Ore Mineralization in Ultramafic and Metasomatic Rocks of the Ospin-Kitoi Massif, Eastern Sayan

摘要

In the Ospin-Kitoi ultramafic massif of the Eastern Sayan, accessory and ore Cr-spinel are mainly represented by alumochromite and chromite. Copper-nickel mineralization hosted in serpentinized ultramafic rocks occurs as separate grains of pentlandite and pyrrhotite, as well as assemblages of (i) hexagonal pyrrhotite + pentlandite + chalcopyrite and (ii) monoclinal pyrrhotite + pentlandite + chalcopyrite. Copper mineralization in rodingite is presented by bornite, chalcopyrite, and covellite. Talc-breunnerite-quartz and muscovite-breunnerite-quartz listvenite contains abundant sulfide and sulfoarsenide mineralization: pyrite, gersdorffite, sphalerite, Ag-Bi and Bi-galena, millerite, and kuestelite. Noble metal mineralization is represented by Ru-Ir-Os alloy, sulfides, and sulfoarsenides of these metals, Au-Cu-Ag alloys in chromitite, laurite intergrowth, an unnamed mineral with a composition of Cu3Pt, orcelite in carbonized serpentinite, and sperrylite and electrum in serpentinite. Sulfide mineralization formed at the late magmatic stage of the origination of intrusion and due to fluid-metamorphic and retrograde metasomatism of primary rocks.