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Diversity of Epithermal Gold Ore Formation Events in SE Europe: a Record of a Protracted 60 M.Y.-Long Geodynamic and Metallogenic Evolution of the Tethyan Arc

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Diversity of Epithermal Gold Ore Formation Events in SE Europe: a Record of a Protracted 60 M.Y.-Long Geodynamic and Metallogenic Evolution of the Tethyan Arc Diversity of epithermal gold ore formation events in SE Europe: a record of a protracted 60 m.y.-long geodynamic and metallogenic evolution of the Tethyan arc Robert Moritz, Istvan Marton, Isabelle Chambefort, Cécile Noverraz University of Geneva, Switzerland Peter Marchev, Rumen Petrunov Bulgarian Academy of Sciences, Sofia, Bulgaria Richard Spikings & University of Geneva, Switzerland Nikolay Bonev St Kliment Ohridski Sofia University, Bulgaria Two major metallogenic zones in Bulgaria Late Cretaceous Banat- Timok-Srednogorie Zone ~95% of Bulgarian Cu and Au has been Carpathians produced in Panagyurishte district ( Cu porphyries and epithermal): PanagyurishtePlateforme Chelopech mine: one of the major mineralmoesienne district European gold deposits (31 Mt - 3.5 g/t Au - 1.39% Cu). Srednogorie Tertiary Rhodope Massif Rhodopes Major recent gold discoveries: Krumovgrad district Ada Tepe prospect (6.15 Mt - 4.6 g/t Au). After Popov (1996) Geology and ore deposits of the Panagyurishte district U-Pb ages of magmatic & ore forming events in the Panagyurishte district 92.1± 0.3 Ma & 91.84 ± 0.3 Ma 91.45 ± 0.15 Ma 91.3 ± 0.3 Ma • Progressive age decrease from north to south of magmatic and ore forming 90.36 ± 0.48 Ma 89.61 ± 0.26 Ma Medet events. • Attributed to slab retreat, slab roll-back. 90.06 ± 0.22 Ma • Roughly coeval porphyry-Cu and high- sulfidation epithermal ore formation in a 86.62 ± 0.11 Ma & given locality. 86.11 ± 0.23 Ma 85.66 ± 0.15 Ma 84.6 ± 0.3 Ma & 82.16 ± 0.1 Ma Capitan Dimitrievo 78.54 ± 0.13 Ma Data summarized in Von Quadt, Moritz, Peytcheva & Heinrich (2005) Southern Panagyurishte mineral district Vlaykov Vruh Elshitsa Porphyry-Cu deposit Epithermal Cu-Au deposit SE NW ~ 500 m ~ 1000 m Chelopech: paragegenetic sequence IIb: Tennantite-Bornite IIa: Enargite-Luzonite Chalcopyrite-Gold I: Massive banded pyrite Advanced argillic alteration Pyro- Typical of high-sulfidation phyllite 200 μm Zunyite Diaspore Alunite Py III: Sphalerite- Galena-Pyrite Vuggy silica 200 μm Dickite/Kaolinite -Baryte 0.3 mm Replaced oolith 1 mm Replaced accretionary lapilli Alpine tectonic overprint at Chelopech (Chambefort & Moritz, 2006) Post-ore formation tectonic overprint at the Chelopech high-sulfidation deposit 1st post-ore tectonic event: Folding, 2nd tectonic overprint: WNW-oriented axial plane Thrusting, NE-oriented plane Campanian- Maastrichtian flysch C H E L O P E C 91.45± 0.15 Ma H Chambefort and Moritz (2006) Exceptional preservation of the Late Cretaceous epithermal deposit attributed to: - Turonian to Maastrichtian sedimentary rock cover, & - Tertiary (?) NE-oriented thrusting (linked to recent dextral strike-slip tectonics?). Same metal source in epithermal Cu-Au & porphyry-Cu deposits from the Panagyurishte district: Pb isotope data from sulfides Data sources - Chelopech: Moritz (unpublished); Elatsite: Von Quadt et al. (2002); Krassen-Radka-Elshitsa-Vlaykov Vruh: Kouzmanov et al. (submitted) & Amov (1986). Isotopic composition of different barite generations at the Chelopech high-sulfidation deposit: main ore stage Enargite Main gold stage Early barite Intermediate barite Early stage pyrite 