Textural and geochemical distinction between supergene and hypogene Cu sulfide phases at the Mammoth copper deposit, Queensland, Australia

Mammoth is a sediment-hosted, structurally controlled, Proterozoic Cu deposit located in the Mt Isa Inlier. Hypogene and supergene chalcocite are identified within the deposit and they are texturally and paragenetically distinct. Pyrite, chalcopyrite, bornite and chalcocite (both hypogene and supergene) were analyzed using Laser Ablation (LA) ICP-MS for trace element geochemistry. Supergene chalcocite is enriched in Bi (83 ppm) and depleted in both Ag (23 ppm) and As (7 ppm) compared to hypogene chalcocite (26 ppm Bi, 302 ppm Ag and 45 ppm As). Conclusions of this study are: 1) chalcocite is a component of the hypogene ore mineralogy; 2) meteoric oxidation processes produced supergene chalcocite; and 3) clear distinction as to the genesis of the chalcocite mineralisation is possible using mineralogical, textural and geochemical criteria.