Metal-Sulfide Liquation Of Ore-Forming Melt In The Fe–Fe(NiCu)S–C System And Its Role In The Genesis Of Magmatic Sulfide Deposits In The Norilsky Region (By Experimental And Geological Data)

Abstract

The results of an experimental study of the melting of a graphite-saturated Fe–Fe(CuNi)S–C system at 0.5 GPa and 1150–1250°С with the addition of impurity elements Ag, Au, Re, Pt, Pd, and Rh are presented. The quenched sulfide melt forms the matrix of the sample, at 1150–1200°С it is represented by the FeNiS pyrrhotite phase (Mss) with inclusions of the FeCuS phase (Iss) anomalously enriched in Cu. At 1250°С, the sulfide melt is quenched in the form of a homogeneous pyrrhotite Ms phase of the Fe(CuNi)S composition. The change in the Ms composition of the quenched sulfide melt by the two-phase Mss + Iss association is considered as evidence of the existence of supra-liquidus Mss and Iss stratification of the sulfide Fe–Ni–Cu melt in the range of 1150–1250°С. As a result of fractionation of elements between immiscible Fe-sulfide (Ms) and Fe-metal (Mc) melts, Fe, Ni, Pt, Re, Au are predominantly concentrated in the metal melt, while Cu, Ag are concentrated in the sulfide melt. The role of the supra-liquidus Mss–Iss liquation in the genesis of sulfide mineralization of the deposits of the Talnakh ore cluster, including pyrrhotite-chalcopyrite "drops" in picritic gabbro-dolerites, as well as pyrrhotite and chalcopyrite types of ores of zonal sulfide deposits, is discussed. The role of Ms and Mc separation of the Fe-sulfide melt during carbon contamination in the Cu–Pd specialization of magmatic sulfide deposits of the Norilsk region is considered.