Bor - Borska Reka, Tilva Rosh, Choka Dulkan, Tilva Mika

Serbia, Serbia

Main commodities: Cu Au
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The Bor Porphyry and High Sulphidation Cu-Au deposit is located in the Timok Mountains of eastern Serbia, approximately 150 km SE of the capital, Beograd (Belgrade).

Sub-cropping massive, high sulphidation mineralisation was discovered at Bor at the turn of the 20th century with mining commencing in 1903. Subsequent mining and exploration drilling has shown that the massive sulphide orebodies are spatially related to deeper porphyry style mineralisation, the Borska Reka deposit. The two styles are continuous, linked by a transitional stockwork zone. The length of the altered and mineralised structural zone exceeds 2000 m with a width of around 1000 m, while the mineralised zone, which dips at 50° to the west, has been drill tested to a depth of at least 1500 m below surface. Past production + current reserves of the high sulphidation Cu-Au zone is estimated to total 3 Mt Cu, 160 t Au and 600 t Ag from 200 Mt of ore with an average grade of 1.5% Cu and 0.8 g/t Au (Monthel et al., 2002).

The host sequence at Bor is dominated by porphyritic hornblende-biotite andesites, andesitic tuffs and minor dacites. These volcanic rocks are overlain by pelitic sediments, and are underlain by a series of Late Cretaceous conglomerates and sandstones, which are nowhere mineralised.

High sulphidation mineralisation is characterised by a series of massive, cigar-shaped, or pipe-like bodies, together with mineralisation in fracture zones and in volcanic breccias. The largest of the sulphide bodies is Tilva Rosh with other major bodies such as Choka Dulkan and Tilva Mika. Tilva Rosh, which had maximum plan dimensions of 650 x 300 m and extended vertically for as much as 800 m, comprised both massive and disseminated sulphide mineralisation. The massive sulphide orebody of Choka Dulkan has a strike of some 150 m, thickness of 60-70 m and a vertical extent of around 300 m.

The massive copper ore at Bor contains 3 to 6% Cu and comprises up to 70% (by volume) fine-grained pyrite, accompanied by up to 2.5 to 3.75 g/t Au (locally to 18 g/t Au) and 10 g/t Ag (Jankovic, 1982; Monthel et al., 2002). The principal copper minerals are chalcocite, covellite and enargite, with associated marcasite, chalcopyrite, tetrahedrite and sulvanite. Spectacularly bladed hypogene covellite is common in the massive sulphide ore. Traces of galena and sphalerite are present in the massive sulphides, although these minerals form a major component of the Choka Marin high-sulphidation body which lies to the north of Bor. Associated gangue minerals are significant amounts of silica, barite, ubiquitous anhydrite and native sulphur. Barite is more common in the upper sections of the system, while the predominant sulphate mineral in the lower levels is anhydrite. Native sulphur accompanies high-grade enargite and covellite veining in one of the orebodies. Very late gypsum veins are also common.

There is a suggestion of a sulphide mineralogy zonation within the massive ore to a pyrite-chalcopyrite-bornite (occasionally pyrrhotite) association in the lower levels, possibly indicating a change in sulphur activity. The massive ores grade laterally and at depth to disseminated mineralisation. A system of thin sub-parallel veins is developed beneath the large Tilva Rosh body although post-ore faulting has removed the lower sections of bodies such as Choka Dulkan. The disseminated zones also carry significant sulphide mineralisation (>0.6% Cu) and form part of the ore reserves.

Alteration is distinctive around the high-sulphidation deposits with a change at depth towards the porphyry style mineralisation. In the upper parts of the high-sulphidation system, silicification is the common alteration with vuggy silica developed close to the interpreted palaeosurface. Outward zoned advanced argillic alteration, characterised by in an inner envelope of kaolinisation and peripheral chlorite surrounds the orebodies, in places accompanied by pyrophyllite, diaspore and alunite, and locally with andalusite, zunyite, sericite and some corundum. Alunite is most abundant in the upper parts of the alteration. Kaolinite is commonly associated with the alunite (Karamata et al., 1983).

The porphyry style disseminated and stockwork mineralisation of Borska Reka is associated with dykes and minor intrusions of diorite which are restricted to its lower sections. The bulk of the mineralisation is hosted by altered andesite which has a distinct porphyritic texture. Alteration is characterised by silicification and illite-argillisation, accompanied by chlorite, alunite and carbonates, although alunite is widespread in parts of the deposit. The principal Cu sulphide is chalcopyrite with up to 6% (by volume) pyrite, and in the lower levels, molybdenite. These sulphides are accompanied by magnetite, minor pyrrhotite, enargite and bornite, and are overprinted in parts by chalcocite and covellite. This porphyry deposits contains around 600 Mt @ 0.6% Cu, 0.25 g/t Au.

The most recent source geological information used to prepare this summary was dated: 2005.    
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.

  References & Additional Information
   Selected References:
Ciobanu, C.L., Cook, N.J. and Stein, H.,  2002 - Regional setting and geochronology of the Late Cretaceous Banatitic Magmatic and Metallogenetic Belt: in    Mineralium Deposita   v.37, pp. 541-567.
Clark A H and Ullrich T D  2004 - 40Ar- 39Ar age data for andesitic magmatism and hydrothermal activity in the Timok Massif, eastern Serbia: implications for metallogenetic relationships in the Bor copper-gold subprovince: in    Mineralium Deposita   v39 pp 256-262
Heinrich C A, Neubauer F  2002 - Cu - Au - Pb - Zn - Ag metallogeny of the Alpine - Balkan - Carpathian - Dinaride geodynamic province: in    Mineralium Deposita   v37 pp 533-540
Herrington R, Jankovic S and Kozelj D  1998 - The Bor and Majdanpek copper-gold deposits in the context of the Bor Metallogenic Zone: in Porter, T.M. (Ed), 1998 Porphyry and Hydrothermal Copper and Gold Deposits - A Global Perspective PGC Publishing, Adelaide,    pp 185-194
Lips, A., Herrington, R., Stein, G., Kozelj, D., Popov, K. and Wijbrans, J  2004 - Refined tuning of porphyry copper formation in the Serbian and Bulgarian portions of the Cretaceous Carpatho-Balkan Belt: in    Econ. Geol.   v99 pp. 601-609
Zimmerman, A., Stein, H.J., Hannah, J.L., Kozelj, D., Bogdanov, K. and Berza, T.,  2008 - Tectonic configuration of the Apuseni-Banat-Timok-Srednogorie belt, Balkans-South Carpathians, constrained by high precision Re-Os molybdenite ages: in    Mineralium Deposita   v.43, pp. 1-21.

   References in PGC Publishing Books: Want any of our books ? Pricelist
Herrington R, Jankovic S, Kozelj D, 1998 - The Bor and Majdanpek copper-gold deposits in the context of the Bor Metallogenic Zone (Serbia, Yugoslavia),   in  Porter T M, (Ed.),  Porphyry and Hydrothermal Copper and Gold Deposits: A Global Perspective,    pp 185-194
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Armstong R, Kozelj D and Herrington R, 2005 - The Majdanpek Cu-Au Porphyry Deposit of Eastern Serbia: A Review,   in  Porter T M, (Ed),  Super Porphyry Copper and Gold Deposits: A Global Perspective,  v2  pp 453-466
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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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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