PLATINUM-GROUP MINERALS FROM THE OLKHOVAYA-1 PLACERS RELATED TO THE KARAGINSKY OPHIOLITE COMPLEX, KAMCHATSKIY MYS PENINSULA, RUSSIA

Mineral assemblages from the Olkhovaya-1 River placers, in Kamchatka, Far-Eastern Russia, provide genetic information on their evolution. The minerals are dominated by Os-Ir-Ru alloys (80%), consisting of all possible mineral species, and Pt-Fe alloys consisting of native platinum, Fe-rich platinum and isoferroplatinum. The following features of the mineral assemblage are characteristic of mineralization associated with an ophiolitic complex: (1) in the Os-Ru-Ir diagram, the compositions of the hexagonal alloy form a ruthenium trend; (2) there are two typical equilibrium magmatic parageneses of alloys: early osmium iridium, and later isoferroplatinum-ruthenium, which both are associated with laurite and the solid solution laurite-irarsite (Ru,Ir) (S,As)(2). The cooperite, sperrylite and Pd minerals formed at the postmagmatic stage. Tetraferroplatinum-tulameenite, replacing the Pt-Fe alloys, as well as the multicomponent compounds of Ru, Os, Ir, Rh, Pt with Fe replacing the Os-Ir-Ru alloys and PGE sulfides, result from serpentinization of PGM-bearing rocks. The PGM assemblage in the Ol'khovaya-1 River placers is related to the Karaginsky ophiolite complex of the Kamchatskiy Mys Peninsula.