Romanian Journal of

MINERAL DEPOSITS

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ISSN 12Z0-(;G-I 8

Geodynamics and Ore Deposit Evolution

VoI. 79 S uppl. 2

of the Alpine-Balkan-Carpathian-Dinaride Provin ce

ABel) - GEOD[ 2001 wonKSHOP VA TA BAI, nOMANIA

8 - 12 Junc, 2001

ABSTRACTS VOLUME Bucharest, 2001

11l,.; t.iillrlll G (·o lugi,· ,II Il' )III<Î IIÎ . , j

DII "lIl' l'~ li 2001

35

PROPYLlT IC ALT ERATION ASSOCIATE D WITH MINE RALlZATION IN THE APUSEN I MO UNTAINS

David Alderton DepI ofGeology, Royal Holloway (Universily of London), Egham, Surrey TW20 OEX, UK

I\l in eralogica l aud geochemical studies of propylitic :tlte ration assemblages In the Apuseni M ountains suggest Ihat the fluid s causing the propylitization had 'epithermal' characteristicsis. T he widespread propylitic alleration of the andesites in thi s region was caused by hydrothermal flu ids with P-T-X charac teristics which were essentially similar to thase ",hieh form ed Ihe abundant epilh erma l, precious metal mineraliza t ion.

P ropylitic a llera tion Propylitic alterat ion is common in the peripheral pans of many porphyry copper and epithermal. precious-metal vein systems However, studies of hydrothermal aheration have tended ta neglect this alteration fac ies and have instead concentrated on the alteration processes more directly associated ' with the mineralized systems. Studies of propylitic alteration associated with porphyry copper and epithermal, precious-metal, mineralization in the Apuseni Moumains of westem Romania are being conducted as pan of a larger study of the hydrothermal systems in this region

Mineralogy and Geochemistry Propylitized andesites in the area are characterized by the presence of chlorite, calcite, quartz, titanite, pyrite and (low Ti) magnetite. plus minor amoums of sericite, albite (?), kaolinite, apatite and al\anite, Chemical compositions of propylitized rocks demonstrate that only minor changes in the concentrations ofmost elements have occurred. Calcite: Carbon and oxygen isolopes of calcite are in the range 0 13C= -3 .3 to -7.5%0 POB and '- 180 = 126 to 21.3 %o SMOW, and as such are very similar ta values recorded for carbonates from the ~recious metal - bearing veins Strontium isotope compositions of calcite are in the range 87 6 Sr = 0.704900 to 0 .707700. This range lies between the values for unaltered andesite, and thase for wallrock alteration and vein calcite and barite in the epithermal veins. Geothermometry, based on chlorite compositions, indicates temperatures in the range 220-270 °C for chlorite formation (similar to the temperatures suggested for epithermal Au-Ag mineralization from fluid inclusions and oxygen isotopes.)

Conclusions There is little difference between the propylitized assemblages associated with porphyry copper mineralization and those associated with the epithermal. precious metal mineralization Both assemblages have a similar mineralogy and gross geochemical characteristics, and seern to have formed al similar P-T conditions (200-300°C - equivalent to epithermal hydrothermal conditions).

STATISTICAL ANALYSES OF A M INERALIZED STOCKWERK GEOM ETRY. APPLICATION TO TH E ROSIA POrEN I PORPRYRY COPP ER (ROMAN IA)

Ann e-Sylvie Andre\ Judith Sausse l, Mare Lespinassel, Sorin Udu basa1

, Luminita Gra neea 1

, Viori cn Milul and J acques L. u ray'

tR G2R. U.H.P. Nancy 1, B.P. 239. 54506 Vandoeuvre-Ies-Nancy Cedex. France Balcescu Av , sect. 1, 70111 Bucharest, Romania

1 Caransebes Str , Sector 1, 78 344 Bucharest-32, Romania

othermal mineral depasit fenn as result of focused flow of large volume of fluid and eability required for such rales of hydrothermal autflow must be related to high re density because non-fraclured rock has intrinsically low bulk permeability The lized stockwerk oflhe Rosia Poieni porphyry copper has bee" choose for a statistica!

hydraulic characterization of a type of hydrothermal mineral depasit in arder to .ter5tand how mineralized vein syslem evolves and grows A I D sampling on the mckwerk has been realized on 2000 fractures distribuIe d on five level of the open pir

10, 940, 1000, 1045 and 1060 m). Special anention was put on thickness. filling of each re and on space between veins.

tistical analyses !icalien of statistical analyses show that, in aII levels, the thickness distributien is fractal a fractal dimension D increasing from the deeper (910 m) to the highest level (1060 m)

showing a strong correlation with the copper grade. The spacing distributian are different ICCOrding to the difTerent levels : fraclal distributien for the 910m level and log-normal

'but ion for the others. The Cv values show clustering for ali the levels but evolutien of Cv with threshold thickness confirms the difTerence of spating distributien between the

-els. The Cv for the 910 m level decreases with the increase of the threshoJd thickness ~'Pical ofa fractal spacing distributien) whereas the other levels show constant Cv values

!fIelerogeneity in the characleristics (spacing and thickness) ofthe stockwerk can be shown at open pit scale where each profile has been considered as homogeneous. A precise study

reaJized on the 1000 m level shows that heterogeneity can equally be shown at the profile a e. Eight zones were distinguished on this profile (A to F) according to the density and the arure of the fiII ing. Statistical analyses applied in each zone show that the thickness

ribulion is always fractal and. as at the open pit scale, the fractal dimensions O differ in each zone and are linked to the copper grade. The majority efthe spacing distribution are log­.,rmal except in the more mineralized zones were il tends towards a fractal distribution The Cv values are variable in the zones even if its indicates a c1ustered organizat ion ofveins. Tbe more mineralized zones ofthe stockwerk seern to be characterized by thicker veins with • spatial organizatien as clusters. Vei" network with a fractal distribution of both thickness md spacing will be more prone to be mineralized because they form larger connected fracture Detworks allowing large scale fluid transport .

Ptrmeabilityestimation Permeability estimation has been realized takiog ioto aecouot aII the veins for a given profile Tbe mean permeability developed by aII the veins on each profile decreases from the deeper <vei (910 m) to the highest level (1060 m). High permeabilities developed on the 910 m

protiJe are linked to the presence of major drains and the clustered organizat ion of the veins 'Tbe level 1060 m. characterized by numerous and thin veins with a homogeneous spatial repartition. developed a pervasive permeability, diffused in the mass !Ns work IIas beell carr;ed 0111 \l'all rIIe framework of ,IIe Frel1c11 Metallogel1Y GdR program rtRarc/t. n,allks,o ,he ICR aud Ilie Ulli\'ersily of Bucharesi for their fech",cal SlIppOrfS.

HYDROTHERMAL O IALCOPY RITE-PY RlTE TRA~SFORMATION \VITA FORMATION OF PYRITE SP HERULITES

Radostina AtanaSSOv8, Iva n K. Donev Geologicallnstitute, BAS, 1113 Sofia, Bulgaria

Chalcopyrite from som. hydrothermal ore deposits like Rammelsberg (Germany), Temagammi (Canada), Darasun (Russia), Madan (Bulgaria) and others. sometimes includes peculiar spheroidal, atoll -like and other pyrite aggregates. DitTerent opinions about the mechanism of their formation are offered, e g. entrapment of earlieT pyrite assemblages., metasomatic crystallization (Vorobyov, 1974; Bonev, 1977), "vererzte 8aklerien" ar beginning oxidation (Ramdohr, 1980).

The detailed study of chalcopyrite-pyrite relationships in the lead-zinc vei" and metasomatic ore deposits of the Rhodope Mts. in Bulgaria (?vfadan district - Strashimir, Gradishte, Mogilata. Shumachevski 001 ; Luki district - Govedamik, Djurkovo; Madjarovo district) gives some new informat ion on their origin . The earl)' chalcopyrite in these deposits is represented by large and well·shaped crystals of scalenohedral. bisphenoidal and pseudorhombododecahedral habit . up to severa! cm in size

Several morpho!ogical types pyrite aggregates were obtained included in chalcopyrite: • Spheroidal formations with outer surface composed of small isometric cubic or

pentagondodecahedral pyrite crystals, and internal radial·co!umnar texture with radial pores and a central septaria-like hollow. Some spheroids directly contact with the host chalcopyrite but many others are detached by a concentric gap. of negative crystal shape The size ofthe spheroids is highly variable, in the range of 05 ta several mm.

• Spheroidal clusters of few large pyrite crystals also surrounded b)' concentric gaps; • Fine-grained porous pyrite mass occupying irregular parts or separate zones within a large

single chalcopyrite crystal; • Fine-grained pyrite crust covering some large chalcopyrite crystals and exactl)'

reproducing their outer crysta! faces. the internal chalcopyrite core being preserved. The morphology and location of the pyrite aggregates only in the chalcopyrite crystals

are strong evidence for their metasomatic origin Important procfs are also relics o chalcopyrite. presence of sphalerite stars of equal orientat ion in both phases. surface pseudomorphosen, etc. No regular crystalJographic orientat ion between pyrite and chalcopyrite exists. thus the replacement is elearly reconstructive, not topotaxic with a fuI! rebuilding ofthe host Slrueture

Some of the pyrite crystals in the gaps are partly overgrown by smal! crystals of late galena. sphalerite. arsenopyrite. and sometimes by fine pyrite whiskers, which is strong evidence for the hypogenic character ofthe process at relatively low temperatures

The replacement follows the reaction CuFeS2 ~ Cu + FeS2 in an open system, with removal of Cu and drastic volume reduction leading to great porosity of pyrite formations and panly to a later recrystallization ofits very fine grains

The slight deviat ion ITom the chalcopyrite stoichiometry (Fe Cu =1.013 > 1, according to Radulova, 1996) maybe is a factor for its panial chemical unstability. Chalcopyrite-pyrite transformation marks the specific changes in the environment during the hydrothermal ore­forming process.

References Bonev, 1. (1977). Metasomatic Spheroids and Porous aggregates of Pyrite in Chalcopyrite -

Geoc/rem., Mlller. alld Petrol (Sofia), 7, 35-46. Ramdohr, P (1975). Die Er:mineralien /Ind IlIre Venl'Gclls/lgell. Berlin, Akademie·Verlag.

3R

,..:W .... ~ A (1996) Chemical COmpOSltlOn of chalcopyrite from Madan ore district. -~"""hem., MII/eraI., Petrol. (Sofia), 31, 41-49

.. .:::-ooev., Y K (1974) Metasomatic spheriodal conglomerate of Pyrite in Chalcopyrite. -ew Data ojAfillerals USSR, 23, 50-57.

[l'CLUS ION ST UDY IN WOLFRAMITE FROM BAIA SPRIE US ING IR 1o.-, ..... nSCOPY

~_ ... Baillyl, Luminita G ra ncea\ Kalin Kouzma l1 ovJ

REM/MESY, BP 6009, 45 060 Orleans, France GlR 7566, niversite Henri Poincare, BP 239, 54 506 Vandoeuvre-Ies-Nancy. France

(·CNRS. IA rue de la Ferollerie, 45 071 Orleans cedex 2. France

11;;,t ..... """e is an uncommon mineral in epithermal deposits . A microthermometric study has perfonned an wolframite crystals rrom Baia Sprie using IR-microscopy, in order to

':;'nc:erlZe the physico-chemical characteristics of the involved hydrothermal fluids.

It;,_.p.oal contex t Sprie Ofe depasit belongs to the Baia Mare district located in the nonhwestern pan ' 1. It consisls OflWO mai" E-W veins. the Mai" Vein, ta the Nonh and the New (or

"eia to the South. Two main stages of ore deposition have been recognized The tirst characterized by a dominant pyrite-chalcopyrite assemblage associated with

a,<""d.mate amounts of hematite-scheelite-wolframite and magnetite The second

::::tion stage is dominated by pyrrhotite-sphalerite-chalcopyrite-galena-tetrahedrite­

e-freislebenite and gold.

~~:,:and methodology li te crystals samples appear within the early pyrite-chalcopyrite stage. filling late

as aggregates of idiomorphic crystals, up to 2 cm in length. I cm in height and 2 mm ess. associated with small siderite crystals. Doubly polished oriented crystal sections

_ .. ~50 jJm in thickness), cut II (010) were used in this study Transmission spectra of !duaJ wolframite crystals in the near IR region were collected using a Nicolet Magna-IR FTIR spectrometer (20 ~m apenure) at CRSCM-CNRS. Electron-probe microanalyses

) and X-ray element al mapping were performed. The microthermometric study was on a USGS - t)'pe microthermometric slage. mounted on an Olympus BHMS IR pe ()',;2 .5 ~m).

chemical composition of wolframite evolved from a Mn-rich core toward Fe-rich rims IR-rransparency of wolframite is strongly controlled by their Fe content as this

1IIi:a<JiIUI:ion controls the transparency in visible Iight primary and secondary fluid inclusions are observed. They correspond ta liquid-rich

phase incJusions at room temperature Whatever the fluid inclusion type. no phase . ion has been observed atler ice melting suggesting the lack of gazeous species such as

co" H2S, CH4, ). Primary fluid inclusions located in the core of wolframite crystals are Iy more saline (S to S.7 against 46 to 5. 1 wt % NaCI equiv, respectively) and exhibit

;hor Th (226 to 240 againSl 154 to 1 86' C, respectively) than those Iying along crySlals

39

rims. Secondary fluid incJusions are characlerized by salinities varying between 46 and 64 wt % Naei equiv for Th varying from 171 10 232°C.

Conclusions The salinity and Th ranges obtained an wolframite crystals are similar to those recorded by fluid inclusions in quartz and sphalerite from the same orebody

PETROLOGY AND K/Ar AGES OF VOLCANIC ROCKS FOR WIDEN BOR ZONE AS THE PART OF TUE TIMOK MAGMATIC COM PLEX (EAST SE RBIA)

Miodrag Banjesfvic' , Sasa Coei el, Marijana Radovic1

1 Geozavod.Gemini , Yugoslavia, 43 Karadjordjeva SIC, Belgrade 2 Institute for Copper Bor, Yugoslavia, Bar

Introduction The Timok magmatic complex (TMC) is the biggest volcanic area in East Serbia aod represents the consisting pari of the Apuseni-Banat-Timok-SrednogorieMagmatic aod Metallogenic Beii, one of the expressive structural units in the Carpath ian-Balkan orogen. The basement of the Timok magl1la lic complu is COllsisled of difTerent type of rocks, which were dated as Proterozoic 10 Lower Crelaceous. Above meutioned magmatic complex as well as Ihe basement a re composite part of Carp athian- Balkan lerrain (Karamata aRd Krstic, 1996). Recent research is based on petrological . voleanologica l, geochemical and radiometnc studies made in primary volcanic rocks SW from Bar (Brestovacka Banja area) and Bor mine zone, as the pan ofthe Timok magmatic complex. The samples have been analyzed on major and trace elements with rentgenofluorescent method (XRF - laboratory in Perugia and Moscow). Thiny analyses of the mineral chemical composition have been analyzed in Moscow. The same samples were optically investigated. Analyses of KlAr ages from separated minerals (homblende) and whole rock were dane in ATOMJU - Hungary. Volcanic depasits were studied over the facies concept usually used in vo lcanic area studies.