1cm 2 cm Tennantite-Pyrite S isotope thermometry= 240-250°C S isotope thermometry= 218-222°C Th fluid inclusions enargite = 200-243°C S isotope thermometry, late Pb-Zn-Ba stage (post-gold): 226°C Early barite 26 (enargite, 250°C) 24 Intermediate barite (tennantite, 220°C) S ‰ (PDB) S ‰ 22 34 δ Oxygen isotopic compositions: 20 Andesitic volcanic vapour Predominantly magmatic origin (Giggenbach, 1992) 18 Primary magmatic H2O (Taylor, 1979) Sulfur isotopic compositions: Magmatic origin 4 5 6 7 8 9 18 δ Ofluid ‰ (V-SMOW) Sr isotopes: ore fluid-basement rock interactions in the epithermal ore deposits from the Panagyurishte district Northern Panagyurishte: (Moritz et al., 2001; Chelopech HS deposit Barite Jacquat, 2003) Southern Panagyurishte: (Kouzmanov et al., 2001) Elshitsa & Radka Sulfate, calcite HS deposits Cretaceous intrusions Cret. volcanic rocks Paleozoic granites Metamorphic 0.733 basement Cretaceous seawater Cretaceous marls 0.704 0.705 0.706 0.707 0.708 0.709 0.715 0.716 87Sr / 86Sr Whole-rock data corrected for 80 Ma & 90 Ma in the Southern & the Northern Panagyurishte district, respectively. Fluid inclusion salinities in HS epithermal Cu-Au deposits from the Panagyurishte district (fragmentary data) Elshitsa Radka Chelopech 15 -10 Gold stage -8 Enargite ? -6 10 Quartz Co-rich -4 pyrite Quartz 5 -2 Enargite Barite Quartz Barite wt. % NaCl equivalent wt. % NaCl Ice melting temperature (°C) 0 0 Quartz- Barite Enargite chalcopyrite substage 1st substage 3rd Late substage (uncertain Fe-S timing of Pb-Zn-S Si-Fe stage inclusions) stage stage 2nd Cu-As-S stage Time Radka & Elshitsa data: Kouzmanov et al. (2000, 2002, 2004) & Kouzmanov (2001). Chelopech data: Moritz et al. (unpublished). High sulfidation - porphyry relationship Alteration Brine-vapor separation (high P) After Arribas (1995), Shinohara & Hedenquist (1997) , Fournier (1999) & Heinrich et al. (1999) Two major metallogenic zones in Bulgaria Late Cretaceous Banat- Timok-Srednogorie Zone ~95% of Bulgarian Cu and Au has been Carpathians produced in Panagyurishte district ( Cu porphyries and epithermal): PanagyurishtePlateforme Chelopech mine: one of the major mineralmoesienne district European gold deposits (31 Mt - 3.5 g/t Au - 1.39% Cu). Srednogorie Tertiary Rhodope Massif Rhodopes Major recent gold discoveries: Krumovgrad district Ada Tepe prospect (6.15 Mt - 4.6 g/t Au). After Popov (1996) Eastern Rhodopes: Regional tectonic control 9 Since the Cretaceous the Aegean Region experienced series of continental collision events, followed by syn- and post-orogenic extension in back arc region. 9 Tertiary extension: dome complex formation, fast uplift, followed by volcanic activity. 9 One of the most active, present day continental extensional setting in the world: rapid stretching of upper crust and exhumation of lower crust. 9 Similarities with Basin and Range Province: extensional back-arc tectonic setting considered to be the first order Marton et al. (2007) control for Carlin gold province Tertiary epithermal prospects in Rhodopes Spahievo: 31-32 Ma Volcanic-hosted base metal ± gold ± silver epithermal deposits (40Ar/39Ar ages, Laki Stremtsi: 37.5 Ma Madjarovo Singer & Marchev, 2000; 31-32 Ma Marchev & Singer, 2002). Madan Rosino: 36 Ma Volcanic-hosted gold-copper Ada Tepe: 35 Ma epithermal deposits (K-Ar ages, Pècskay et al., 2003). Sedimentary rock-hosted low sulfidation epithermal gold Perama-Sapes deposits (40Ar/39Ar ages, 28-32 Ma (K-Ar) Marchev et al., 2004; Metamorphic-hosted Pb-Zn replacement & vein deposits Spikings, 2007, pers. comm.). (29-31 