Problem of Nickel Source of Sulfide Deposits on the Siberian Platform

Nickel behavior in derivatives of tholeiite-basalt, picritoid and subalkaline basaltic melts is considered. A regular increase in nickel content in rocks has been followed with an increase in their Mg/(Fe + Mg) ratio. Genetic types of rocks, which differ in Ni content, have been recognized in the region of high-Mg traps. In the olivines of ore-free traps Ni content increases as the mineral Fe/(Fe + Mg) ratio decreases. When sulfur appears in magmatic melt, the system becomes destabilized to result in nonequilibrium state of the system, which is manifest in wide variations of olivine composition within one horizon of rocks or a spectrum. Taxitization of picrite gabbro-dolerites of the Norilsk intrusions is followed by depletion of olivine in Fe and Ni up to sterile forsterite. Ni-poor olivines of high-Mg rock are typical of near-root parts of ore-bearing massifs. The source of sulfide nickel is supposed to be silicate and its extraction by magmatogenic S-bearing fluids led to formation of sulfide liquid. For prospecting large nickel deposits derivatives of picritoid melts are more promising than those of tholeiitebasalts.