Results The studied primary volcanic rocks are divided as: al coherent volcanic rocks with lava flow and feeder dyke facies, bl aUloc1astic deposits with autobreccia and hyaloc1astite facies and ci pyroc1astic rocks with pyroclastic now and pyroclastic fa li deposit. Resedimented syn­eruptive and volcanogenic sedimentary deposits were not the subjects of detail study_ The SiO, content in these rocks varies from 51 ,47% to 60,48%. Due to MgO :FeO(t) .Na,O+K,O ratio, the calc-alkaline tendency of magmatic ditTerentiation is confirmed in aII samples. On the Si02:Na20 +K20 diagram for classification of voleanic rocks, analyzed rocks correspond from basalt ta andesite. On the 1\lbN:Zrrri02 diagram are gathered in the basaltic andesite field. New data for radiometnc K-Ar ages were received: I Bar mine zone - 89,7 ± 3.6 Ma (monominerali c fractians-homblende separated from homblende andesite lava now). 2 Zone SW from Bor (Brestovacka Banja areal - 76,7 ± 3,0 Ma (whole rock of pyroxene basaltie andesite feeder dyke)

Conclusions The elucidated calc-alkaline character, litological charactenstics typical for stratovolcani complexes as well as macro and trace elements content and ratio as shown in the

It-=-, • .,on diagrams, indicates subductive affinity of magmas. From radiometric data it is Timok magmatic complex magmatism is of Turonian to Maastrichtian age

_ ' ) SO, funher investigations should provide more precise data about the age of dlmnal fluids and mineralisation.

I':;:<~es : II S. and Krstic, B. (1996): Terranes of Serbia and neighbouring areas. Terranes of

Serbia, Brezovica. 25-40.

OF BANATITES: FROM ONE GEODYNAMIC PARADIGM TO

Rerza l

'1I':..aOgi"cal Institute of Romania, Caransebes str. No 1, Bucharest, Romania, RO-78344, .r

Cona (1864) coined the term "Banatites" for Late Cretaceous intrusions and volcanics Banat (new SW Romania) and Serbia. Similar and coeval rocks were described under collective name in the Apuseni Mountains and olher areas in W Romania. In

I-::::sorie, Bulgaria, Late Cretaceous magmatic rocks are a1so well represemed and " even if Bulgarian aUlhors never used the term "Banatites" to describe them.

ant ore deposits (Cu, Mo, but also Fe, Au, Pb, Zn, W) are mostly associateq with acid ~_Ilti',c intrusions in aII the above areas along a belt 1500 km Iong and up to 70 km \Vide,

_'ve an economic incentive to the petrological studies More than for any ofthe Alpine I __ -'tic provinces in SE Europe, rhe origin of the Banatitic magmas \Vas argued using the

nl geodynamic rheory ofthe day.

geosync1inal paradigm was implicitly or explicilly used by ali geologisls in the first half . ohe 201h century and first applied 10 Banatites by Stille (1953). Late Cretaceous tO

ne volcanites and intrusions were labelled as "subsequent" (Giuşcă el al" 1965, 1966) -precocious subsecvent" (Ghitulescu el al., 1965) ta invers ion of the Alpine geosyncline,

ifreferences to tectonic phases ("Sub-Hercynian volcanism", "Laramian magmatism") syn-orogenic connotations,

plate tectonic paradigm was eXlensively used in the last decades ta model the oTigin of ilaDatites as subduction-relaled, bUl \Vas difTeremly used in each country. In Romania. the

el of Râduleseu and Sănduleseu (1973), stil! popular and refined by Sânduleseu (1984), !bsso- Sănduleseu e. al. (1984), Vlad (1997) and Sânduleseu and Visarion (2000), postulales

westward-directed Late Crelaceous subduclion lones involving the Transylvanian (Main i"Clhys) and Severin (paralJel. intra-European margin) paleooceans, In Serbia, eastward­=ed subdue.ion of.he Vardar (Te.hys) ocean was claimed by Jankovic (1977, 1997) as

_ erau'ng Hanatllic ma:grrr<ff, l'tr BU'L'g-cn"is. lJ,xCt1,'Ie.'.',i el ,il). (J9.7~) .nr.DpD.Sed that caJc-alkaline gmatism of Srednogorie was due to nonhward-directed undenhrusting of the Vardar

..oospheric slab which "(afler the collision of the sialic plaIes), continues, detached, jescending imo the upper mantIe". Both the dominant calc-alkaline geochemical trend ofthe _ eous rocks and the metallogenetic features of the associated ore deposits were extensively ~ to suppon these regional subduction models. However, the change in subduction 5rection al the South Transylvanian Fault system, noticed by Burchtiel (1980), 'wilh Ihe

~icolescu S, Cornell DH, Bojar A-V (1999) Age and tectonic sening of Bocsa and Ocna de Fier-Dognecea granodiorites (soulhwesl Romania) and of associaled skarn mineralisation. Mineralium Deposita 34, 743-753

Popov P (1981) Magmatectonic features ofthe Banat-Srednogorie Belt. Geol Balcanic., 11(2), 43-72.

Popov P (1987) Tectonics ofthe Banat-Srednogorie Rift: Tectonophysics 143,209-216 Popov P, Berza T, Grubic A (2000) Upper Cretaceous Apuseni-Banat-Timok-Srednogorie

(ABTS) magmatic and metallogenetic Belt in the Carpathian-Balkan Orogen. ABCD­GEODE 2000 Workshop, BorovelS, Bulgaria, Abstract Volume,69-70.

Rădulescu DP, Săndulescu M (1973) The plate tectonics concept and the geological structure of the Carpathians. Tectonophysics 16, 155-161

Russo·Săndulescu D, Vâjdea E, Tănăsescu A (1984) Neocretaceous.Palaeogene subduction igneous rocks in the Romanian Carpathians - mutual relationships, succession and areal distribution DS InSI Geol Geof, 64,111-119

Săndulescu M (1984) Geotectonica Romaniei Editura Tehnica, BucureSli, 336 pp. Săndulescu M, Visarion M (2000) Crustal structure and evolutien ofthe Carpathian-Westem

Black Sea areas. FirSl break, 18 3, 103-108 Stille H (/953) Der geotektonische lVerdegang der Karpaten Geologie Beih, VIU. 239 pp,

Hannover. Vlad Ş (1997) Caleie skams and transversal zoning in Ihe Banat moumains, Romania" indicators

efan Andean-type setting l\1ineralium Deposita 32, 446-471 Willingshofer E (2000) Extensian in colfisional orogenic belts the Lale Cretaceous evo/utian

of the Alps and Carpathians PhD thesis, fetherlands Research School of Sedimenlary Geology, 146pp

MAGMATlC·EPITHERMAL TRANSITIONS IN TElE LOZEN PB·ZN DEPOSIT, EASTERN RHODOPE , B LGARIA

Kamen Bogdanov', YOIZO Yanev 2

I Sofia University, Faculty ofGeology and Geography, 1000 Sofia, Bulgaria 2Geologicallnstitute. Bulgarian Academy of Sciences. 1) J3 Sofia. Bulgaria

The Paleogene volcano Lozen is situated in the NE margin of the Eastem Rhodopean Vo\canic Area (ERVA) Small diorite intrusion in addition 10 three Ca-alcaline volcanic phases of Upper Eocene age (K·Ar age: 36-35,5 Ma) hoSl the epithermal Pb·Zn·Ag lenses and veins ofthe Lozen deposit The first vo\canic phase is represented by complex of rhyolite domes and associated p)'roclastic rocks, surrounded by calderon ring of sub-volcanic rhyo­dacites and dacites of the second phase. The third volcanic phase is represented by \arge rhyolite dyke According [Q the two-feldspar thermometer the temperature of formation ofthe first two phases of volcanic rocks is at the range 740-710 °C and PlI20 1,5 kbar as estimated by amphibole geobarometer Feature typical for the volcanic rocks is their lew Rb (160-180ppm) as well as the high Sr and Ba (1700 ppm) content and the presence of small Eu anomaly. The porphyry phases ofthe volcanic rocks consist ofbiatite and amphibole ,quanz, sanidine, plagioclase. Ihe latler three containing also melt inclusions.

The main ore bodies are hosted by Teniary conglomerates, rhyolites and associated pyroclastic rocks and occur as ga lena-sphalerite-chalcopyrite lenses, sheet-Iike bodies and veins in the shallow levels Chalcopyrite dominated porphyry type veinlets and disseminations are common1y observed in the deeper levels, close to the subvolcanic diorite

OEM: Two digit al elevation models: one oceanic (2' arc) and ooe continental (30" arc) with a 'U\lctural analysis oflhe lopography

lAGERY: SPOT 4 VEGETATION® images at Ix l km

GEOLOGIC MAP COVERAGE: Present state of geological coverage

GEOLOGIC SYNTBESIS: Synthetic geological map at 1' 1,500,000 scale and simplifi ed -nap wlth morpho-structural domains and main tectonic elements \ 'OLCANIC: Data on Holocene vo1can\sm G EOTBERMAL RESOURCES: Based on inventories at present being compiled for the

U GEOCEIEMISTRY: Composition and age of magmalic and volcanic rocks - isotope data O RE DEPOSITS: Linked to a database under Access®, using a new metallogenic lexicon md iocluding mineralogical, flui d-inclusion aod isolopic data of the main deposits G EOCHRONOLOGY: Synthesis of existing data, methods used, reliabili ty, references, etc. fcollaboration with Utrecht University) ~tlNING DlSTRlCTS: Delimitation, magmatic and structural controls, potential, etc. BEAT FLOW GRA VIM ETRlC: Bouguer anomaly calculation; isostat ic correction and corresponding residual anomalies, vertical gradient .

EISMIC: Distribution of eanhquakes in order to bener constrain crustal structures \IOBO: Depth contour map

TOMOGRAPHY: 30 model of the lithospheric slructure (collaboration with Utrecht Univtrsity)

OCIAL ANO ENVTRONMENTAL FACTORS

Rt ferences: ( assard, D , 1999 GlS Andes on the WEB' hnp,//www brgm frlsigand

TRE LATE CRETACEOUS CBELOPECH Au-Cu HIGH SULFlDATlON DEPOSIT, REDNEGORIE ZONE, BULGARIA: REGIONAL AND LOCAL GEOLOGICAL ETTING, AND GENETIC AMBIGUITlES.

1. Chambefort \ R. Moritz\ R. Pe.runo"l aod A. ArizanoyJ 1 Sectian des Sciences de la Terre, Universi ty of Geneva, Switzerland. l Geological lnstilute. Bulgarian Academy ofSciences, Sofia, Bulgaria. , BIMAK AD, Chelopech mine, Sofi a District, Bulgaria .

Aims of this study are to identify the geometrical relationship among the host rock types. the structures, the alterat ion pattern nnd the orebodies in the high· sulfidafidri Au-Cu Chelopech deposit, and to establish the relationship between magmatism and mineralization. Recent research on this deposit , located in the Panagyuriste ore region,

rednegorie tectonic zone, Bulgaria, demonstrates that the geometry of the hydrolhermal system is tightly linked to difTerent breccia I)'pes. Furthermore, the ore bodies are structurally controlled, this tend to suppose Ihat the initial setting of Chelopech has been tilted and oYerprinted by a younger deformation event.

The Chelopech mine is one of the largest European gold deposits, and is located within the nonhem pan of the Panagyurishte ore region in the Srednegorie metallogenic belt, Bulgaria. The Chelopech deposit is hosled by an Upper Cretaceous volcanic and volcano-sedimentary complex, transgressively overlaying Precambrian and Paleozoic basement rocks (Popov et aL, 2000). Magmatic rocks associated with the ore deposit have a calc-alcaline to high-K calc-alcaline composition, and are essentially composed of homblende and plagioclase (An 40) daCÎte and trachyandesite. The Chelopech deposit contains enargite, tennantite. goldfieldite and alunite typical of precious metal high-sulfidation epithermal deposits, but also includes an early stage of banded massive pyrite ore that is typically described in volcanic massive sulfide (VMS) deposits. Three different models have been proposed: (a) a classical VMS origin; (b) an epithermal high-sulfidation origin and (c) overpnnting hydrothermal events with early VlvtS formation in a marine setting, followed by uplift and formation of a high-sulfidation enargite-precious metal deposit in an aerial setting. However, recent observations in the westem pan ofthe deposit show Ihat Ihe banded massive pyrite is a fine tuff essentially composed of dickite and pyrite, typical of intense argillic alteration in epithermal systems. Moreover, the texture of this rock can be more irregular, and not necessarily well banded as described previously.

Ore bodies and the majority of the rock units have a NE-SW direction with a SE dip. Fault planes with essentially a N40-50E direction delimit the ditTerent lithological units and separate the westem block from the eastern block in the mine. The ancient host volcanic system presents a discordant limit al ilS top with a synclinal filled with sedimentary rocks. The deposit is panly overprinted by a younger (alpi ne?) tectonic event. The different sedimentary rock complexes in the immediate vicinity and the volcanic host rocks display puzzling geometrical, tectonic relationships that remain ta be resolved.

Most of ore bodies are hosted by breccias including phrealomagmatic and magmalic hydrothermal breccias, according 10 Ihe terminology of SiJlitae (1985). These breccias represent the majority ofthe \VaII rocks like in many high-sulfidation epithermal systems (e.g. Rodalquilar, Spain. Arribas el al, 1995). In underground exposures, massive magmatic rocks and tuffs represent the remainder of the hast rocks before extensive fracturation. Breccias generally contain altered massive andesite fragments surraunded by a flour matrix, with abundant ore veins The breccias v.ere major channelways for fluid circulation. as in many valcanic-hasted epithermal systems (e g Carben and Leach, 1998).

The dickite- and pyrite-dominant composition of the zones with banded massive sulfide in the westem pan ofthe deposit is untypical for a VMS depasit . A more likely interpretation is that they result from the replacement of cenain host rocks in the epithermal environment by interaction with very acid fluids associated to the contemporaneous calc-alcaline magmatism. The orientat ion ofthe ore bodies and the host rock structures show Ihal the Chelopech depasit has been tilted after deposition, and o\'erprinted by faults during the Late Cretaceous possibly related ta Alpine lectonics. before deposition of the sedimentary CQver formations. Breccias represent the major component of the immediate host racks of the ore bodies. An understanding of the relationship bet\\een them and the other wallrocks is fundamental for unveiling Ihe formation ofthe high-sulfidation Chelopech deposit.

References Arribas et al (1995) Econ Geol , 90,795-822. Carben, G.J and Leach, T M (1998) Econ Geal , Special publicatian 6 Papav, P et a1 .(2000) Elatsite-Chelapech ore field . In S Strashimirav

and P.Popov (eds) Field guidebook, ABCD-GEODE 2000 \\orkshop, 8- 18 Sillitoe, R. ( 1985). Econ Geol , 80, 1467-1514

ORE DEPOSITS OF THE VORTA- DEALUL MARE AREA, SOUTH APUSENI 'HS_, ROMANIA: TEXTURES AND A REVISED GENETIC MODEL

Cristiana L. Ciobanu l, Nigel J. Cook l aud Paul M. Ivaşc3nu 2

' Geologica l Survey of Norway, N-749 1 Trondheim, Norway ~ Geological Institute of Romania, Bucharest, Romania

Zn-Pb-(Cu) mineralisation al Vorta nod Dealul Mare in Ihe a lkali basalt-hosted Vorta­Dealul Mare-8arbura belt. S. Apuseni 1\115. is examined. Primary syngenetic VHMS genes is is favoured , overprinted by hydrothermal aud tectonic reworking.