Ma) Unrelated to and older than local magmatism. Associated with metamorphic core complexes. Origin of ore-forming fluids: still a matter of debate. Tertiary epithermal prospects in Rhodopes Spahievo: 31-32 Ma Sedimentary rock-hosted, Laki Stremtsi: 37.5 Ma low sulfidation epithermal Madjarovo 31-32 Ma prospects: Madan Rosino: 36 Ma The 40Ar/39Ar age range (~35- Ada Tepe: 35 Ma 37.5 Ma) indicates that on a regional scale, this was a long- lasting metallogenic event (extensional tectonics). Perama-Sapes 28-32 Ma (K-Ar) Tertiary sedimentary rock-hosted low sulfidation epithermal prospects • Combined lithological and structural control on ore body geometry. • Massive, siliceous ore body formed at the hanging wall of detachment. • Steeply dipping veins in Tertiary breccia conglomerates. Tertiary sedimentary rock-hosted low sulfidation epithermal prospects The coincidence of feeder, reactive and permeable lithologies favored gold transport and precipitation over extended areas. • Some rock units acted as major pH buffers ==> minor impact on desulphidation of an H2S-bearing fluid. • Reaction with marbles, marls and grantic rocks: acid neutratlisation. •H2S-bearing fluid was maintained at near neutral pH conditions ==> transport of gold was optimized over9 Builds extended up secondary areas. permeability in the host rock Tertiary sedimentary rock-hosted low sulfidation epithermal prospects Precipitation mechanisms: de-sulphidation, boiling & mixing ==> various ore types. • Amphibolites & serpentinites, with Fe-bearing minerals: favourable for desulphidation of an H2S- bearing fluid: Pyrite replaces amphiboles along cleavages & fractures. • Sulphidation of Fe in host rocks favours precipitation of As-rich pyrite. Stremtsi Rosino Up to 6-8 wt% As in pyrite rims Tertiary sedimentary rock-hosted low sulfidation epithermal prospects Precipitation mechanisms: de-sulphidation, boiling & mixing ==> various ore types. Bladed 2 carbonate 1 0 -1 -2 C (‰ PDB) of dolomite 13 -3 Stremtsi δ -4 12 14 16 18 20 22 24 Eastern silicified zone: δ18O (‰ SMOW) of dolomite veins (drill core samples) Western Ba-Pb-Zn zone: Western Ba-Pb-Zn zone veins (drill core samples) (surface samples) Adularia 100 μm Tertiary sedimentary rock-hosted low sulfidation epithermal prospects Precipitation mechanisms: de-sulphidation, boiling & mixing ==> various ore types. 2 Dilution with time 1 Barite Dolomite 5 N 0 Fluid A -1 0 0 1 2 3 4 5 -2 Salinity (wt% NaCl) C (‰ PDB) of dolomite 13 -3 Fluid B δ Stremtsi -4 12 14 16 18 20 22 24 Eastern silicified zone: δ18O (‰ SMOW) of dolomite veins (drill core samples) Western Ba-Pb-Zn zone: Western Ba-Pb-Zn zone Barite ± sphalerite ± veins (drill core samples) (surface samples) galena δ34S values: same fluid on regional scale Sedefche Sulfur isotopic composition of pyrite Skalak from sedimentary rock-hosted, Rosino low sulfidation epithermal prospects, Surnak Eastern Rhodopes (Marton et al., 2006) Ada Tepe -20 -15 -10 -5 0 5 10 15 Stremtsi (Noverraz et al., 2007) S G G S G G G S -42-31-23 -15 -10 -5 0 5 10 15 20 25 32 34 Pyrite with organic matter G Galena δ S (‰ CDT) Hydrothermal pyrite S Sphalerite Barite Tertiary epithermal prospects in Rhodopes Spahievo: 31-32 Ma Sedimentary rock-hosted, Laki Stremtsi: 37.5 Ma low sulfidation epithermal Madjarovo prospects: 31-32 Ma Madan Rosino: 36 Ma A regional, long-lasting event, Ada Tepe: 35 Ma which has a similar spatial extension as the deposits of the Carlin-trends or detachment- related gold deposits in the Western U.S.A.
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