Genetic aspect of Cu-Mi sulfide mineralization during komatiite and related magmatism

Three different genetic types of deposits have been analyzed to reveal simi larities and differences of Cu-Ni sulfide mineralization. Comparison is per formed by the example of the deposits related to the Archean komatiites of Western Australia, Phanerozoic (P-T) komatiites of Western Vietnam, and Pha nerozoic (P-T) komatiite-like melts of the Norilsk district of the Siberian Platform. Comparison is made according to a number of indications and para meters of hugh genetic importance such as: geodynamic and geologotectonic s etting, relation of the deposits to high-Mg melts, Ni/Cu propotions in ores and character of sulfide mineralization, facies of ore-bearing melts, spec ific conditions of deposition, etc. Taking into account literature and our own data, we suppose that the sulfide melt in the Archean komatiites is eff used nearly simultaneously with their lavas at a small thickness of the Ear th's crust, whereas the deposits in the Phanerozoic komatiite-like hypabyss al Norilsk ore-bearing intrusions are evidently dominated by sulfurization- metasomatic genesis. Unlike these, the Phanerozoic Ban Phuc deposit, relate d to a komatiite-basalt volcanoplutonic complex in northwestern Vietnam, ex hibits an intermediate variant of genesis: It includes the appearance of ma ssive veined ores at the magmatic stage of formation of this deposit, where as the streaky and vein-disseminated ores seemed to appear during sulfuriza tion - at fluid-magmatic and hydrothermal stages. The close genesis of the considered types of deposits of Pt-Cu-Ni ore formation Is mainly due to a d eep-seated source of sulfur.