Vorţa is the largesl of severa l massive and disseminated Zn-Pb-(Cu)-(Ag) deposits in the Middle to Late Jurassic ophiolite-hosted E-W trending VOrţa-Dealul Mare-Barbura belt (VOMB), Bărăşti Formation (Ciobanu & Gheuca 1997), Căpâlnaş-Techereu Nappe, S. Apuseni Mts (SAM) The deposit Îs a discontinuous E-W alignment of lenses with varia bie grade (ca. 2.5 Mt @ 1 8% Zn+Pb). Dealul Mare, 6 km E of Vorţa. is smaller but richer (est. 0. 5 MI @ 3% Zn, 1 9 % Pb) Two mineralisation styles are seen at V0rta. Compact massive ores occur as lenticular and spheroidal bodies with sharp contacts ta wallrock. Characteristic are mineralised boulders Iying along the mineralised horizons (mugle). showing marked concent ri c zonation, enveloped by fine-grained ore The orefield also contains a halo of veinlets and di sseminations, which overprint massive mineralisalion. All ores are strongly tectonised ; eli eelle/oll and pinch and swell structures are characleristic at Vorţa. AI Dealul ~1are, a dominant polymetallic mineralisalion appears as massive pockets of ore in two elongale. N\V-SE-striking zones (5 and 10 m wide, 50 and 300 m long). Extensive reworking, wilh remobili sation around the pockets, and pyrite dissemination in wallrock, parallels ores at Vorţa . The pockets are encJosed. together with rragments of wallrock. in a vuggy, quanz-rich breccia malrix. Host rocks are alkali basalt lavas with a 'mandelstone' character, altered to an assemblage of calcite-quartz-chlori te-albite. Fresh alkali basalts are vesicular and rich in cm­sized analcime. pyroxene and plagioc1ase, g iving them an agglomerate-like appearance. Alteralion completely replaced ana lcime and other zeoli tes.

In both deposits, characteristic primary features typical of VHMS are seen, ineluding fra mboids, atolls, accretionary, collomorph and olher bacteriogenic and elastic structures, tine-scale banding and diagenetic textures. However, both ores also display deformat ion teXlures indicative ofreworking, by hydrothermal act ion, tectonic brecciat ion. micro-shearing and micro-scale ore remobi li sation. Tectonic defonnation is most marked at Vo.,a, whereas brecciation and a fluid-rich 'hydrothermal' overprint , relating 10 nearby stocks aod dike swarms, is most evident at Dealul Mare. These are ioterpreted as Eocretaceous inlrusions, widespread in SAM ophiolites. However, Neogene magmatiles. known rrom Barbura. but not yet proven at Dealul Mare, may play a rele in further modificat ion of the ore; geochemical mapping suggests three distinct au reoles (Caraveleanu el al . unpubl . rep. Prospectiuni 1992)

We favour syngenetic submarine-seafloor syngenetic stratiform ore formation al seamounts within alkali basalts across the VDMB beii . We thus refute olher models presented for the deposits (Savu & Nicolae 1975; Cioflica et al. 1984), agreeing thattextural evidence for a syngenetic volcanogenic 'Kuroko-type' genesis (Udubaşa et al. unpubl. rep IGG 1978) is indeed convincing. We disagree, however, with the Kuroko ana logy since ores are

intimately associated with alkali basalts, rather than the dacites Erosion of the alkali ba salt seamounts \Vas followed by intra-oceanic subduction. consistent with models for the Oxfordian SIV Te'hys, which show SAM along 'he margin of 'he subducting Melia,a Ocean. The Vardar Ocean \Vas contemporaneously spreading as a back-arc basin (Stampfli el al. 1998)

References Ciobanu, C & Gheuca, 1. (1997) Rom. 1. Mineral. 78, suppl 1: 10-12 Cioflica, G et al (1 984) Analele Univ. Bucuresti, ser. GeeI 33 2-23 Savu, H & Nicolae, 1 (1975) D. S. lnst. GeeI. Geofiz. 61 179-196. Stampfli, G M. e' al (1998) Bull. GeeI. Soc. Greece3211 113-120.

TELLURIDES FROM THE LARGA HYOROTfIERMAL SYSTEM, SOUTA APUSENI MTS" ROMANIA, ANO TAEIR GENETIC SIGNIFICANCE

Nigel J. Cookl, Cristiana L. Ciobanu l and Reidar Boe2

I Geological Survey of orway, N-7491 Trondheim, orway 2 SINTEF Petroleum Research, N-7465 Trondheim, Norway

Bi- and Ag-tellurides are described from deep levels of Ihe Larga-Fata Băii field, suggestive of a hydrothermal system strongly zoned with respect ta jSl and temperature.

Miocene epithermal Au-deposits in the S. Apuseni Mts feature an unparalleled abundance of telluride minera ls Au- and Au-Ag tellurides. typical of higher levels, are bener documented (e.g. at Săcărimb, Stănija) . The occurrence and significance of other tellurides, in these and other deposits remains, however, not well understood, especially at deeper levels, even though 'hey have been sporadically repol1ed (e g. a1eksi,e and pilsenite at SAcărimb).

Larga, with Fata BAii. Haneş, Breaza & Trimpoiele, constitutes an orefield al lhe SE end of the Zlatna-Stanija volcanic zone. Larga (+761 m) is unique for the area in that early 201h

cemury exploitation concentrated on 3 lenses of high-grade gold-pyrite ore at the contact of Paleogene Fata Băii conglomerate and Badenian shale. Dense, NW-SE striking, <500 m long veins ofthe Faţa BAii group occur in conglomerate at similar leve1s, 500 m 10 l\TW. Here, Au­tellurides are abundant , the type locality for native-Te and tellurite, TeO]. Unlike Breaza or Haneş, no relationship to large andesite bodies or volcano roots is seen at Larga and Fata Băii . We investigated mineralisation in an area of ca I km1

, accessible rrom the Horea exploralion gallery (+51 6 m), 250 m below exploi'ed ores a' Larga and Fala BAii We distinguish: (1) a NW-SE, interrupted strike of veins across 800m, hosted in Fata Băii conglomerate. At Ihe NW end (Cloşca gallery), direc,ly underlying Fala BAii , veins are Au-rich, Py-domina,ed, c1ustering around small andesitic intrusions and include a SO m diameter Cu-stockwork. At the SE end, Vein 625 (O' Vest gallery) is the longest (200 m) ofseveral steeply dipping veins and lies direc,ly benea'h the pyri,e lenses The shared assemblage is arsenopyri,e (Asp), pyrite (Py), galena (Gn), sphalerite (Sp), chalcopyrite (Cp), marcasi,e (Mar), IOllingi,e (La) and Au within brecciated carbonate-quartz-c1ay mineral-chlorite gangue. An As-rich character dominates in veins beneath Larga~ Au occurs chiefly al grain boundaries in Asp-l,O (2) a parallel strike of Zn-Pb carbon .. e replacemen' and skarn, seme 400 m 'o NE, relating 10

a limestone marker horizon in the conglomerate: A lenticular body, 500x150 m (0° Est

_ ery) of mineralised boulders and geodes wilhin altered conglomerate and secondl y, prnet-epidote skam (Padina gallery). 500 m further NW, along skarn st rike, porphyry Cu-Au l1Înerali salion is intersected in drillcore al the margin ofthe Trîmpoiele andesite. i.inking aII these mineralisation styles is the presence of Bi- and Ag-tellurideslsulpho-

lurides: tet radymite, Bi2Te2S, wilh Pb- and Se-bearing varieties (Ttd), Tsumoile, BiTe, :dlurobismut ite, Bi,Te, (Tbs) and rucklidgeite solid solution, (Bi,Pb),Te. (Ruc). Ag-minerals .ue hessite, Ag2Te (Hs) and cervelleite, Ag..TeS. lhe laner containing several wt.% TI. In leÎns, the Ttd+Ruc+Hs+Gn assemblage, associaled with Au, is most typical as inclusions in ţsp . In skarn ore, tellurides occur al Sp- and Py-gangue borders. Assemblages are Tbs+ Ttd ar Tbs+Ruc, with Gn inclusions abundant in Tbs. Apart from Bi- and Ag-minerals, there is llso abundant evidence for initial 'iss', from which Cp and Po exsolved. Pa is largely rep laced . Py and/or Mar. This is the tirst reported Romanian occurrence of rucklidgeite and

.:ervelleite. !be Te-rich character of the syslem c1early persists al deplh, yet Au-tellurides are not seen. ~sins Afifi et al. (1 988), this is interpreted to reflect much-reducedjTe, at depth. At +516 m, lfe2 is below the stability limil for calaverite or altaite, yet still wilhin the stability field for !dIuIobismutite and hessite. Larga-Fata Băii can be viewed as a strongly zoned system with ':"eSpect tOfie2, and also ta temperature, which may have exceeded 400-450 ec al deplh.

References >.fifi , A.M. et al. (1 988) Econ. Geol. 83 : 377-394 and 395-404.

1HE MASS SPECTROMETRlC METAOD FOR ANALYSIS OF VOLATILE SPECIES FROM FLUm lNCLUSIONS

Sub Cuna\ N. Palibroda l, C. Cuna\ 1. Pintea2

National Institute of Research-Development for Isotopic and Molecular Technology,Cluj­_ ' apoca : Geologicall nstitute of Romania, Bucharest

Fluid inclusion studies aid the earth scientist in his understanding of a wide variety of ,geological processes both an the eanh and in the solar system. The concentrat ion of the compounds present in fluid incJusion may be present at trace levels. We present a method for qualitative and quantitative analysis of gases released from geological sample.

Tbe method of fluid reJease is by crushing a known amount of sample (200-300 mg) with a special device. This device was connected directly via a four-way switching valve te the gas chromatograph coupled with a double focusing mass spectrometer. The crusher was constructed from stainless steel and has a pisten and cylinder. The silicon rubber o-rings were :Jsed ta seal the crusher. There are two stainless-steel tubes in the lower part ofthe crusher for the H2 carrier gas and the two upper tubes to permit operation of the crusher under a H2

aunosphere. The sample was crushed by pressing the piston. Ali samples were crushed at mam temperature.

The analysis of the constituents in fluid inclusions was performed by GC-MS. The ,echnique used was to select a specific mass (mle=!4 for CO" mle~ IS for CH.., mle~34 for HJS and mle=64 for S02) and run a chromatogram by monitoring that one mass (often called mass fragmentegram). The sensitivity ofthis method is up to ppb.

We have prepared the standards for the calibrat ion and we ha\'e measured the CO2• O2, CI-L and HlS from some minerals and rocks The amount "x" of gas released from fluid inclusions was caJculated with relations:

X - .b.. - _I_~lg - - s M, M, / $ '$

were: g. is the amount (in ~g) of gas released from sample M, is the weight (in grams) of the sample gs is the amount (in ~g) of the gas standard used 1. and Is are the width (in mm) al 50010 height ofthe sample respective standard peak.

Several examples oftypical analytical results from same samples are presented in the below table No. Sample ~gCO';g sample ~gCH.lg sample ~gSO';g sample ~gH,S/g

amount[g] sample 1. 0.483 2.24 0.033 <SxIO < 10 2. 0.266 2.83 0.053 <SxIO~ <10 3. 0.202 0.816 0.08 <SxlO <10 4. 0.222 0.96 0.039 <SxIO 1.6xl0 ConchlSlons. We have bulit a crushmg devlce for Telease the gases from fluid mcluslons and have analysed these gases by GC-MS. The method is very sensitive and allow5 the measurement ofthe gases al nanograme levels

Rererences 1. Andraws F., Holzer G., Roedder E., Gibson E.K., Ora J , J. of Chromat, 302, 181-193,

(1984) 2. Andraws F , Gibson E.K., American Min , voi 64, 453-463 , (1979) 3. Andraws F , Gibson E.K Jr, Anal Chem , 50, 1146-1151 (1978) 4. Barker C., Torkelson B.E , Geochim. Cosmochim. Acta, 39, 212-218, (1975).

ISOTOPE RA TlO MASS SPECTROMETRY APPLlED IN GEOLOGY

Stela Cunal, C. Cunal

I National Institute of Research and Development for lsotopic and Molecular Technology. Cluj-Napoca

Many of the processes in nature express a preference of ooe isatope over another. As a results of these natura] phenomena the isotope ratia ma)' vary and will lead to an isotope effect. We can measure these isotope effects by the use an isotope ratio mass spectrometer (IRMS). Absolute abundances of isolope are difficult 10 quantify with accuracy and these are expressed as the difference of absolute isotopic ratios relative 10 the isotopic ratio of an arbitrarily defined standard. The standard reporting natatian for most stable isotopes is Ihe delta notation, which is defined as follows:

R - R O pk = .-,.. ~laDdo.rrI xl 000 - R Jlalldlrl

The resulting values are expressed in parts per thousand or more commonly "per mii" We present the methods developed in our laboratory regarding slable isotopes of carbon, oxygen, sulfur and hydragen.

50

Carbon. The gas used in IJc /De measurements is CO 2 The methods which we have used for preparation of C02 \Vas - carbonates are reacted v.ith 100% phosforic acid al temperatures 2SoC - organic compounds are oxidized al - lOOO°C by oxidizing agent CuO The precision ofthe analysis with our mass spectrometer ATLAS 86 Îs ± 0,1%0. We applied the carbon (and axygen) isotopic compositions of limestone ta understand palea­environments and as signatures of provenance for cJassicaJ marble. Oxygen: C02 is the gas used in mass spectrometric measurements. Different methods we have used ta liberale the oxygen from various compounds ' -carbonates are reaeled with 100% phosforic acid al the temperatures between 25"C and ISO°C depending on the carbonate - the 180 / 160 ratio in water is usually determined by equilibration of a small amoun! of C02 with a surplus ofwater. The precision ofthe analysis is ± 0.2%0. Bydrogen: The determinat ion of the DIH ralios we have performed on Hl gas. \Vater is converted to hydrogen by passage over hot uranium at about 750°C. We have measured the DIH ralios wi lh a mass spectrometer SMAD I built in our institute. We applied the hydrogen and oxygen isotopic compositions ta environmen!al studies and geochemical evolution processes. Sulfur: The gas used in mass-spectrometric measurement is 502• Pure sulfides are converted in vacuum to SOl by reaction with CuO al 1000°C. The method for preparat ion of S02 rrom sulfate minerals is by combust ion in vacuum with CU20 al 1150°C. Ta prepare S02 from dissolved H2S we coJlected Ag2S by nitrogen-stipping in AgN03. AglS is combusted in vacuum with V20 j at 1000°C. \Ve have studied the variability of 034S in hydrogen sulfide dissolved in waler. The precision ofthe analysis is ± 0,3%0.

Referenceş 1. Platzner IT., Habfast K . \Valder A.l.. Gaetz A , Modern lsotope Ratia Mass

Spectrametry, Ed. l.0. Winefarder, Jahn Wiley & Sans, New York, 1997 2. Cale C.V., Crassley O .. A.Jr . Carbon lsatope Techniques, Ed. David C. Caleman and

Brian Fry Academic Press. New York, 199 1.

