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Radka |
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Bulgaria |
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Cu Au Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Radka intermediate sulphidation epithermal copper sulphide vein/replacement complex is located in the Panagyurishte district of the Srednogorie Zone of central Bulgaria, some 90 km SE of Sofia.
(#Location: 42° 22' 10"N, 24° 16' 44"E)
The geology of the district comprises Proterozoic gniesses and Palaeozoic granites of the Rhodope Massif and late Cretaceous volcano-plutonic complex of calc-alkaline to sub-alkaline affinities comprising extrusive andesitic and dacitic volcanics and pyroclastics. Locally within the district, Late Cretaceous flysch sediments cover parts of the sequence, while small outcrops of Palaeogene and Neogene molasse are also mapped.
The ore deposits are developed within WNW striking fault zones and are hosted by dacitic lavas, tuffs and tuff breccias and crosscutting rhyodacitic dykes of Late Cretaceous age and comprises a number of steeply dipping massive sulphide lenses surrounded by haloes of stringer and disseminated sulphides. These represent the two main ore types:
• Massive sulphides, with as much as 85 to 90% of sulphides which form lenticular or stock-like bodies, locally with highly variable morphology. The high permeability of the dacitic volcanic breccia and tuffs render them the most favorable lithologies for metasomatic replacement and hydrothermal precipitation, with fluid access controlled by faulting. The principal minerals in the massive sulphides are pyrite, chalcopyrite, bornite, tennantite, enargite, sphalerite, galena and chalcocite with subordinate Ge, Ga, In, Sn, Bi and Te bearing minerals. Late anhydrite is also common. The ore paragenesis comprises: i). early pyrite-quartz, ii). chalcopyrite-pyrite, iii). enargite-pyrite, iv). bornite-tennantite, v). sphalerite-galena, vi). late quartz-pyrite, vii). pyrite-marcasite, and viii). anhydrite-gypsum. Alteration is structurally controlled by faulting but generally comprises the following zonation outwards from ore of quartz-white mica → quartz-chlorite-white mica → propylitic assemblages.
• Veins, veinlets or dissemination of pyrite, chalcopyrite and quartz peripheral to the massive bodies.
A feature of the Radka mineralisation are polymictic breccia that has undergone quartz-white mica alteration and contain clasts of massive fine-grained to colloform pyrite (Bogdanov et al., 1970). The pyrite of these clasts is from the massive pyrite formed during the first stage of Fe (±As, Cu) mineralisation. The clasts are polymictic comprising dacite, dacitic tuffs and massive pyrite, and are subrounded to rounded, and rarely angular. The matrix is extremely altered to quartz-white mica ±argillic minerals and includes silt- and sand-sized clastic grains. These breccias occur as dykes that cross-cut the massive dacite host rock, but also the massive sulphide bodies. These macro- and microbreccia dykes are interpreted to indicate a process of fluidisation of
rock and ore fragments in upward-escaping fluid channelways that occurred after the deposition of the first mineralised assemblage (Kouzmanov et al., 2004).
The Bulgarian National Geologic Fund estimated the following (Mundoro Capital Inc. website, 2020).
Total production between 1928 and 1993 when the mine closed was:
6.39 Mt @ 1.06% Cu, 3 g/t Au and by-product pyrite.
The deposit was estimated to have remaining resources under the Bulgarian classification system of:
2.02 Mt @ 0.6% Cu, 0.57 g/t Au (category 221), plus 0.27 Mt @ 0.6% Cu, 0.53 g/t Au (category 222).
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2004.
Record last updated: 24/9/2020
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.
Radka
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Selected References:
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Bogdanov, K. and Popova, K., 2003 - Cu-Au Epithermal Systems in the Southern Part of the Panaguyrishte Ore Region, Bulgaria: in Bogdanov, K. and Strashimirov, S., (Eds.), 2003 Cretaceous Porphyry-Epithermal Systems of the Srednogorie Zone, Bulgaria Society of Economic Geologists, Guidebook Series, v.36, pp. 91-114.
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Kouzmanov K, Bailly L, Ramboz C, Rouer O, Beny J-M 2002 - Morphology, origin and infrared microthermometry of fluid inclusions in pyrite from the Radka Epithermal Copper deposit, Srednogorie zone, Bulgaria: in Mineralium Deposita v37 pp 599-613
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Kouzmanov, K., Ramboz, C., Bailly, L. and Bogdanov, K., 2004 - Genesis of high-sulfidation vinciennite-bearing Cu-As-Sn (-Au) assemblage from the Radka epithermal copper deposit, Bulgaria: evidence from mineralogy and infrared microthermometry of enargite: in The Canadian Mineralogist v.42, pp. 1501-1521.
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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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