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Biely Vrch |
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Slovak Republic |
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Au
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Super Porphyry Cu and Au
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The Biely Vrch porphyry gold deposit is located near Detva, ~120 km NNE of Budapest in the Northern Carpathian Mountains in the Banskobystricky kraj region of the Slovak Republic.
The Carpathian Mountains lie within the upper arm of the reverse 'S' shaped, Mesozoic to Recent, oroclinal Carpathian-Balkan orogen. This orogen, which extends westerly through Bulgarian in the south, northwards through Serbia and Romania, and west again in Hungary and Slovakia, is part of the larger intracontinental Alpine-Tethyan-Himalayan orogenic system that extends from North Africa to southeast Asia. This larger orogenic system is the result of convergence of the African, Arabian and Indian plates and their collision with Eurasia, mainly from the Cretaceous to the present. Arc magmatism was initially driven by subduction of the intervening Neotethys Ocean in Mesozoic to Tertiary times but terminated at the time of collision in the Oligocene and was subsequently heavily overprinted by major, complex collision-related deformations and magmatism, including formation of the Carpathian-Balkan orocline.
The Carpathian Mountains and coincident magmatic arc (including the Central Slovakian Volcanic Field) lies to the south of a major arcuate, south dipping thrust zone and an intervening oceanic suture on the northern arm of the Carpathian-Balkan orogen/orocline. These magmatic rocks are overlain to the south by the Miocene to recent sedimentary rocks of the Pannonian Basin. This latter basin is floored by the Adriatic-Pannonian microcontinent. The northeastward incursion of this microcontinent, ahead of Africa, during collision and after, generated the prominent upper curvature of the orocline.
The Biely Vrch deposit lies on the northern extremity of the core of the Neogene Javorie andesite stratovolcano that is situated in the northeastern part of the Central Slovakian Volcanic Field. Several small occurrences of porphyry gold mineralisation are associated with the Krá'ová and Kalinka intrusive complexes within the stratovolcano, although to date Biely Vrch is the only one that has been shown to be of economic significance (Hanes et al., 2010).
The centre of the deposit is situated above a 300 x 400 m Mid Miocene diorite to monzodiorite porphyry stock emplaced in andesitic volcanic rocks. Post-mineralisation andesites and epiclastic breccias of the Javorie Formation are found to the south and east of the deposit. Palaeovolcanic reconstruction of the stratovolcano indicated intrusion of the porphyry stock at a depth of ~500 m (Konečný et al., 1998).
The porphyry stock and countryrock andesite and epiclastic breccias have been extensively altered (Konecný et al., 2010). The dominant alteration is intermediate argillic typified by an assemblage of illite-smectite, illite, chlorite and pyrite which variably overprints earlier high-temperature K silicate (K feldspar, biotite and magnetite) and Ca-Na silicate (intermediate to basic plagioclase, actinolite) alteration that are preserved deeper in the system. The vertical extent of high-temperature alteration zones is very limited, which is consistent with a the estimated shallow emplacement of the host intrusion.
The peripheries of the system are marked by a propylitic assemblage of illite-smectite, chlorite- smectite, chlorite and pyrite. An advanced argillic alteration assemblage of kaolinite, dickite, pyrophyllite, Al-phosphate-sulphate minerals and vuggy quartz represents the youngest stage of alteration.
The alteration is accompanied by several generations of hydrothermal-explosive breccias and veinlets (Koděra et al., 2010), including the earliest amphibole-pyroxene-apatite and biotite-magnetite veinlets that are associated with Ca-Na silicate and K silicate alteration respectively, as well as several generations of extensive quartz veinlets including A-type and later banded quartz. The economic Au mineralization is associated with a stockwork of quartz veinlets that persist to a depth from near surface to ~750 m, and occur, in altered rocks with clays, chlorite and K feldspar; sometimes attached to sulphides or Fe-Ti minerals (Koděra et al., 2010). Rare sulphide veinlets containing pyrite, chalcopyrite ±magnetite, marcasite, galena, sphalerite, mainly accompanied by chlorite and illite-smectite, are related to the intermediate argillic alteration phase. Late carbonate-zeolite veinlets are also relatively common. Veinlets with kaolinite, pyrophyllite and aluminum phosphate-sulphate minerals accompany the zones of advanced argillic alteration.
Ag, Cu, Pb and Zn values are elevated but are neither economic nor at levels which may affect gold extraction or be possible environmental pollutants.
Published resource estimates to a depth of >450 m, is 42 Mt @ 0.8 g/t Au (Fletcher and Bennett, 2010).
The most recent source geological information used to prepare this decription was dated: 2015.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Bacik, P., Kodera, P., Uher, P., Ozdin, D. and Janosik, M., 2015 - Chlorine-enriched tourmalines in hydrothermally altered diorite porphyry from the Biely Vrch porphyry gold deposit (Slovakia): in The Canadian Mineralogist v.53, pp. 673-691.
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Kodera, P., Kozak, J., Brcekova, J., Chovan, M., Lexa, J., Janosik, M., Biron, A., Uhlik, P. and Bakos, F., 2018 - Distribution and composition of gold in porphyry gold systems: example from the Biely Vrch deposit, Slovakia: in Mineralium Deposita v.53, pp. 1193-1212.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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