UPPER CRETACEOUSffERTIARY MAGMATlSM, METALLOGENY ANO GEOOYNAMICS OF THE SERBIAN PART OF THE BALKAN PENINSULA

Vladica Cvetkovic l, Dejan Prelevic\ Stevan Karamata l,

'Facuhy afMining and Geolagy. Ojusina 7, 11 000 Belgrade 2Serbian Academy ofSciences and Ans, Knez-Mihailova 35, 11000 Belgrade

The contribution presents the Upper Cretaceous!Tertiary geodynamics of the central Balkan Peninsula inferred from magmatism and metallogeny. Five diffe~nt igneous formations with specific metaUogenetic features ha\'e been recognized. They resulted in a succession of con\'ergen~ soft-collisional, post-coUisionaVrel:u.ational and extensional processes.

The final terrane organizati an in the central Balkan Peninsula started in the UC by c10sure of the last oceanic realm of the Vardar Tethys. From the Upper Cretaceous convergence, thraugh the Oligacene collapse of the Dinaride orogen ta the Neogene extensian tectonics in the Pannanian basin, five difTerent igneous farmatians de\'eloped.

;1

(1) Upper Cretaceous!Paleogene 5ubduction related calc-alkaline formation of East S~rbia, which Decurs in I\VO sub-parallel zones of the Ridanj-Krepoljin Selt in the west aod Tlmok Magmatic Complex in the east Facial characteristics (stratovolcanic complexes), petrography (andesire dominated) and albeit scarce geochemical data (e 8. high LLLElHFSE) indicate volcanic arc aod ensialic back-arc setting, respectively. The melsllogeny ofthis formation is dominated by Cu, Au/±Mo, Zn, Pb, locaIly Pd. (2) Paleogene mafic alkaline formation ofEasr Serbia, which developed atler Ihe terminatie" of Ihe subduction along the precedent fore-arc and arc. The magmatism characterize undersaturated oear primitive asrhenospheric ma~mas «43% 5i02• high FTSE. low LILElHFSE, fractionated REE, free of Eu-anomaly, ' Srl"Sr- .703), which originated aRer a slab-breakoff (Jovanovic et al., 2000) (3) Late PaleogeneJNeogene plutonicJvolcanic formation of which two compositionally different suits may be distinguished: (a) calc-alkaline (CA) and (b) potassiclultrapotassic (p1UP). The CA suit is represented by various granitoid bodies (predominantly l-type calc-alkaline, 87Srt"Sr-.708) and silicic composite volcanoes ofien with calderas. more rarely stratovolcanoes (MKJHK calc-alkaline acidlintennediate rocks displaying high LILElHFSE, fractionated REE with a ubiquitous Eu-anomaly and "Srf6Sr- .708- 709). The PIUP suit comprises small bodies, dykes, rare lava flo\\'s characterized by exotic petrography. e,g. lamproites, lamprophyres or kamafugites (?) displaying very high LlLE/HFSE, TNT troughs, extremely fractionated REE with a distinctive Eu-anomaly and wide range ofisotope ratios (81Srf6Sr=.705-.720), Generally, this formation is characterized by Pb-Zn-Ag-Sb/±Cu-W-Moi metallogeny and it onginated during the Oligocene post-collisional collapse ofthe Dinaride orogen (4) The Neogene granitoid formation ofthe southem margin ofthe Pannonian basin, which is spatially associated with the older graoitoid formation S-type peraluminuous granites prevail aloog with rare I-type calc-alkaline granodiorites. The rocks of this formation feature higher strontium iSOlope ratios ("Srl"Sr -. 709->.720) and U-Sn-Nb-Ta-REE-Be metallogeny. (5) Badenian volcanic formation of Nonhem Backa, represented by deeply buried thick (at some places more than 400 m) rhyodacitelrhyolite primary pyroc1astics, rarely lava flows and related autoclastic deposits. This magmatism may have its counterparts in eogene S-type granitoids ofthe southem margin ofthe Pannonian basin as well as in Middle Miocene tufTs in Hungary. Both (4) and (5) formation are re lated to the extension in the Pannonian basin.

References Jovanovic, M., Downes, H., Vaselli , O., Cvetkovic, V, Prelevic, D & Pecskay, Z. (2000):

Petrology and Geochemistry of Palaeogene Mafic Alkaline Volcanic Rocks of East Serbia. Vijesti 37/3, Sp. Issue PANCARDI2oo0, Abstracts, p 56

G ENETICALLY MODEL OF TH E AYDROTA ERJl1 AL i\1 rN ERALlZATIONS ASSOCIATED TO NEOG ENE MAGMA TISM FROM TIl E BAIA MARE AREA

Gh. Oamian l, F. Damian1

The onh University of Baia Mare, 4800 Baia Mare, V Babes Street 6'JJA, Romania

The Baia Mare and Oas district reprezents the V pan of the eogene volcanic chain inside the East carpathian Mountains. The volcanism is related to the subduction processes of the orogenic Carpathian chain. The subassment was deeply dislocate by the E-W fractures pre-Neogene which controled the volcanism and metallogenessis development. The volcanic acti\'ity began with the explosive acid phase Lower-Badenian-Sarmatian age,

5)

Madan ore field Îs developed in the southwestem flank of Ihe Central Rhodope Da me and inc/udes 40 deposits and numerous ore occurrences. Ore mineralisation is mainJy of vein rype and Jess merasomatic replacemen! ore bodies ar crosscurs of veins wirh marble horÎzons. h is coe of rhe mOSI significanr manifesrations of vein type Pb-Zn eres in the worJd - Qver 7 MI metal Pb and Zn, both mined and in reserves. A verage conleor of Ag in eres is 28 - 30 ppm and much higher in galena concentrate and studies about the farm of presence of Ag in Dfes is quite important.

Recently repor1ed silver phases and silver-bearing minerals are as followed : Ag­tetrahedrite and Ag-tennantite, freibergite, binnite. native silver, miargyrite. matildite, acanthite, polybasite, pyrargyrite, freieslebenite, electrum and polyargirite? (Kolkovski and Manev. 1988; Kolkovski et aL , 1996). Through optical and microprobe determinations most of mentioned above minerals are proved in main mineral paragenetic associations - as in the quanz-galena-sphalerite (productive one) and later formed carbonate and arsenopyrite­suphosaJt. The most common silver-bearing phase is Ag-Zn-tetrahedrite and in some cases it represents typical freibergite with AS content up to 30 wt . %. During the recent study new silver-bearing phases as pearceite (Ag1.l UCuJ81Zno_o.EeO.OI)'6.0xAsJ _~bo.05)Jrx;SJJ.oo. cervelleite (Ag1.8-CIIO_86Z"o_ol)r6(Teo8~o.J4hooSJ.}1 and most probably skinnerite (?) (CuJ .7sAgur;luuaJ1.1o(Sbo.uTeo .:~O -~}9.1 are found as fine inclusions in galena.

Total quantity of silver-bearins minerals and phases could not fit high average content of AS in the ore. It seems that main carner of Ag is salena. Average content of Ag in galena for different deposits (AAS ana lyses data) val)' !Tom about 200 up to over 3000 ppm (Kolkovski et aL, 1996; Kolkovski and Dobrev, 2000). Recent study reports similar results and in controlling cemented polished briquenes no any mineral inclusions among galena are observed even at very high magnification (both in optical and electron microscope). From the other hand extremely high content of Ag (to 1.23%), Sb (to 088%) and Bi (to 2.64%) in galena is established (microprobe analyses) without discovering any different mineral phases. Content of AS in gale"a shows very goad correlation with summarised content of Sb and Bi -these three elements most probably presem here as solid solution of miargyrite and matildite, or as very fine "micro-domain" inclusions ofthese minerals.

Clear vertical zonation in distribution of main trace elements in galena is traced out. Galena is enriched in Ag and Sb and poor in Bi in the upper levels and in the lower levels it contains Ag., Sb and is with higher Bi content. In cases when content of Bi in galena reaches its local maximum it marks the bonom of ore mineralisation - beneath it barren quartz is situated (Kolkovski and Dobrev, 2000). It should be mentioned that in aII operating mines galena geochemical characteristic is typical for upper level.

References Kolkovski , B. and Manev, D. (1988). Technika, Sofia, 37-63, (in Bulgarian). Kolkovski , B , Dobrev, S., Petrov, P., Manev, D. (1996). Proc. AIIII. Meel. IGCP Pr~ieci 356,

Univ. Minins Geol. Sofia, v. 2, 157-174. Kolkovski, B and Dobrev, S. (2000). ABCD-GEODE Workshop. III: gllidebook la exc. B,

Univ. Mining GeeI. Sofia, 18-36

CUROM1TE MINERALlZATlON: IMPLlCATlON FOR TU E GEOTECTO NIC S EITING OF OPHIOLlTE C OMPLEXES IN THE BALKAN PENINSULA

Maria Economou-Eliopoulos

University of Athens, Depanment of Geolagy, Panepistimiapolis, e-mail : meconom@geol.uoa ar

Petrological and geochemical characteristics indicate that the majority of ophiolite complexes in the Balkan peninsula have been fonned in marginal basins, being a remnant of fore-arc, island arc ar back-arc basin. High-temperature defonnation (ductile and brittle) superimposed on primary magmatic textures during obductian, and retrograte hydrothennal metamorphism are common. An overview of new and published mineralagical and geochemical data pravide evidence for the better understanding of the factors controlling the chromite minerallization, and enstablish relationship with their geotectonic setting. The geochemical features of mantie peridotites of individual ophiolite camplexes hasting large chromite deposits of high-AI or -Cr type in Greece and Albania, are highly depleted mantie Ihat exhibit porphyroclastic textures resulted from recrystallization during repeated cyeles of plastic flow and partial melting. The trace element contents, in orthopyroxenes and clinopyroxenes from the Vourinos, Othrys, Pindos and Bulqiza harzburgites (tectonites), along with the major element composition of pyroxenes and ca-existing Cr#spinel ratios indicate that there is ofien a diversity between the rare earth element (REE), Ti and Zr contents and Cr#spinel ratios suggesting that their composition has been affected by both the degree of partial melting and interaction between mantie peridotite and meh (Zhou el al. , 1998). However, the PGE-panerns for chromite concentrates fram harzburgites, in general, have lawer Os, Ir, Ru and higher Pl, Pd content compared te chromite ores and chromite concentrates from dunites of each complex, resulted tlat PGE-panems consistent with their residual, primitive character. The composition ofthe chromite ores is chacterized by a limited variatian and higher average V and/or Ti in high-Al than in high-Cr chromite deposits in individual ophiolite complexes, which is consistent with a lower degree of panial melting andJor more fertile mantie scurce in the case of high-AI than in -Cr deposits. AIso, large chromite deposits of metallurgical type (high-Cr), (Vourinos in Greece, Bulqiza in Albania), and refTactory type (hiSh-Al), (Othrys in Greece), are restricted to SSZ ophiolite complexes with island arc and back-arc geotectonic environment, respectively. (Ohnenstener el a., 1991 ; Economou-Eliopoulos et al., 1999).

The presence of both high-Cr and -Al types in a spatial association, and comparable proponion, derived from primitive and fractionated ta some extent magmas, is a common feature of relatively small chromite occurrences of the Pindos complex, the central pan of Vourinos (Kissavos), Radiani massif, Euboea and Skyros island, and in Serba-Macedonian and Rhodope massifs (in Greece and Bulgaria). Such chromitites have probably formed fram separate parent magmas of tholeiitic and boninitic composition for the high-AI and -Cr respectively, in a fore-arc, along a transform faul t, geotectonic environment.

Therefore, the mast promising ophiolite complexes are those which in addition to hydrous parent magma (island arc Of back-arc geotectonic environment) contain only one chromite ore type (high-Cr a r -Al) of limited compositional variation and low ratios of incompatibleJcampatible elements.

References Economou-Eliopoulos, M., Tarkian, M .. & G. Sambanis (1999): On the seochemistry of

chromite ores from the Pindos ophiolite complex., Chem. Erde 59: 19-31 . Ohnenstener, M., Karaj, N., Neziraj, A., Johan, Z. and Cina, A. (1991). Le potential

platinifere des ophiolites: mineralizations en elements du groupe du platine (PGE) dans les massifs de Tropoja et Bulqiza, Albania. C.R. Acad. Sci . Paris, 313 (n): 201-208.

Zhou, M.-F. ,Sun, M., Keays, R.R. & Kerrich, W. (1998). Controls on platinum-sroup elemental distributions of podiform chromitites: A case study of high-Cr and high-AI

55

chromitites rrom Chinese oragenic belts Geochimica el Co~mocJ1fIJllca Acta, 62. 677~ 688.

FACTORS CO TROLLING THE Pd, p , and Au POTENTIAL 1 PORPHYRY Cu ± Mo OEPOSITS OF GREEeE AN O BULGA RIA

Maria Economou-Eliopoulos1; Demelrios G. Eliopoulosz

IAthens Univesity, Dept. ofGeology, Panepistimiopolis, e-mail : meconom@geol.uoagr llnstitute of Geology and Mineral Exploration, Athens, e-mail" eliopouJoS@igmegr

The porphyry-Cu ± Ma deposits in Bulgaria (Srednogorie metallogenetic zone) aod in northern Greece (Veniskos Formation of the Serba-Macedonia" zone) belong ta the Carpatho-Balkan metallogenetic system They have formed al convergent plate margins, above zones of active subduction. The crust contributia" ta the paTent magmas of these porphyry intrusions is a common feature.

Compilat ion of some new data on palladium, platinum, gold and silver metal and associated trace element content in mineralized porphyry-Cu ± Mo intrusions (Skouries deposit in Greece, Elacite, Medet, Asarel and Tsar Assen in Bulgaria), and published data indicate rela'ively high Pd ± Pl contents (Eliopoulos e' al., 1995) The ,verage Pd, Pl, Au and Ag contents in the Skouries mineralized porphyry (potassic. propylitic and silicification altera,ion 'ypes) and highly mineralized portions are 110 ppb, 30 ppb, 2700 ppb and 3 ppm, respoc,ively, although as high as 600 ppb Pd, 150 ppb Pl, 9600 ppb Au and 12 ppm Ag have been recorded

Mineralogical and geochemical data. coupled with textural relations between base metal sulphides, PGM and Au-Ag tellurides, indicate that the main Pd-bearing mineral merenskyite, is associaled with chalcopyrite or bomite Assuming that Pd is mainly associated with chalcopyrite in porphyry-copper deposits, calculating, the measured Pd contents in chalcopyrile (measured contenls are normalized 10 100 percent chalcopyrite). then Ihe Pd values in the mineralized samples from the Skouries deposit is comparable to thal in the chalcopyrite concentrate (2400 ppb Pd to 21 wt%, while the calculated Pt content is 1200 ppb (Econamou-Eliopoulos e' al , 2000) The calcula'ed Pd content ,o 100% chalcopyri,e is higher in the case af,he Mede' deposi, (800 ppb Pd) and Tsar Asen (840 ppb) 'han in 'he Assarel depasi' (100 ppb Pd). The p, con'en' ranges fram 20 ,o 50 ppb, and there is a positive correlation between Mo and Pt Based on the depasit reverses and average concentrations of Cu, Pd and PI, the calculat ion oftheir potential indicate that in the Skouries deposit it is approximately 10 (ons Pd and 2 tons Pl, comparable to that ofthe Santi Tomas 11 deposit, Philippines, while in the Elacite deposit , Bulgaria is 3 tons Pd and 2 5 tons Pt (Economou-Eliopoulos e' al, 2000).

