Cu-Au minerals and transformed mineral phases in the oxidation zone of the Plavica ore deposit, eastern Macedonia

Abstract

Within this paper we present the latest mineralogical and chemical studies of particular mineralsand mineral phases from oxidation zone and partially from the primary sulphide mineralization within the Cu-Аu depositPlavica. Oxide zone in this ore deposit represents a system of so-called hats of secondary alunitized quartzitesintensively oxidized and represented by veinlet and net-like Fe-oxide and Fe-hydroxides. The major feature of thiszone is interesting gold concentration. The major part of confirmed gold within alunitized iron quartzites reachesconcentrations within the range of 1.80 up to 5.85 g/t Au. The gold is often present as native gold, mostly in Fehydroxidesand in some places as finely dispersed in pyrite. There its concentration varies from 0.56 g/t up to 0.60 g/tAu. The mineral composition of the oxidation zone is quite extensive (about 31 minerals) of which as principal withprevailing share up to 70% are quartz, alunite, kaolinite and sericite, as secondary minerals accounting up to 11% arepyrite, goethite, chalcocite, hematite, bornite, covellite, malachite and azurite, while as rare mineral phases with shareunder 5% are chalcopyrite, tetrahedrite, tennantite, enargite, galena, sphalerite and others.