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1-1: Porphyry Cu–Au and epithermal Au–Ag deposits in the southern Apuseni Mountains, Romania
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1–1: Porphyry Cu–Au and epithermal Au–Ag deposits in the southern Apuseni Mountains, Romania South Apuseni Mountains district: Lat. 46°03’ N, Long. 22°58’ E K. Kouzmanova*, P. Ivăşcanub, G. O’Connorc a
Isotope Geology and Mineral Resources, ETH, Sonneggstrasse 5, 8092 Zurich, Switzerland b Geological Institute of Romania, Caransebes Str.1, 78344 Bucharest, Romania c Gabriel Resources Ltd, Suite 1501, 110 Yonge St, Toronto, ON, M5C 1T4, Canada Received 19 November 2004, accepted 1 May 2005
Fig. 1. Geological map of the South Apuseni Mountains district showing distribution of porphyry Cu and spatially related epithermal Au–Ag deposits; modified from Bostinescu (1984).
Producing mining district: mining in the district has been active for almost 2,000 years and is documented from pre-Roman times Some of the main deposits are: Roşia Montană, Roşia Poieni, * corresponding author: e-mail [email protected] 0169-1368/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.oregeorev.2005.07.030
Barza–Musariu (Brad district), Săcărîmb, Deva and Certej (Fig. 1). Mining: Underground and open pits. Commodities: Au, Ag, Cu, Zn, Pb. Annual production: exact past and present production figures are impossible to establish. Resources: Roşia Montană epithermal Au–Ag deposit (Fig. 2): 400.4 Mt @ 1.3 g/t Au, 6 g/t Ag; total resources 16.1 Moz of Au and 73.3 Moz of Ag. Roşia Poieni porphyry Cu deposit: 431 Mt @ 0.55%Cu, 0.25 g/t Au. Bucium–Tarnita porphyry Cu deposit: 335 Mt @ 0.50%Cu, 0.36 g/t Au. Certej epithermal Au–Ag deposit: 61.1 Mt @ 1.79 g/t Au, 10 g/t Ag (3.46 Moz Au, 18.2 Moz Ag). Rodu– Frasin epithermal Au–Ag deposit: 35.2 Mt @ 1.12 g/t Au, 3 g/t Ag (1.22 Moz Au, 2.92 Moz Ag). Type: porphyry copper–gold and epithermal low- to intermediate-sulphidation Au–Ag±Te deposits. Morphology: Porphyry mineralization is hosted mainly by subvolcanic andesitic bodies and forms stockworks, disseminations and impregnations and sometimes occurs as breccia infill (Fig. 3). Epithermal mineralization is developed mainly as steeply dipping veins or hydrothermal breccia zones crosscutting basement rocks, andesitic lavas, subvolcanic intrusions and Cretaceous or Tertiary sediments. Minerals in epithermal veins occur in open-space filling and crustiform textures. Telescoping of porphyry and epithermal mineralization is common. Age of mineralization: porphyry mineralization is contemporaneous with associated Miocene magmatism (see below); epithermal mineralization post-dates the porphyry-type ore formation. Ore minerals: chalcopyrite, gold, electrum ± sphalerite, galena, tellurides in the epithermal deposits; bornite in the porphyry-type deposits. Alteration: potassic, phyllic to argillic in the porphyry copper deposits; propylitic, quartz–
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Fig. 2. E–W cross-section through the diatreme-hosted Roşia Montană Au–Ag deposit (from O’Connor et al., 2003). Mineralization occurs within an intermediate-sulphidation style epithermal mineralized system, hosted by dacitic intrusions and associated phreato-magmatic breccias.
adularia–illite to argillic in the epithermal deposits. Age of host rocks: Miocene, 14.7 to 7.4 Ma, based on K–Ar dating on whole rock (Roşu et al., 2004). Nature of host rocks: calc-alkaline andesites to dacites, mainly andesites, with subordinate occurrences of alkaline affinity. Existing stable isotope analyses (O, H, S, C; Alderton and Fallick, 2000), combined with recent LA–ICP–MS analyses of fluid inclusions from porphyry and epithermal systems in the southern Apuseni Mountains, support the concept of a dominant magmatic component in the hydrothermal fluids of both deposit types. References
Fig. 3. NE–SW cross-section through the Deva porphyry Cu–Au deposit, consisting of cylindrical 0.5 km diameter breccia-hosted subvolcanic stock. Mineralization consists of bornite–chalcopyrite–magnetite stringers and impregnations, producing ore grade up to 2%Cu.
Alderton, D.H.M., Fallick, A.E., 2000. The nature and genesis of gold–silver–tellurium mineralization in the Metaliferi Mountains of western Romania: Economic Geology 95, 495–515. Bostinescu, S., 1984. Porphyry copper systems in the South Apuseni Mountains, Romania. Annuaire de l'Institut de Géologie et Géophysique 64, 163–174. O’Connor, G.V., Minut, A., Leary, S.F., 2003. The geology and exploration of the Roşia Montană gold deposit, Roşia Montană, Transylvania, Romania. In: Eliopoulos, D.G. et al. (Eds.), Mineral Exploration and Sustainable Development. Millpress, Rotterdam 2, pp. 1213–1216. Roşu, E., Seghedi, I., Downes, H., Alderton, D.H.M., Szakacs, A., Pecskay, Z., Panaiotu, C., Panaiotu, C.E., Nedelcu, L. 2004. Extension-related Miocene calcalkaline magmatism in the Apuseni Mountains, Romania: Origin of magmas. Schweizerische Mineralogische und Petrographische Mitteilungen 84, 153–172.