The Pd ±Ft enrichment in certa in porphyry Cu intrusions. like Skouries, suggests that a major crust contributia", possibly by assimilation of the country rocks (amphibolites­metabasahs and ultramafic rocks) al depth, prior to the final emplacement and a very limiled participat ion of meteoric component in lhe hydrothermal circulation system are major controlling factors of lhe precious metal enrichment. AIso, such a Pd ±Ft in porphyry Cu systems seems to be a economic factor for this type of deposit, as a by-product along with Cu and Au.

Rererences

56

'opoulos, D. G, Economou-Eliopoulos, M.t

Strashimirov, S1. , Kovachev, V and Zhelyaskova-Panayotova, M. (1995). Gold, Platinum and Palladium cOlllent in porpyry­Cu deposits from Bulgaria: A study in progress. Geological Society of Greece Sp Publ. No 5, p. 712-716.

Economou-Eliopoulos M. El iopoulos, O., Zhelyaskova-PanayolOva, M.and Perantonis, G. (2000)

Distributian of precious metals In porphyry Cu±Mo deposits of Greece and Bulgaria.Proceedings of the 3rd Conference of Mineral Wealth, Technical Chamher of Greeee, Athens, v. A. ,p.143-151.

Frei, R. (1992). lsotope (pb,Rb-Sr, S, O, C, U-Pb) geoehemieal investigations on Teniary intrusives and related mineralizations in the Serhomacedonian Pb-Zn, Sb+Cu-Mo metallogenetic province. in Northem Greece. Ph.D. Thesis, ETH Zurich, pp. 230.

ELATSlTE PORPHYRY COPPER DEPOSIT, BALKAN, BULGARIA Rela tive age relations of hast rock lithologies, minera lisation, alteration and st ructures

L. Fanger" T. Driesnerl• C. A. Heinrichl

, A. Van Quadt ', Irena Peycheva2

1 Institut fur Isolopengeologie und Mineralogische RohstotTe, ETH Zlirich ~ Museum "Mao and Earth", Sofia

The Elatsite copper porphyry ore deposit is located an the main ehain ofthe Balkan an the northern boundary of the Banat-Sredno-Gore Zone and the Panagyurishte ore district in Bulgaria. The depasit is connected to multiphase intrusion of late cretaceous (92.3 +/-1 .4 Ma) pophyric dikes clase ta the contact ofa Cambrian to Precambrian greenshist-metamorphic 50-

called diabase-phyllitoid rrom the Berkovitsa Group and the middle Paleozoic granodioritic Vezhen intrusion. The deposit is famous for its relatively high platinum and palladium content. In this work it was tried to unravel the relative age relations between hOSl rock lilhologies, structures, ore mineralisation, and alteration from field observations and various laboratory techniques. Field evidence c1early shows at least four distinguishable types of dikes. In terms of mass, a plagioclase-porphyry is the most important. It probably belongs to the first dike generation foliowed by multiple phases of amphibole-porphyry, whieh intruded into the host rock as well as into the plagioclase-porphyry. Simultaneously, dikes consisting almost exclusively of potassium feldspar intruded. Some of them cut amphibole-porphyries and in turn some are cut by amphibole-pophyries. The fourth type is a dark, fine-cryslalline dike. for which no direct cross-cuMing relationships with other types could be observed. Since it is mineralised and shows some potassic alteration similar to the other dike types, we can assume thal it intruded al the same time. The mineralisation and the alterat ion respectively started with magnetite veining connected with a potassic alteration. The magnetite slage possibly took place before dike intrusion because it is absent in the dikes. The potassic aheration accompanies also the following chalkopyrite+magnetite+bomite paragenesis. which is the carrier of the platinoids and partly of the gold. At this stage a part of the dikes already intruded as some of these shows Ihis parageneses. While the typical stock work porphyry veining took place, the intensity of potassic alteration decreased and chalcopyrite. pyrite and molybdenite were precipitated. The last dikes intruded during this stage as evidenced by a reduced degree of potassic alteration and quanz vein density. Subsequently. veins of massive chalkopyrite-pyrite were formed and later the deposit is overprinted by a feldspar destructive alteration (maioly sericite), which Îs also seeo along thick (1-30 cm) massive Quartz-Pyrite veins. Late subvenical, Wl\.l'\V-ESE striking Faults cut and displaced

l7

aII the lithologies and caused remobilisation of ore al least along the tWQ major faults and same smaller ones

TRE TENNANTITE ~ ENARGITE EQUlLIDRl UM ANO THERMOOYNAMIC PROPERTIES OF ENARGITE ANO BORNITE

Alexander Filipov, Kamen Bogdanov Depanment of Mineralogy, Petrology and Economic Geology. Sofia University "'Se Kliment Ohridski" I 000 Sofia, Bulgaria

On the hasis of the natural mineral assemblages. observed in epithermal volcanic -hosted sulfide deposits from the Panagurishte ore region (Sredna Gara zone, Bulgaria), it has bee" conc1uded that, al least pa"ly. the tennantite <::) enargite equilibrium must lie in the stability field of bomite. Using the thermodynamic data for tetrahedrite-tennantites, derived by Seal et al. (1990), and for the equilibrium chalcopyrite ~ bomite + pyrite by Banon & Skinner (1979), we obtain for the standard Gibbs free energies of formation of enargite and bomite from pure elements and ideal diatomic sulfur gas AC?ftUl} = .437052 + 116.74 T O/mal , T in K) and tJ.G""", = - 593910 + 185.74 T (J/mol), linearized at 250 'c respectively Ca1culated with these expressions. the sulfur fugacities of various equilibria in the temperature range 200 - 350 °c show that the upper limil of stability of tetrahedrite· tennantites is governed by the equilibria Zn·tennantite ..;. chalcopyrite ~ enargite + sphalerite + pyrite and Zn·tennantite + bornite ~ enargite + sphalerite + pyrite in the stabi lity fi elds of chalcopyrite and bomite, respective ly, and lies at log/S, = - 8.6 at 250 'c. These equi libria show lin ie temperature dependence and can be used as a good indicator fo r sulfur fugacity in a wide temperature range.

Notwithslanding the fact that data for both A(f, of enargite and Cu·tennantite. reponed by Graig & Banon (1973) have Jarge uncenainties. there are no large discrepancies between our results and the tennantite ~ enargite equilibrium calcuJated with these data al a temperature higher than 250 °c . They are nearly of the same order of magnilude al 250 °C and nearly equal al 300 °C.

Our fi ndings agree well with the gold composition (Au,.Ag .. ), reponed from the Cu ­sulfide slage of mineralizalion in lhe epithermal VHS deposits Elshitsa. Raka, Krasen and CheJopech from the Panagyurishte ore region in Bulgaria.

FLUID I 'CLUS IONS MICROTHERMOMETRY AND CATHOOOLUMINISCENCE IMAGES ON THE EPITHERMAL Q UARTZ FROM SĂCĂRÂMBlNAGY AG/GRODASTDORF - BOCSA MAREIBOKSA-BĂNY A CORANDN KORANDA SUBVOLCANI C AREA

Agnes Gal Department of Mineralogy, Babeş-Bolyai University, Cluj , Kogălniceanu nr. 1., RO-3400, Romania

The present work a«empts to give additionaJ information on the connection between cathodoluminescence images and physico-chemical circumstances of crystalliz8tion in the case of hydrothermal quartz.

l8

GeoJogica l context The studied crystals \\ere obtained from law sulphidation veins, geodes and breccias in the

eogene Brad-Sacarâmb Basin from the following localities. Sacarâmb (GroBastdorf, Nagyâg), Bocsa Mare (Boksa-bânya), Coranda (Koranda).

LA·ICPMS :1nalyses of fluid inclusions: Fluid inclusion studies were dane on a USGS heaeing-cooling slage.

Results: The main results are the following: homogenisation temperature is between 147-333°C (Th), the IasI iee crystals disappear al -4. I-Q.goC (Tm,Of)' Calculated salinity is 0.5-8 eq. \VI % . aCI [1].Two types of inclusions were round. Liquid-rich and vapour-rich inc1usions appear with the same frequency in aII the analyzed crystals. The ThfTm"cdiagram ofHedenquist and Henley [3] indicates the beiling offluids as show al50 by Pimea [2]. Zonation ofthe crystals wa5 evidenced by cathodoluminescence method the diagram.

ConcJusions: The results suggest a correlation between quanz cathodoluminiscence images and the cond it ion of crystall ization in the case of the crystals studied

References [1 ] Bodnar, R J , (1 993): Revi5ed equation and table for determining the lTeezing point

depression ofH20-NaCI solutions. - Geochimica et Cosmochimica Acta, 57, 683-694 [2] Pintea, 1, (1 993) Fluid inc1usions microthermometry. Some typical examples. - Rom. J.

Mineralogy, 76/ 2: 25 - 36. [3 ] Hedenquist, J W & Henley, R. W , (1985)· The imponance of CO, on lTeezing point

measurements in fluid inclusions: evidence from active geothennal systems and implicat ion for epithermal ore deposition. - Econ. Gool. 80 1379 - 1406.

LEAD ISOTOP E SIGNATURES O F EPITHERMAL ANO PORPHYRY-TYPE ORE OEPOSITS FROM BAlA MARE OISTRJCT ANO APUSENI MO UNTAlNS, ROMANIA

Luminita Grancea', [rie l\1arcoux1, Marian LupulescuJ

, Jean Pierre Milesr.t ) UMR G2R. Universite Henri Poincare, 54500 Vandoeuvre cedex, France 2 ISTO, Universit. d'Orlean5, ESEM, 45072 Orleans cedex, France 3 University of Bucharest, Romania 4 BRGM DRlMESY Orl.ans, France

outhern Apuseni Mountains (so-called 'Metaliferi Mountains') and Baia Mare district bave a 10ng his tor)' of mining and were particularly famous for gold ore deposits. Ore deposits are mainly epithermal (Iow-sulfidation) veins (Baia Mare et Apuseni M1S.) and gold rich porphyry-copper ore deposits (Apuseni Mts. ).

Pb-isotopic analys is Samples of various are-minerals and local volcanic country rocks have been collected and their Pb-isotopic compositions have been measured. The major objectives ofthis study were:

59

1) to determine the isotopic compositions of the mineralizations and ta test their possible relationship and 2) ta examine the possibles SQurces of the hydrothermal Pb. Furthermore, these data might provide same additional informatian to undersland the geodynamic rramework ofthe Carpatho-Panonnian region.

Results Baia Mare district and Apuseni Mountains have difTerent non overlaping Pb isotoEic signatures ranging from 18.752 to 18 .876 and 18.497 ta 18.740 respectively for 206pbPo Pb ratias. In the Baia Mare district, epithermal deposits are overall homogeneous in their Pb-i sotopic compositions and have values similar ta the average of the calc-alkaline volcanic rocks. These results 5uggest a magmatie signature for the Pb (and possible other metals) in the hydrothennal fluid ,. In the southem Apuseni Mts., lead isotope composition of sulfide minerals in porphyry copper are c1ustered, confirming that Pb, and probably other metals, were derived principally from associated porphyry stacks. On the other hand, sulfides in epithermal ore deposits are much less scattered, indicating a notable contribution of Pb from local country rocks.

Conclusions '-n the Apuseni Mts ., ' fertile' volcanies are few and appear ta derived from a more primitive mantle-derived souree. Most of the volcanie rocks analysed seems barren. DifTerences in Pb­isotopic compositions belween Baia Mare district and Apuseni Mts. are due ta a different basement, and probably due ta variations in crustal assimilation superimposed an variations in the mantie source composition. In Apuseni Mts., Pb may be partly inherited from the previous Mesozoic magmatic-hydrothermal stage.

40AR/39AR AGE CONSTRAINTS ON TBE FORMATION OF MESOTHE RMAL AU-QUARTZ-VELNS WITBLN TBE TAUERN WLNDOW, EA STERN ALPS (AUSTRIA)

Robert Handler & Franz Neubauer In,!. f Geology & Palaeontology, Univ. Salzburg, Hellbrunner Str. 34, A - 5020 Salzburg, Austria

Formation of open, crystal-filled extension veins within the Tauern Window of the Eastem AJps (Austria) has been dated 40Ar/39Ar using adularia and white mica. Generally, the formation of these minerals is contemporaneaous to, or post-dates, mineralisation in mesothermal Au-quartz veins. Dating has been carried out an 10 samples ofwhite mica (Ms) and adularia (Kfs), which have been separated from up to cm-Iarge free crystals post-dating mineralisation. AJthough age spectra and 36Ar/40Ar vs. 39Ar/40Ar isotopic correlation plols indicate variable contributions of extraneous 40Ar-components, resu\ts ma)' indicate twO different pulses of vein formation, probably eaused by two independent fluid pulses. We do not observe any correlation between the dated minerals (e.g. Ms ar Kfs) and the ohtained ages, nor with the amount of incorporated extraneous 40Ar components. Because temperarures for vein formation were similar ar lower than cJosure temperatures for the Ar­isotopic system in white mica (c. 400°C). and K-feldspar (c. 20QoC), these ages are interpreted as crystallisation ages, and to directly date the formation ofthe veins.

Tectonic map of the Tauern WJndow IrdlC8hng 40Ar/39Ar sample locaMns and results (p a . plateau age, t 9 a total-gas age, lea iS010pe correlatlon agel

D Aultroalpine umts • Ecloglla zone

~ K~mmka& [JJ S'on napp. E! Matrei zone rn WoIfendom nappe O Glockner nappe Q Rtffl nappe D Role Wand • Modef8ck nappe O Venedtger' nappe

Sample 6 Kfs

60

SImple 4 Kh i H:.It..lt pa "135:t0 2Ma OII

rea 13S:t01Ma

1.98 249:t02Ma Ica . 192~OIMa

Sample 10 Kfs Sample 8 Kfs Sample 7 Kh

i •

pa 159:t:02Ma iea 159:t01Ma

pa 208:t:02Ma iCI205:t:01Ma

pa 203:tOnia iCI 187:t04Ma

Sample 1 Ms pa 151:t05Ma Ica 154:t:06Ma

Sample5Kb pa 169:%::02Ma lea 169:t02Ma

$ample 3 MI .. -- pa " 1593:04Ma

Ica 162:t05Ma

Sample 9 Kfs pa "186:t:02Ma ica 185:t03Ma

Sample2 Ms pa 198:t04Ma iC I 197:1:Q4Ma

Samples yielding an ase of ca 19 Ma have been collected rrom wilhin an area where quartz-Au veins are mosI widespread. We interpret this age 10 closel)' date ore formation during c. ESE-WN\V extension in accomodation zones along the a strike-slip zone thal separates distinct culminations of the Tauem metamorphic dome. The second age group, at ca. 15 Ma, is related to barren veins at upper margins of Ihe Tauem window. This age group is interpreted to represent a distinct thermal pulse which coincides in ase with a weak thermal pulse also found in mylonites. The third ase, al c. 13 Ma, is found in the westem part oflhe Tauem Window and coincides in ase with regional cooling found by zircon fis sion track dating.

