Heavy concentrate halos as prospecting guides for PGE mineralization

Absract Platinum-group minerals (PGM) in primary ores and placers are compared in order to substantiate prospecting guides for layered and differentiated intrusions containing sulfide Cu-Ni ores with platinum-group elements (PGE). It is shown that supergene placer mineral assemblages bear information on primary sources and their probable economic value. The mineralogical and geochemical data on the large Siberian intrusions that host Cu-Ni and low-sulfide PGM deposits (Noril’sk 1, Kingash, Chinei, and Yoko-Dovyren) are used to elaborate mineralogical prospecting guides based on the comparative study of PGM assemblages in primary ore, heavy concentrate halos, and hillside sediments. The mechanism of PGM redistribution under supergene conditions is exemplified in the Chinei deposit. The placer mineral assemblage with prevalence of Pt-Fe alloys, atokite-rustenburgite, sperrylite, and multicomponent Pd-Sn-Cu-Pb compounds can be used as a prospecting guide for Noril’sk-type primary PGM ore and related economic placers. The paolovite-sperrylite or sperrylite PGM assemblage in heavy concentrate halos indicates occurrence of Cu-Ni ore in the prospecting area. Sperrylite with isomorphic admixture of Ir and Os typical of the Kingash pluton could be a orospecting guide for Ni-bearing mafic-ultramafic intrusions.