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1–1: Porphyry Cu–Au and epithermal Au–Ag deposits in the southern Apuseni Mountains, Romania South Apuseni Mountains district: Lat. 46°03’ N, Long. 22°58’ E K. Kouzmanova*, P. Ivăşcanub, G. O’Connorc a
Isotope Geology and Mineral Resources, ETH, Sonneggstrasse 5, 8092 Zurich, Switzerland b Geological Institute of Romania, Caransebes Str.1, 78344 Bucharest, Romania c Gabriel Resources Ltd, Suite 1501, 110 Yonge St, Toronto, ON, M5C 1T4, Canada Received 19 November 2004, accepted 1 May 2005
Fig. 1. Geological map of the South Apuseni Mountains district showing distribution of porphyry Cu and spatially related epithermal Au–Ag deposits; modified from Bostinescu (1984).
Producing mining district: mining in the district has been active for almost 2,000 years and is documented from pre-Roman times Some of the main deposits are: Roşia Montană, Roşia Poieni, * corresponding author: e-mail [email protected] 0169-1368/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.oregeorev.2005.07.030
Barza–Musariu (Brad district), Săcărîmb, Deva and Certej (Fig. 1). Mining: Underground and open pits. Commodities: Au, Ag, Cu, Zn, Pb. Annual production: exact past and present production figures are impossible to establish. Resources: Roşia Montană epithermal Au–Ag deposit (Fig. 2): 400.4 Mt @ 1.3 g/t Au, 6 g/t Ag; total resources 16.1 Moz of Au and 73.3 Moz of Ag. Roşia Poieni porphyry Cu deposit: 431 Mt @ 0.55%Cu, 0.25 g/t Au. Bucium–Tarnita porphyry Cu deposit: 335 Mt @ 0.50%Cu, 0.36 g/t Au. Certej epithermal Au–Ag deposit: 61.1 Mt @ 1.79 g/t Au, 10 g/t Ag (3.46 Moz Au, 18.2 Moz Ag). Rodu– Frasin epithermal Au–Ag deposit: 35.2 Mt @ 1.12 g/t Au, 3 g/t Ag (1.22 Moz Au, 2.92 Moz Ag). Type: porphyry copper–gold and epithermal low- to intermediate-sulphidation Au–Ag±Te deposits. Morphology: Porphyry mineralization is hosted mainly by subvolcanic andesitic bodies and forms stockworks, disseminations and impregnations and sometimes occurs as breccia infill (Fig. 3). Epithermal mineralization is developed mainly as steeply dipping veins or hydrothermal breccia zones crosscutting basement rocks, andesitic lavas, subvolcanic intrusions and Cretaceous or Tertiary sediments. Minerals in epithermal veins occur in open-space filling and crustiform textures. Telescoping of porphyry and epithermal mineralization is common. Age of mineralization: porphyry mineralization is contemporaneous with associated Miocene magmatism (see below); epithermal mineralization post-dates the porphyry-type ore formation. Ore minerals: chalcopyrite, gold, electrum ± sphalerite, galena, tellurides in the epithermal deposits; bornite in the porphyry-type deposits. Alteration: potassic, phyllic to argillic in the porphyry copper deposits; propylitic, quartz–
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Fig. 2. E–W cross-section through the diatreme-hosted Roşia Montană Au–Ag deposit (from O’Connor et al., 2003). Mineralization occurs within an intermediate-sulphidation style epithermal mineralized system, hosted by dacitic intrusions and associated phreato-magmatic breccias.
adularia–illite to argillic in the epithermal deposits. Age of host rocks: Miocene, 14.7 to 7.4 Ma, based on K–Ar dating on whole rock (Roşu et al., 2004). Nature of host rocks: calc-alkaline andesites to dacites, mainly andesites, with subordinate occurrences of alkaline affinity. Existing stable isotope analyses (O, H, S, C; Alderton and Fallick, 2000), combined with recent LA–ICP–MS analyses of fluid inclusions from porphyry and epithermal systems in the southern Apuseni Mountains, support the concept of a dominant magmatic component in the hydrothermal fluids of both deposit types. References
Fig. 3. NE–SW cross-section through the Deva porphyry Cu–Au deposit, consisting of cylindrical 0.5 km diameter breccia-hosted subvolcanic stock. Mineralization consists of bornite–chalcopyrite–magnetite stringers and impregnations, producing ore grade up to 2%Cu.
Alderton, D.H.M., Fallick, A.E., 2000. The nature and genesis of gold–silver–tellurium mineralization in the Metaliferi Mountains of western Romania: Economic Geology 95, 495–515. Bostinescu, S., 1984. Porphyry copper systems in the South Apuseni Mountains, Romania. Annuaire de l'Institut de Géologie et Géophysique 64, 163–174. O’Connor, G.V., Minut, A., Leary, S.F., 2003. The geology and exploration of the Roşia Montană gold deposit, Roşia Montană, Transylvania, Romania. In: Eliopoulos, D.G. et al. (Eds.), Mineral Exploration and Sustainable Development. Millpress, Rotterdam 2, pp. 1213–1216. Roşu, E., Seghedi, I., Downes, H., Alderton, D.H.M., Szakacs, A., Pecskay, Z., Panaiotu, C., Panaiotu, C.E., Nedelcu, L. 2004. Extension-related Miocene calcalkaline magmatism in the Apuseni Mountains, Romania: Origin of magmas. Schweizerische Mineralogische und Petrographische Mitteilungen 84, 153–172.