NEW MODEL FOR UPPER CRETACEOUS MAGMA EMPLACEMENT IN THE SOUTDWESTERN PARTS OF CENTRAL REDNOGORIE PETROSTRUCTURAL AND AMS DATA

I"anov, Zh.', Henry. B.2, Dimo", O.' , Georgie", N,I, Jordanova, D.l, and Jordanova. N3

•

, Dep. of Gepology and Geography, SI. Kliment Ohridski University, Sofia 2 Lab. ofGeomagn. and Paleomagn., IPGP and SNRS, Saint-Maur, France l Geophysical Institu,e, Bulg. Acad. Sci .. Sofia

Subject of the present Sludies - petrostructural and magnetic (AMS) is a chain of intrusive bodies situated in southem Bulgaria in the border area between the Rhodopes and the Central parts of the Srednogorie Tectonic Zone. The plutons from this chain - Gutsal, Varshilo, Boshulia, Elshilsa and Lesichovo are of granitic composition (granodiorites and graniles). There are comparativel)' large lenselike bodies and sheets from basic rocks (gabbro and gabbro-diorites) embedded in them. The existing literature sources, treating the petrology, structure and conditions of the bodies' formation, regard the origin of the plutons as a result

,.\

oftWQ temporally divided magmatic epochs - Paleozoic (Variscan) and Late Cretaccous. The Late Cretaceous plutons are characterized as "fissure plutons" intruded in c>.1ensional riA. setting.

The obtained results refer us ta essential revisions of the existing interpretations. The mOSI important ones ca" be summarized as follows:

1. The observed field relations, the character and orientat ion of the microstructures and the AMS elements (magnetic foliation, magnetic lineat ion, anisotropy degree, etc.) in the ÎntrÎsives and the hasi rocks anest to Oile genetically assocÎalcd Late Cretaceous syntectonic magmatic complex, that originated in regional transpresional geological setting.

2. The mosI important tectonic element thal predetermined the magma emplacement, the structure of lhe magma chamber (or chambers) and the development ofthe later imposed (solid-state) deformations is a weB pronounced shear zone trending NW-SE - Iskar-Yavoritsa Shear Zone (lYSZ). In ils limits as well as in the associated sub-parallel ar synthetic second order shear zones an entire conformity between the magmatic and the imposed high­temperature andlor middle temperature microstructures and magnetic structural elements (folialion and li neation) is estab li shed. They themselves also represent belts of the hig hest magnetic anisolropy degree (P) .

3. In regional sca le magma emplacement was accomplished in complexly arranged laccolith-l ike chamber, additionally intrÎcated by the syn- and post-magmatic strike-s lip deformations, which development continued afier the main phase of magma crystallization. Some of the plutons (especially those situated in the northeastem block of the IYSZ) passes Ihe characteri stics of well-Iayered inlrusions: their lower pans consist of crystal phase rich (mosI ofien porphyry) granodiori tes and graniles, and the upper - from felsie , crystal phase poor granites . Between these two parts comparalively thin levels (thickness 200-300m 10 1-1.5km) representing Ihemselves sheet-like bodies composed rrom gabbro or gabbro-d iorites (Ihiekness of 40-50 to 60-70m) and placed above them swarms of basÎC enclaves emerge clearly. The load easts textures and the "pipe" structu res along the lower pans of the basic sheet-like bodies and Ihe traees of eonveetion movements in the swarms of the basie enelaves, testify ta a si ll-like emplaeement ofthe basic magma into part ly crystallized layered magma chamber. The basie magma (coming from the deeper crust levels) permeated a long the lYSZ (deeply penetrating shear zone). The regional position of the adjacent to the shear zone basic sheet-like bodies and the orientation of the magnetic fo liation and lineation indicate this. AII these data give a good ground ta consider the magmatic complex as result of a bimodal magmatism and example of two types magma mixing - granitic and basic. It is consistent wilh the bimodal character of the Late Cretaceous volcanic activity revea led ta the north in the vicinity of lhe investigated area in Ihis part oflhe Srednogorie Tectonic Zone.

MULTIATRIBUTIVE PROGNOSIS ESTIl\1ATION OF CU IN TElE NORTI:lERN PART OF BOR METALLOGENIC ZONE (CARPATRO-BALKAN METALLO­GENIC PROVlNCE)

Rade Jelenkovic l, Todor Serafimovski1

, Ot'jan KozeljJ IFaculty of Mining and Geology. University of Belgrade. FR Jugoslavia 2Faculty ofMining and Geology, Vniversity ofSkopje, R Macedonia 3Copper Institute. Bor, FR Jugoslavia

The scope of this paper is a review of de\'elopment methodology the prognostic map of copper mineralization of northern part of the Bor metallogenic zone by the use of

62

MAPO progra m package. The separation of surfaces with various degree potentiality regarding Ihe porphyry capper and massÎve sulfide type of mineralization was carried ou t aud a proposal of areas for necessary further geologic prospectings.

Analytical process of prognosticating mineral resources al a panicular terrain is based a n recognition of different indicat ars, namely features (geological , geochemical, geophysical etc.) as well as an correlat ive binding ta a cenain type of deposits and metallogenic environment. PrognoSiication is grounded an the very concept of balance, what understands definitian of the overall relative significance of groups of features (attributes), and relies generally, within this process, an both geological information on characteristic features of mineraJization and information on specific features for the particular type of deposit and metallogenic environment.

This may be reached by structuring a prognostication problem, the salut ion of which requires involvement of severa! experts with the aim to detine objectively the criteria to detennine degree of significance to attributes, general ize preferences for a single group of attributes, state precisely a composite - nonnalized vector of estimation, and detine ranks and composite vectors of prognoSlication.

In principle, prognostication represems an extremely complex process due, as a rule, to a fuzzy nature of indicators, incorporation of numerous attributes and complex correlation bonds.

This indicates a conclusion that it is impossible to authomatize completely the process of prognoSlication using mathematical - modelling and computerization, and that a pragmatic solution of the problem should be found in a hybrid approach by combining expert knowledge and logistic support ofTerred by mathematics and computer technics.

Those are principles the Method ofmuhiatributive prognostication, abbreviated to MAPO.

TERTIARY GEOTECTONIC EVOLUTION AND SUBDUCTION RE LA TED MAGMATISM OF TElE BAIA MARE METALLOGENIC REGION (ROMANIA)

Marinel Kovacs l! Alexandrina Fulopl

11PEG Maramures, 146 Victoriei street, 4800 Baia Mare, Romania 2North University Baia Mare, 62A V. Babes street, 4800 Baia Mare, Romania

Baia-Mare metallogenic region represents ODe of the mos t important vein-hosted polymetallic and goJd-rich epithermal district in the Carpat ho- Balkan area. The metallogeny of the Baia Mare region (BMR) is assoc iated 10 the Miocene subduction­relafed magmatism, developed in fhe Oas-Gutai MU. (Eastern Carpathians).

A CA rhyolitic volcanism developed in the south-westem part of the Gutai Mts, emplacing caldera-related high-grade ignimbrites overlain by a sequence of volcaniclastics and sedimentary deposits. The 15,4 Ma CA rhyolitic volcanism correlates with the MiddJe Rhyolite TufT from the Pannonian Basin, being a consistent part of the areal extensional acidic volcanism. Ils onset reOecls the hinterland reply of the initial slage of subduction, explained by lhe Sleeper dipping of lhe Subducling slab roll-back (Nemcok el al, 1998). An

features of hydrothermal solutions and surrounding environmenl. Al the most important associated component in copper deposits in the Bor metallogenetic zone gold occurs.

The paper will present only the deposits and the occurrences in the Bor metallogenetic zone where gold appears as the imponant supporting componenl. Various types of copper mineralization have been selected : pophyry deposit , hydrothermal-vulcanogenetic deposits in the forms of stock or lentil (with massive sulphides), hydrothermal - vu lcanogenetic deposits in the form of vein (with deposited and impregnated sulphide minerals), mechanically overdeposited sediments (formed by disintegration of previously formed massive sulphide deposits) and skarn deposits. The main features of the mentioned deposits will be presented, alteration mineralogy zoning in their adjacent vicitiny and compared with the similar deposits and occurrences in the Timok eruptive area. Key words: copper, gold. mineralizations, hydrothermal, porphyry, andesite.

MAGMATIC EVO LUTION AS A KEY TO UN DERSTAN DLNG TR E VA RIASILlTY OF EPITB ERMA L SYSTEMS

J it roslav Lua Geological Survey of Slovak Republic, 817 04 Sratislava, Slovakia

The evolution of magmas in shallow crustal chambers and the emplacement of subvolcanic stocks are th e key fa ctors controlling the "ariabil ity of epithermal systems.

Epithermal systems show agreat variability of styles and geological settings, refleeting variability of fluids composition and their sources. There are generally distinguished: (1) mineraJized or barren high-sulfidation (HS) systems, associating mostly with high level subvolcanic porphyry stocks in andesitic terrains; (2) intrusion-related low-sulfidation (LS) systems associating closely in space and time with former ones; (3) LS systems in andesitic terrai ns without such the relationship; (4) LS systems associating with the rhyolite voleanic activity. Details and genetic aspects are covered extensively in numerous review papers (e.g. Sillitoe, 1993; Hedenquist and Arribas, 1999). However, there are three important aspects to be considered here: (1) panitioning of high temperature saline fluids into gas-enriched low salinity vapor and hypersaline brine at pressures less than 0.5 - 1.5 kbars depending on temperature (2 - 6 km at lithostatie pressure); (2) rather low salinity of primary magmatic fluids at the order of 2 - 10 %: (3) volume of magma contributing metals to the average size ore deposit is at the order of 100 - 200 km' - it is the subvoleanic porphyry stoei<, which is ehanneling fluids.

In view ofthese facts we can explain the mentioned variability of epithermal systems in terms of the magmatie evolution: (1) First of aII, epithermal mineraIizations will associate only with those volcanoes, whieh have reached the maturity stage associated with the formation of the shallow crustal magma chamber and related subvolcanic intrusions. (2) Emplacement of a high level subvolcanic stock into the region of saline fluid panitioni ng creates conditions for the evolution of the HS system, as well as the complementary Cu­porphyry system and intrusion reJated LS systems. Due to a progressive erystallization of the stock and a decrease in temperature, the early stage marked by the vapor-brîne panitioning and related advanced argiJlie alterations of the HS system is followed by the slage of deeper fluid separation and possible di lution, giving rise ta mineralization itself (Shinohara and Hedenquist, 1997). Ifdiluted by meteorie waler and reduced by interaetion with rocks. these fluids give rise ta the intrusion related LS systems. (3) Emplacement of a deeper level stock,

65

below the region ofsaline fluid partitioning, \ViII nDt create conditions for the evolutian ofthe HS system. Instead, it will reproduce directly the second slage of the high level porphyry stock (see above), reduced an diluted magmatic fluids giving rise to Ihe LS systems nOI

related to contemporaneous HS and Cu-porphyry systems. (4) Longer Iiving shallow crustal magma chambers evolve via AFC processes towards silicic composition - with ar withoul a preceding slage of andesitic volcanism. This type of magma chambers supplies fluids ta the third type ofLS systems associating with rhyolite volcanic activity.

References Hedenquist, J.W. and Arribas, A. , 1999 Epithermal gold deposits: 1. l-Iydrothermal processes

in intrusion related systems, II Characteristics. examples and cogin of epithermal gold deposits. In : Molnar, F., Lexa, J. and Hedenquist , J.W., eds., Epithermal mineralization ofWestem Carpathians. Societyof Economic Geologists guidebook series, 31, 13-63.

Shinohara, H. and Hedenquist. J.W , 1997: Constrains an magma degassing beneath the Far Southeast porphyry Cu-Au deposit , Philippines. Joumal of Petrology, 38, 1741-1752.

TEMPORAL AND ISOTOPE (SR, PB, O AND D) EVIDENCE FOR MAGMA T1C­DOMINATED EPITRERMAL ACT1VITY AT TRE MADJAROVO BASE­PRECEOS METAL ORE DEPOSIT (EASTERN RRODOPES, BULGARIA)

Peter Marchev l, Brad Singer, Bilary OownesJ

, Robert Moritz'" Richard McCoyd.5 'Geol Inst , BAS, Acad G. Bonchev SI., 1113 Sofia, Bulgaria 20 ept Geol Geophys. Univ Wisconsin-Madison, 1215 W Oayton St, Madison, Wisconsin 53706, USA ' School Eanh Sci, Birkbeck College, Univ London, Malet St , London, WCIE7114, UK 4 Sect Sci Terre, Univ Geneve. rue de maraÎchers 13 , 1211 Geneve, Switzerland ' Dept Geol Petrol Geol, Univ Aberdeen, Aberdeen, AB9, UK

The Madjarovo are district is located in the volcanic rocks of the Oligocene Madjarovo volcano and underlying pre-Mesozoic high-grade metamorphic rocks of the Rhodope massif. Alteration (K-silicate and advanced argillic) and mineralized low-sulfidation veins show unusually close and clear spatial relationships with panicular magmatic bodies providing excellent bases for studying the temporaJ relations and source(s) of fluids and metals in the intrusion-related low-sulfidation syslems.

Timing and duration ofthe magmatic and hydrothermal events at Madjarovo have been dated by single-crystal and step heating laser-probe 40 AIţl9 Ar measurements of K-bearing minerals from the host rocks and alteration. The resuhs show that adularia-sericite base and precious metal deposit (32.15 Ma) is hosted in slightly older (32.6-32.2 Ma) shoshonitic and high-K calc-alkaline lavas and their intrusi ve equivalents, being cJosely temporally and spatially related to the late monzonite-trachyte intrusions (32 23 Ma).

To investigate the possible role of different sources and genetic link between magmatic evenlS and associated low-sulfidation mineralization, radiogenic (Sr and Pb) and slable (O and O) isotope compositions of gangue, ore, and alteration minerals were studied and compared with the host igneous and metamorphic rocks

The 87Srf6Sr compositions of 5 barites from different veins fali in the range 0.70854-0.70955. The Jowest and highest values are found in smaller brecciated veins, reflecting effective fluid-rock interaetion with either host metamorphic ar volcanic rocks. The isolope composition ofbarites rrom large veins is homogeneous (0.70884-0.70899). It is independent

67

The outer endaskam lones have a massive metasomatic texture aod are mainly composed by medium to coarse gehlenite (up to 98% from the volume ofthe rock). The solid solulions loward âkennanile vary from Ak 22.90 10 Ak 36.28 (mean Ak 29.80) al CH, from Ak 33 .64 10 Ak 38.13 (mean Ak 36.22) al MV and from Ak 31.5610 Ak 49.59 (mean Ak 39.88) at ac respectively. The rock additionally contains monticellite. grossular-andradite, wollastonjte (the 2M polytype), hydroxylellestadite, vesuvianite, pyrite aod secondary minerals such as hibschite. thomsonite, tobermorite. calcite and alJophane. Monlicellite oecurs as very 5ubordinate phase « 0.5%) al MV and CH, while it is more important alOC. It occurs either as interstitial subhedral gr8ins between gehlenite crystals or as fine-grained aggregates in larger interstices alOC. The chemical composition of a representative sample from OC corresponds to a terrn with 8.61 mol.% kirschsteinite and 1.47 mol.% glaucochroite in solid solution The gamet in equilibrium with gehlenite covers a large interval of grossu la r - andradite solid salut ion and has low Ti content (up to I wt .% Ti02) . It generally occurs as inclusions in gehlenite and rarely within the geh lenite crystals as atoll-disposed star-shaped crystals. Zoning is rare, and analyses vary chiefly between Grs 74.81 and Grs 88.52 al CH, between Grs 67.48 and Grs 87.16 al MV and between Grs 34.22 and Grs 69.67 alOC. Subsequent generations of Ti-rich gamet characteristically oecur al CH and MV. l:lidroxylellesl3dite is scanered at random throughoul the gehlenite groundmass The average composition of a representative sample from OC gave the structural formula : (Ca. ."Mgo ,..Mn()(lO ,Fe'· . oo.Nao.mK" oo,)(Si, ",S, , .. p •• 82)[O"7I7(OH), , .. F •• "CI •• ,,].

