is proposed here as a major contributor tothe crust building events through juvenile and recycled componentsin a continental magmatic arc system. The data also suggest thatthere was no global plate tectonic shutdown during the Siderian pe-riod, and that active convergentmargin magmatism and crust build-ing occurred throughout Paleoproterozoic.

Supplementary Tables 3 and 4 can be found in the online version ofthe journal at http://dx.doi.org/10.1016/j.gr.2014.08.005.

Acknowledgments

We thank Prof. S. Kwon, Associate Editor and the two referees fromthe journal for their constructive commentswhich improved this paper.This study forms part of the PhD research of Qiong-yan Yang at theChina University of Geosciences Beijing. It also contributes to the TalentAward to M. Santosh under the 1000 Plan from the Chinese Govern-ment. We thank Xueming Teng for his help during field work and anal-yses. We also thank Jianzhen Geng (Tianjin Institute of Geology andMineral Resources), Hangqiang Xie and Prof. Alfred Kröner (BeijingSHRIMP Centre), Haihong Chen (China University of Geosciences),Hong Qin (China University of Geosciences Beijing), and Fang Ma(Peking University) for their help during the analysis.

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