Abstract

South African komatiites apparently do not host Ni sulfide ores similar to those found associated with komatiites in Western Australia, Zimbabwe, or Canada. The present paper examines whether the lack of mineralization could be related to the greater age of the South African komatiites, relative to most mineralized komatiites elsewhere. Many younger komatiites formed at shallower mantle levels than older komatiites. Therefore, they were potentially less S undersaturated during eruption and may have required less contamination to achieve S supersaturation. Further, they could possibly interact with more evolved and/or S-rich crust during eruption and/or intrusion. Alternatively, the age of komatiites may have little importance in controlling their mineralization potential. The lack of sulfide ores in the South African komatiites could then be related to (i) the relatively small size of the greenstone belts, (ii) the absence of lava channels in which sulfide ores tend to be concentrated, or (iii) the lack of a S-rich contaminant necessary to trigger S supersaturation in the lavas.

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