Intergrowths of platinum group minerals from the Miass placer zone (South Urals) and their primary sources

 V.V. Zaykov, I.Yu. Melekestseva, V.A.Kotlyarov, E.V. Zaykova , Yu.D. Kraynev 

UDК 549.27:549.3 (470.5)

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Twenty four platinum group minerals (PGMs) were found in the kialim and Maly Iremel gold placers of the Miass placer zone, South Urals. Rhodarsenite, bowieite, cuprorhodiste, and xingzhon-gite(?) were found in the Urals for the frst time. In the kialim placer, ruthenium is most abundant PGM, which hosts microinclusions of isoferroplatinum, ferroan platinum, laurite, cupriferous gold, tolovkite(?), heazlewoodite and unnamed mineral RhSbS. The osmium contains microinclusions of erlichmanite and laurite. The iridium grains include various sulfdes and arsenides of platinum group elements (PGEs) close in compositions to (Ir,Rh,Ni)S and (Ir,Os)3S2. The isoferroplatinum from the Maly Iremel placer hosts laurite, rhodarsenite, bowieite, miassite(?) and unnamed Pt sulfde and Pd antimonide close in compositions to PtS2 и Pd3Sb, respectively. Ruthenium is a host to isoferroplati-num, PGE sulfdes and arsenides and heazlewoodite. Osmium contains microinclusions of ferroan platinum; iridium is a host to hongshiite(?). Three types of PGM intergrowths were identifed in the Maly Iremel samples: 1) the intergrowths of platy crystals of ruthenium with isoferroplatinum and tulameenite(?); 2) the open-latticework intergrowths of platy crystals of ruthenium with interstitial aggregates of gold, isoferroplatinum, laurite and xingzhongite(?) and 3) the intergrowths of osmium and irarsite and iridarsenite, which are developed along cleavage of the osmium grains. The placer PGMs derived from adjacent ophiolitic ultramafc massifs (karabash, Talovka, Nurali).

Figures 12. Tables 2. References 38.

Key words: intergrowths, platinum group minerals, placers, South Urals.

МINERALOGY № 4 2016