Morphology, Composition, and Ontogenesis of Platinum-Group Minerals in Chromitites of Zoned Clinopyroxenite-Dunite Massifs of the Middle Urals

摘要

We present results of analysis of the morphology and chemical composition of platinum-group minerals from chromite-platinum orebodies of zoned clinopyroxenite-dunite massifs in the Middle Urals (Nizhnii Tagil, Svetlyi Bor, Veresovyi Bor, and Kame-nushenskii). Study of more than 500 grains has given an insight into the sequence of formation of platinum-group minerals in chromitites of the studied massifs. Three assemblages of platinum-group minerals have been revealed: magmatic (Os-Ir-Ru intermetallic compounds, isoferroplatinum, ferroplatinum, sulfides of the isomorphous series erlichmanite-laurite and kashinite-bowieite, and thiospinels of the series cuproiridsite-cuprorhodsite-malanite); postmagmatic (with a predominance of tulameenite, tetraferroplatinum, and fenonickelplatinum, resulted from sapcntinization of dunites); and latest secondary (minerals with a predominance of PGE sulfides, arsenides, sulfoantimonides, sulfoarsenides, plumbides, and amalgams).