The compositional data combined with experimental established and caJculated equilibria accounts for crysta lli zation of the main paragenesis in the endocontact zone at temperatures of - 750°C, that perfectly agrees with the temperature estimated for lhe dioritic magma.

BRECCIA TY PES IN BAIA SPRfE POLYMETALLlC-GOLD DEPOSIT

Angela Mihalachel, Cornel C hiuzbaian2

I Geologicallnstitute of Romania, Bucharest, e-mail : angelam@igr.ro 2 Exploatarea Miniera Baia Sprie, judet Maramures, Romania

Our investigatians conceming Baia Sprie epithermal structure evidenced the presence inside the Principal Vein of various breccia-types closely related to the hydrothermal processes that have been effective in this structure.

Geological contul. Baia Sprie structure is located in the Neogene volcanics (Jereapan pyroxene±amphibole-bearing andesiles) and in the Pannonian sedimentary from the southem slope of Gutai Mauntains, pa" of a 8 krn-Iong graben controlled by Dragos Voda strike-slip faull.

Methods. Breccia typology and the relations betwcen difTerent breccia types have been studied at macroscopic and microscopic scale. The study is based on 31 samples collected from three zones of the Principal Vein , located, from west to east: (a) Ramura-Put Terezia­horizon XVI ; (b) shaft 5 - horizons X, Xl , Xll ; (e) shaft 6 - horizon XVI.

Results. The investigations evidenced the following breccia-types: 1. Polygenous unmineralized breccia is built up by cJasls of Jereapan pyroxene±amphibole­bearing andesites and, subordinatedly, by dacites / rhyolites intensely hydrothennally altered,

68

and, sporadically by black mari and coa1y mari c1asts. The matrix consist of black-coloured fine grained mari with fluidal appearance and contains sedimentary and andesite lithoclasts. II . Cupriferous breccia is made up of a banded prevalent cupriferous matrix (chalcopyrite, pyrite±galena and sphalerite) with quanz and carbonate gangue. which cements andesite and mari and sandstones c1asts. III Polymetallic-hydrolhermal (ti lonian) hreccia consists of cupriferous breccia clasts cemented by a mainly polymetallic matrix (sphalerite. galena, pyrite, subordinatedly chalcopyrite in a gangue of quanz. carbonate. sometimes associated with stihnite. plumosite and realgar) . This breccia tipe is c10sely related to the Principal Vein formation. [V. Tectonic breccia has heen found along the Principal Vein, at ilS nonhem contact with the boSI andesite and/or the Neogene sedimentary. The breccia is made up by rounded and s­shaped andesite and sedimentary elements hosted into a milanitic silicified and carbonated matrix impregnaled with pyrite.

Conclusions. 1) Two main stages may be remarked in the evolution of the metallogenetic processes of Baia Sprie structure: (a) the emplacement of polygenous breccias accompanied by a prevalent rupriferous mineraJization and (b) the opening ofthe Principal Vein associated both with the re-brecciation of cupriferous mineralization and with the generation of the polymetallic, goJd IOd silver mineralization. 2) Based on the breccia body shape as well as of the clast and matri x composition, the polygenous breccias may be assigned to the "breccia pipe" type. 3) Shear-type faliation that affected the hydrothennal and cupriferous breccias seems ta be the result of the same deformational event Ihat generated the tectonic breccias. 4) So far there is no strang evidence ta indicate a direct reiat ion between the breccia pipe bodies and an intrusive subvu1canic body.

HYDROTEIERMAL ALTERATION ASSOCIATED \VITEI TElE ROLCANA PORPElYRY CU-AU ORE DEPOSIT (METAUFERI MOUNTAlNS, ROMANIA)

Viorica Milu l, Patrice Pian ton el, Jacques Leroyl, Gheorghe Udubasa l

, Emil Constantinescu"' 1 GIR, Caransebes SI. 1, 79678-Bucharest , Romania, e-mail : vmilu@igr.ro; ' RRGM, DR/RM, BP 6009, 45060 Orleans cedex 2, France; ' UHP-Nancy 1, UMR G2R, BP 239, 54506 Vandoeuvre les Nancy cedex, France; ~ Bucharest University, N. Balcescu Bd., 1, Bucharest, Romania

The Bolcana porphyry Cu-Au deposit is located in Metaliferi Mountains (westem Romania). It is an intrusion-related mineralised hydrothennal system associated with a subvolcanic body (Bolcana microdiorite) of Sarmatian age, which intruded mainly Miocene volcanic rocks (Hondol-Faerag andesite) (BoSlinescu, 1984).

The alteration minerals were identified by optical microscopy, electron micraprobe analyses, scanning electron microscopy and X-ray diffractometry. Major and trace elements of sampled rocks were analysed by ICP method and Au by atomic absorption spectrophotometry.

The distribution of copper mineralisation and hydrothermal aheration show a close spatial relationship to the Bolcana porphyry. Four alteration types (potassic, phyllic, argillic and

69

propylitic) \\fere separated (Milu, 1999). The potassic alteration is developed in the deepesl aod innermosl pan ofthe intrusive body: it grades upward either ta phyllic aod then ta argillic alteration ar directly ta argillic alteralion. The phyllic aheration is developed al a Jow level aod the characteristic minerals both crystallised in veinlets aod replaced the pre-existing minerals in wall rocks. The argillic alterat ion (intermediate argillic type) affected the upper pan ofthe Bolcana system. Fissures bearing alteration minerals characteristic ofphyllic and argillic alteration crasscut eve" the deeper pan of the porphyritic intrusion. The propylitic alteration oecurs like a broad halo of the other alteration types aod as reliel islaods to the margins of the argillic alteration zone. The large development of sulphidation (anhydrite ofien replaced by gypsum) and carbonatation (calcite) is a particularity of Bolcana hydrolhennal syslem.

Using mineral chemistry of some alterat ion minerals, their crystallisation temperatures were estimated applying difTerent geothermometers. Taking into considerat ion the values obtained and also the alterat ion zones and the stability domains of specific minerals, the alteration pattern at Bolcana is the result of an overprinting of the alterat ion process. Propylitisation seems to be nearly simultaneous with, but peripheral to, potassic alterat ion. Phyllic alterat ion post-dates the potassic alteration and it is supposed would have formed a reduced halo around the Bolcana intrusion. Argillic alterat ion overprints the other alteration Iypes.

The results of paragenetic studies also indicate an evolution of the system from an early period of porphyry copper mineralisation (mainly chalcopyrite, pyrite, magnetite, hematite. bomite, molybdenite, with subordinate native gold) la a late period of low-sulphidation mineralisation (pyrite, sphalerile, galena, chalcopyrite, tetrahedrite, marcasite. bournonite, arsenopyrite, pyrrothite and native gold). The epithermal mineralisation consists of polymetallic veins in gangue of carbonates aod auriferous veins in gangue of quartz (Udubasa el al , 1978, 1981 - GIR inlemal repons). The polassic aheralion and porphyry copper mineralisation are spalially related and are thought to be formed al mOSI al the same stage with the likelihood thal the mineralisation process continued during later alteratioo process.

References Milu V. (1999) Hydrothermal alterations associated with Bolcana and Rosia Poieni porphyry

copper deposils (South Apuseni Mountains). Unpub PhD Thesis, Bucharest University, Romania, 250 pp.

Bostinescu S. (1984) Porphyry copper systems in the South Apuseni Mountains - Romania. Ann. IGG, LXIV: 163- 175

TBE LATE CRETACEOUS Au-Cu CIlELOPECH OEPOSIT, SREONEGORlE ZONE, BULGARIA: INFRAREO MICROTHERMOMETRY OF ENARGITE, ANO Pb, S., & S ISOTOPE STUOY

R MOritz!, R Petrunov2, M. Chiaradia!! D. Fontigniel

, & A. Arisanovl

I Sectian des Sciences de la Terre, University of Geneva, rue des Maraichers 13 , 1211 Geneva 4, Switzerland 2 Geolagical Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria ) Navan-Chelopech AO, Chelopech Mine, Sofia Dislricl, Bulgaria

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The Chelopech mine is located within the nonhern pan oflhe Panagyurishte Ofe regio" about 60 krn east of Sofia. in the Banat-Srednegorie metallogenic belt. The Chelopech Au-Cu depasit contains a mineralogy typical of precious metal high 5u lfidation epithermal deposits, but also incJudes an early slage of banded massive pyrite ore typically described in vo1canic massive sulfide deposits. Because of these apparent mineralogical and textural ambiguities. the genesis of lhe Chelopech depasit is intensely debated (sec also Chambefan el al ., abstract volume of this GEODE meeting). There is a lack of iS010pic and fluid inc1usion data for constraining ils genesis and to unrlerstand ils relationship with respect to other ore deposits of the Panagyurishte region. In order to address these aims, Ihis contribution presents a microthermometric fluid inclusion study of enargite, and results from a combined Pb, S, and Sr isotope study.

Fluid inclusions ha ve been studied in large enargite crystals rrom open spaces in breccia zones, growing around clasts of the early massive sulfide stage. A few two-phase incJusions were found coexisting with abundant one-phase incJusions. Two-phase inclusions from the same group have high and constant liquid to vapour ratios reflected by si milar homogenisation temperatures. A large number of inclusions decrepitated during ice formation . In other incJusions. the vapour bubble disappeared as ice formed and the bubble appeared suddenly as ice melted spontaneously close te and ofien above O°c. Homogenisation temperatures are grouped between 96 and 131 °C and ice melting temperatures between -2 5 and _7 .2°C. The low homogenisation temperatures are anomalous with respect to bomite-chalcopyrite textures, droplets of native bismuth, and sulfure isolope thermomelrY of barite-sulfide/enargite pairs indicating temperatures of 300°C, greater than 271°C and of 184-241 °C, respectively. as well as the lower temperature limit of the enargite stability field (280-300°C). No primary characteristics can be attributed to any of the inclusions trapped in enargite. It is concluded thal they are secondary fluid incJusions and belong to a younger hydrothermal event thal has overprinted enargile deposition. The one­phase inc1usions are most likely decrepilated inclusions.

The Sr isotope ralios of barite from the Au-Cu orebodies fali belween 0.7077 and 0.7084. They are higher lhan Sr isotope ratios of Upper Cretaceous seawater. and lie in-between the ones of Cretaceous magmatic rocks (0.7045-0.7061) and Paleozoic granites and metamorphic basement rocks (0.7082-0.7155) from the southern Panagyurishte ore region (data from

Kouzmanov et al. , 2001). Sulfides and enargite from the Chelopech deposit yield 0 34S

values between O and -8 %O, and sulfates have C34S values between J 8 and 26 %o above the Upper Cretaceous seawater 0 34S range. The 5 iSOIOpic composition remains constant among difTerent mineralisat ion stages, in particular between the initial massive pyrite stage and the subsequent high sulfidation enargite-gold stage. Early massive pyrite, galena, bomite and enargite from the difTerent stages at Chelopech yield si milar Pb iSOlOpic compositions ("'·Pb/20' Pb= 18.54-18.63; 207Pbl''' Pb= 15 .62-15 .67). The Chelopech sulfides and enargite are more radiogenic than sulfides from similar dcposits of the southem Panagyur;shre regio" (206pb/"" Pb= 18.49-18.53, 207Pbl''''Pb= 15.62_15 64, Amov et al., 1974) and less radiogenic than sulfides from deep-seated Cu-porphyry deposits of the Panagyurishte region. The latler overlap with the Pb isotope data of galenas from the Madan area, Rhodopes ('

06Pbt'''Pb=18.68-18 74, 207pb/20'Pb= 15.66_ 15.68). The Madan galenas contai n Pb mainly derived rrom Precambrian basement metamorphic rocks occurring in the Rhodopes and the Panagyurishte region. The Chelopech Pb and Sr isotope data indicate that hydrothermal fluid circulation during ore fonnation was not only confined to the Upper Cretaceous volcanic host

71

rocks but also extended inlo the basement. and/or that the hydrothennal fluids were derived rrom Cretaceous intrusions that have assimilated old basement rocks. SOlh the S and Pb isotope data reveal that the massÎve pyrite and the high su lfidation enargite-gold stages are two successive events of the same hydrothermal system. The Sr isolope data do not allow us ta determine whether seawater was involved du ring ore formation .

References Amov, B., Bogdanov, 8., & Baldjieva, C. (1974). Proceedings ofthe 4'" IAGOD Symposium,

E. Schweizerbart'sche Verlagsbuchhandlung, Stungart, v. 2, p. 13-25 (in Bulgarian). Kouzmanov, K . Montz, R , Chiaradia, M., Fontignie, D. & Ramboz, C. (2001). Extended

abstract, 6'" biennial meeting ofthe SGA, Krakow, Poland, 26-29 August 2001.

CENOZOIC GEO OYNA MICS OF BULGA RIA AN O ITS RELATION TO O RE­OEPOSITS EVOLUTION.

Radoslav Nakovl, Clark Burchfiel2, Va lent ine KotzevJ

I Geological Institute, Bulgarian Academy of Sciences, Sofia-III), Bulgaria 2 Massachusetts Institute ofTechnology, Cambridge, 02139 MA, U.S.A J CenlTaJ Laboratory of Geodesy, Bulgarian Academy ofSciences, 1040-Sofia, Bulgaria

Major compressional tectonism interspersed with periods of extension occurred within Bulgaria rrom Triassic ta Middle Eocene time. Much of this tectonism can be related to subduction of oceanic crust along the Vardar zone Iying west and south of Bulgaria which ended diachronously in latest Cretaceous to early Cenozoic time. This compressional tectonics is overprinted by the widespread Cenozoic extensional deformat ion ta which until recently little attention has been paid. Many structural and geomorphological features of Bulgaria and the southern Balkan region previously ascribed to compressional events seem to be the result of young extensional deformat ion. Since Middle Eocene time significant extension began within Bulgaria interspersed with short, localized shonening in late Paleogene and early Neogene time. Perhaps the last vestiges of major shortening and subduction along the Vardar zone are represented by the NW-SE trending volcanic arc of Upper Eocene and Oligocene intermediate ta acidic volcanics and shaJlow-level intrusi ve rocks. The metallogenic significance ofthis magmatism is weB known.

Previously data suggested a general normal to arc extension. Newly obtained data show, that contemporary intra-arc extension oblique at a low angle to the arc trend was also presented. This extension was expressed along synsedimentary listric faults with a probable ramp-flat geometry. Stratigraphic and structural data indicate local rotation of hanging wall strata ofup ta 60-80°. These faults are sealed by Middle Miocene sediments, thus pointing ta an Oligocene - ?Early Miocene age of this extension. Often the footwalls of the faults endose a chloritic breccia. Some mineral occurrences and zones of hydrothermal activity also occur along them. During the lai est Oligocene and the earliest Miocene the intra-arc extensian was transformed ta extension that is unrelated to magmatism. This process coincides with the last period of endogenous ore-forming on Bulgarian territory. Since Middle - Late Miocene a new stage of extension has began. This stage is expressed in several steps which have reflected in the forming of numerous grabens in South Bulgaria.

