MSCC3 3rd MINERAL SCIENCES IN THE CARPATHIANS ...

Acta Mineralogica-Petrographica, Abstract Series 5, Szeged, 2006PRELIMINARY DATA CONCERNING THE Cu, Au, Ag DISTRIBUTION IN THE BOLCANAORE DEPOSIT, METALIFERI MTS., ROMANIAPOPESCU, GH. C. & CIOACA, M.Department of Mineralogy, University of Bucharest, 1, N. Bălcescu Bvd., RO-010041 Bucharest, RomaniaE-mail: mihaela2012@yahoo.comThe Bolcana ore deposit is one of the 14 porphyry copperstructures belonging to the Neogene metallogenesis of theMetaliferi Mts. The deposit is located on the south-westernborder of the Brad–Săcărâmb District, approximately 25 kmNE of Deva. It constitutes a part of the Troiţa–Măgura metallogeneticfield, with an exceptional concentration of metallicelements, presenting a copper-gold ring-zoned structure(POPESCU & NEACSU, 2005); the porphyry mineralizationoccupies a central position around which gold-silver andpolymetallic veins have developed. The copper-gold mineralizationhas a spatial and genetical relationship with a subvolcanicbody of Sarmatian age, formed of amphibolebearingandesites/microdiorites. The structure exhibits abrecciated structure with intensely hydrothermally alteredmicroveins and/or impregnations within the host rock. Themain metallic minerals are pyrite, chalcopyrite, magnetite andsubordinately, bornite, hematite, molybdenite, and nativegold. The most abundant minerals are chalcopyrite and magnetite;subordinate amounts of pyrite and bornite occur in thecentral part of the ore deposit. The mineralization is superimposedon a potassic alteration zone, whereas pyrite becomesdominant towards the upper and marginal part of the intenselyargillized mineralized body. The copper-gold mineralizationis cross-cut by epithermal polymetallic veinletsformed of sphalerite, galena, pyrite, chalcopyrite, tetrahedrite,bournonite, marcasite, etc., associated with carbonates andquartz-gold veinlets.The ore deposit has been investigated with mining works(at five levels) and drill works spanning over 1000 m indepth. Such works have made possible to outline four cylindricalbreccia columns within the Bolcana subvolcano(“breccia pipe”) which were richer in mineralization (the F17,F282-F13, F21-F4 and F3 zones). Distribution of Cu, Au andAg marks an increase of the metal content with depth, and adirect correlation between Au and Cu. Distribution mapsdrafted for each horizon and outlining the four mineralizedcolumns mentioned above, show Cu contents of over 2% andAu contents of over 0.3 g/t, as well as the overlapping of Cu,Au and Ag mineralization in most situations. There are caseswhere copper, gold and silver occur separately, suggestingtwo stages of mineral genesis: one with copper and anotherone with gold-silver.ReferencePOPESCU, GH & NEACSU, A. (2005): In: Abstracts, Vol.37, No. 97, GSA Annual Meeting SLC 2005, p. 516.www.sci.u-szeged.hu/asvanytan/acta.htm 95