Abstract
Plutonogenic ore-magmatic systems of the Noril’sk ore field are unique constituents of the P 2–T 1 trap formation in the East Siberian Platform. We consider the formation of ore-bearing intrusions, evolution of Cr-spinels in intrusive magmatites, possible mechanisms of formation of massive, disseminated, and impregnated magmatic sulfide ores, possible reasons for the abundance of sulfide melts, quasi-anhydrite isotopic composition of sulfur of sulfide ores, and products of interaction of sulfide melts with ore-hosting basites. The unique contents of PGE, Ag, and Au in ores (eutectic Iss–PbSss intergrowths, crystallization products of low-temperature Ni-Fe-Cu-Pb-S melts) have been estimated for the first time. We have established that pneumatolytic Ag-Au-Pt-Pd mineralization is intimately related to the fluid aureoles near magmatic sulfide bodies. Pneumatolytic PGM are subdivided into early (tetraferroplatinum with lamellae atokite, paolovite with lamellae of insizwaite-geversite and niggliite, etc.), middle (rustenburgite-atokite-zvyagintsevite, mayakite, stannopalladinite, polarite, plumbopalladinite, maslovite, tatiyanite-taimyrite, Pd-Pt-containing tetraauricupride, etc.), late (sobolevskite, froodite, hessite, michenerite, cabriite, minerals of Au-Ag series, etc.), and the latest (sperrylite). The direct, reverse, oscillation, and complex zoning of gold particles is much due to variations in the Te activity in the fluids. Pneumatolytic noble-metal minerals were produced at <490 ºC in strongly reducing conditions with extremely low S 2 fugacity. The Pb isotope composition evidences that all systems of the trap formation in the Noril’sk region had the same mantle source. The Pb isotope compositions of ore-bearing intrusions, magmatic sulfide ores, PbSss, and Pd-Pt intermetallides in the Noril’sk and Talnakh ore clusters differ significantly: Lead in the Talnakh cluster is more radiogenic. This evidences genetic relations between sulfide ores and particular intrusions as well as different intermediate magma chambers in the Noril’sk and Talnakh clusters, and a higher degree of contamination of mantle magmas in the Talnakh cluster, which might be the explanation of its giant area.
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