Cenozoic extension is probably polygenetic, driven by complex forces as trench roll­back and gravitational instabilities in an evolving Iithosphere. The latest stages of the process are also influenced by extrusion rrom post-suturing convergence.

GPS data show, thal in the active tectonics of Bulgaria extension is the major form of deformat ion and compression is only locally presented. The derived velocity field implies

73

4. Anhydrite microinclusions suggest that magmatic-hydrolhermal fluids operated under oxidizing conditions. facI supponed also by magnetite presence.

References Drummond S.E., Ohmoto N. (1985) Econ. Geol , 80, 126-147 Heinrich C.A , Gunter D , Audetat A, Ulrich 1 . Frischnecht R (1999) Geology, 27, 755-758 Pintea 1. (1997) ECROFI Xlv"'. Abstr., 266-267, Nancy

SCIlELLGADEN-TYPE Pb-Cu-Au ORES IN TllE SO UTU EASTERN TA UE RN W L'IDOW, EASTERl'l ALPS: RADLG RAB EN TO MALTA BERG

Franz Neubauer1, Gerha rd Arna n" ], \Verner 1-1. Paar 2

I losl . ofGeology, University, Hellbrunner Str 34, A-S020 Salzhurg, Austria 2 Inst. ofMineralogy, University, Hellbrunner Str. 34, A-S020 Salzburg, Austria

Pb-Cu-Au mineralization oecurs within laminated quartzites ( 'Schellgaden-type Au-Pb­Cu-W ores ') of the Kareck complex clase to the upper margin of the Tauem metamorphic core complex, Eastem Alps. The quanzitic ore bodies accur as layer- aod foliation-parallel lenses in various levels of the Kareck complex (e.g. Amann el al. 1997). Ore bodies and counlry rocks were studied on three sites of ancient mining, Radlgraben, Millionenloch and Silberloch (Maitaberg). In aII three localities, the principal lithology is a strongly foliated , fine-grained orthogneiss which is accompanied by up to ten metres thick lenses of epidote amphibolites and greenschists, which mainly occur in lhe footwall of the ore-bearing quanzite. At RadJgraben, a major metadiorite lense is exposed in the hangingwall of the ore­bearing quartzite layer (Tischler and Ucik 1979). The ore-bearing quartzite is in average ca. one metre thick (ca 0.4 - 2 m) and internally laminated. Both outcrop-scale and microscopic characteristics argue for a mylonitic overprint on quartz layers or lenses. AII lithologies, except the metadiorite, are internally strongly foliated with subparallel composite, E-dipping foliation planes. The gneisses bear a weakly developed, well-recrystallized stretching lineation which trends N-S. A second, ESE-plunging stretching lineation predominates and contains a retrograde mineral assemblage, as e.g. chlorite formed on expense of earlier minerals. In a few cases meter-scaled isoclinal folds with limbs subparallel to the composite foliation occur. The fold hinges c10se in eastern side, fold axes trend -S. The second foliation obviously represents the axial surface foliation tO these folds. Pb and Cu concentrations ofsheared rocks are generally lower than that ofundeformed protoliths.

The new data shed new light on the formation of Schellgaden-type Pb-Cu-Au mineralization. The main characteristics are: (1) Ore-bearing quartzites represent a strongly deformed mylonite. No conclusive evidence was found for the formation of ore-bearing quanzites as sedimentary rocks. (2) The ore-bearing quanzites do not represent necessarily a distinct sedimentary layer. AII country rocks represent magmatic sources as indicated by petrographic and geochemical characteristics. Funhermore. the well-preserved metadiorite and the transition into micaceous mylonites suggest the secondary origin of the layering. A possible origin from plutonic sources is still an open question. (3) The shear zone is younger than the metadiorite which is pan of the Variscan basement. (4) Orthogneisses and amphibolites adjacent to ore-bearing quanzites are strongly altered and transformed into schists with hydrous minerals.

We propose, therefore, the following model of fonnation : The Schellgaden-type mineralizations were probably formed or accentuated in ductile low angle normal faults c10se

tO the upper margin of the Tauern metamorphic core complex. The quartzites could have been formed partly by precipitat ion from fluids in open voids during shearing. The origin of metals may ha ve been from basement rocks, e. g. lead mighl have been dissolved by fluid­triggered breakdown of K-feldspar into muscovite and quartz. Amphibolites and dierites may have been the principal seurce for copper. This would also explain the variatien of metal contents along strike of the mineralization. Geological relationships suggest , therefore, a significant contribution to ore formation by late slage orogenic processes along upper margins of the Tauern metamorphic core complex.

References: Amann G., Daxner G., Neubauer F., Paar W.H., Steyrer H.P. (1997). Zentralbl. Geol.

PaIăont. , Teill , 1996: 215-228. Tischler SE, Ucik F. H. (1979). Carinthia Il, 169/98: 371-407.

ACID MAGMATISM IN TOE MAOA N CORE COMPLEX (CENTRAL RHOOOPE, BULGARIA) - NEW ISOTOPE AN O GEOCORONOLOGICAL DATA

Maria Ovtcharova', Albrecht vo n Quadt ', Irena peycheva2, Zlatka Cherneva], F.

Neubauer4, M. Rohrmeier ', C. Aeinrich'

] lnstituteof lsotope Geology and Mineral Resources, ETH-Zurich, Switzerland; 2 National Museum "Earth and Man", Sofia, Bulgaria; ] Bulgarian Academy ofScience, Sofia, Bulgaria; <1 Institute for Geology & Paleontology, University Salzburg, Austria

The Rhodopian massif (Bulgaria) is an element of the Alpine Metamorphic Belt, consisting of collisional napes of metasedimentary and metaigneous rocks (Ivanov at aII ., 1989). The late Alpine extensional evolution oflhe massif is marked by a detachment system connected with exhumation of the granites and migmatites in the core part of different core swells (Madan dome, Biala reka, Kesebir and West Riia Rhodope domes) . The post-collisional extension was followed by graben depressions filled with sediments of Eocene-Oligocene age and active voJcanism and ore mineralization (Zn-Pb and Cu-Pb-Zn ore deposits) . Ore deposits in the Central Rhodopes typically occur În the vicinity of silicic dike swarms. Since some ofthe porphyry dikes show crosscuning relationships with the main detachment and ore veins the absolute and relative timing of deformat ion, magmatism and mineraJization can be used 10 constrain Ihe metal and fluid sources.

During extensienal tectonic conditions main detachment was developing, which caused a separation of the Madan dome into an upper and lower plate. The available geochronological data (U-Pb zircons and Rb-Sr - W.R.) for the lower plate indicate Hercynian protoliths ages (about 300Ma) and an Eocene age of migmatization and granite melt generat ion (36-37Ma, Arnaudov et al. , 1990; Arkadakskiy et al. , 2000; Peycheva et al ., 2000). A Rb-Sr mineral isochron give evidence for a c10sing age of34.5+O.34 Ma (Peycheva el al. , 2000).

New Ar-Ar data an biotite from gneisses ofthe upper plate (eastem part ofthe Madan dome) yield an age of 34.9+0.6 Ma. The same age is reflected by an Rb-Sr isochron (W.R., Bt and Ap) - 35 .22+0.35 Ma. U-Pb analyses on single zircons from mica-bearing pegmatites cuning the biotite şneisses yield a 52Ma. The O-Nd value (T-52, -6.11) is typical for crustal source, while the ' SrI" Sri ratio (0.707051) and zircons O-Hfvalue (-2.26 to - 3.04) indicates young crust and enriched mantie input as a magma source. Based on the isotopic composition of

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lead in the feldspars from the same pegmatites Arnaudov al aiI. , (1974) connecled the origin ofthis pegmatites with mobilizat ion ofmaner al deep levels of old metamorphic rocks

Connected with the mOSI intensively "stretched" sections of the extensia"al system is the formation ofrhyolite dikes al 30.3±3 .5Ma, based on U-Pb analysis on single zircons. The Rb­Sr W-R. analysis ofthe same rhyolites yields an 17Srl"Sr ratio of 0.7065 (T-30Ma) that could be explained with Înpul of mantie material or young crust as well . The C- d value (T-30, -5.3) indicates a crustal scuree of magma generatian. It is in compliance with suggestion Ihat high-grade core of the dame contains intrusions Ihat could be feeders of the volcanism and a150 possibJe sources of magmatic-hydrothermal fluid conuibutÎons to the Pb-Zn veins (Amaudov et al ., 1990).

The available data for the timiog of high-grade metamorphism eveot (36Ma, >600°C), eooliog (34Ma, 300°C) of the core complex aod voleaoie flows (30Ma) eonfirms the idea for the rapid exhumation during the extensional unroofing (Liati & Gebauer, 1999; Peycheva et al. , 2000). Petrological data on rapid AJpine exhumation lead to similar conclusion for the North-WeSlem Riia MI. (Chemeva & Amaudova, 1998).

References: Arkadakskiy, S. V., Boehm C, Hemao L, Chemeva Z & Staoeheva E. 2000. New U-Pb age

results from the Central Rhodope Mts, Bulgaria ABCD GEODE Workshop - Boro,'ets, Abstracts, 1, 5.

Arnaudov, V., Pavlova, M" Amov, 8., Baldzhieva, Ts 1974. Age and genesis ofpegmatites from south Bulgaria as detennined from data on the isotopic composition of lead in the feldspars. Mioeral. Geoesis, Sofia, 315-332 (io Bulgariao).

Aroaudov, V , Amov B, Cherneva Z, Aroaudova R, Pavlova M & Bartoitsky E. 1990. Petrological-geochemical and lead-îsotope evidence of Alpine metamorphîsm in the Rhodope crystalline complex. Geologica Balcal1lca, 20.5, 29-44.

Chemeva, Z. & Amaudova, R. 1998. Magmatic epidote in the Kalin granite pluton, North­Westem Riia Mt. Geochemislry. mineralogy anei petr%gy. Bulgariau Academy of sciences, 34, 59-72.

Ivanov, Z. 1989. Structure and tectonic evolution ofthe central pans ofthe Rhodope massif. II/ Gllide 10 eXCllrsiOI/ E-3, CBGA-XlV COl/gress, Sofia, BIIlg., 126.

Liati, A. & Gebauer. 0 . 1999. Constraining the prograde and retrograde P-T-t path of Eocene HP rocks by SHRlMP dating of different zircon domins: inferred rates of heating, burial. cooling and exhumation for central Rhodope, no.,hem Greece. Contrib. Mineral. Petrol. (135): 340-354 .

Peycheva, 1., Salnikova E, Kostitsin V, Ovtcharova M & Sarov, S 2000. Metagranites from the Madan-Oavidkovo dome, Central Rhodopes: U-Pb and Rb-Sr prOlolithe aod metamorphism datiog. ABCD GEODE Workshop - Borovets. Abstracts, 1,67.

PERMlA METARHYOLlTES ANO RE LATE O ORE OEPOSITS, C ENTRAL BOS ' IA

Ladislav Palinkas l, Sabina Strmic1, Vesna Garasic1, Ivan Jurkovie, Vladimir Maje~

I Faculty of Sciences, University of Zagreb, Horvatovac bb, Zagreb, Croatia 1 Faculty ofMining, Geology and Petroleum Engineering, Zagreb, Croatia J Croatian Academy of Sciences and Ans, Ante Kovatica 5, Zagreb, Croalia

76

Geology and ore deposits The Midd-Bosnian Schist Mountains (MBSM) are in the Central Dinarides at the edge of the Carbonate platfarm. The major rocks of the MBSM are pre-Devonian metamorphic rocks (KIAr age, 343±13 Ma, PALIN1<AS et al. , 1996). Fossiliferous Devonian carbonate rocks overlie this metamorphic complex. The main phase of volcanic activity occurred during Permian time (JURKOV1C, 1957) giving large masses of qual1z perphyries. These rocks have undergone a metamorphism of high pressure (10.5-14.5 kbar) being indicated in the presence of phengite (MNER & GARASIC, in press). So the most appropriate name for quartz porphyries Îs metarhyolites. QU3nz-porphyries and adjacent ore deposits are probably formed at a post-collisional phase of the Hercynian orogeny ar incipient, widespread rifting wilhi" Pangea a ) Vrt lasce type" pyrrhotite. subordinate are pyrite, chalcopyrite, sphalerite, and silver­bearing gale"a, quartz. Galeoa contains 0.139 wt .% Ag; b.) 8akovici type: pyrite, quartz and siderite. Stibnite, galena, tetrahedrite, chalcopyrite, banle, arsenopyrite, hematite and gypsum are accessories. The pyrite is gold bearing. The average content is 14.62 git Au. The 5J4S value in pyrite is +4.78 and +6.76%0; c.) Cerner"ica type: quanz (over 90"10), stibnite and sphalerite, less abundant is cinnabar. The 534$ in Sb2S3 +2.12 and +3.48 and in Zn +3.71%0; d.) Trosnik type: pyrite, Sb-tertahedrite, quartz and siderite. Tetrahedrite is gold and si lver bearing. The average Au content is 561g1t. The 53"S in tetrahedrite is +3.28 and +3 .73960; e.) Hrmza type' realgar and orpiment, quartz. 534S in AsS +0.99%0, in orpiment + 1.32%0; f.) Kresevo type: barite and Cu-Sb-Hg tetrahedrite; g) Mackara type: siderite and quartz. 03"S in tetrahedrites -10 22%0

Fluid inclusion study The objects of fluid inclusion (FIs) study were quartl, barite and hyalophane rrom Cememica, Kresevo, Rastelica, Berberusa, Hrmza, Bakovici and Busovaca. Aqueous FIs rrom Rastelica and Hrmza are highly sali ne CaCh- aCI-H,O Thtotal into liquid phase 150-345°C suggesis ore-forrning environmems, spatially related to quanz-porphyry volcanism. Aqueous-carbonic FIs, in Busovaca, Berberusa and Bakovici contain, beside CO2, olher volatiles. Micro Raman speclroSCOpy recognized in Busovaca, presence ofC02• H20, N2, and carbonates as daughter minerals (P ALI1\TJ<AS el al , 1996). Salinity is low to moderate. T h is between 270 -410°C. Complex assemblages of Fis, of both types are in Cemernica and Kresevo. Aqueous FIs in Cemernica are moderately saline NaCI-KCI-H20, and aqueous Fis from Kresevo are the same as FIs from Rastelica. Aqueous-carbonic Fis contain, beside CO2,

other volatiles. Observed T h is between 150-330°C.

References: Pali"kas L. A. (1990): Siderite-barite-polysulfide depesits and early continental rifting in

Dinarides. -Geol. Vjesnik, Zagreb Palinkas L. A. et al. ( 1996): On use of hyalophane for K-Ar dating in the Central Bosnian

Schist Mts. -Act a geologica Hungarica, Budapest lurkovic 1. (1957): The basic characteristics of the metallogenic regio" of the Mid Bosnian

Ore Mountains. _2th Geol. Congress of FNRJ, Sarajevo