Menshikovite Pd3Ni2As3 and associated minerals of sulphide ores within the Eastern flank of the Oktyabrsky deposit (Norilsk ore field)

Abstract

Significant amount of menshikovite (rare palladium and nickel arsenide) Pd3Ni2As3 was found on the Eastern flank of the Oktyabrsky deposit (Norilsk ore field), near the contact of solid and impregnation sulfide Co-Ni-Cu ores among magnetite-plagioclase-fassaite skarns. Sulfide material of both ores consists of chalcopyrite, pentlandite, pyrrhotite and cubanite aggregates, which are the products of subsolidus transformations of high-temperature solid solutions Iss3, Iss4 and subordinate Mss; with interpositions of later Se-galenite. Menshikovite in association with mertieite-II, silver-gold (fineness 756–706), golden-electrum (fineness 694–672), kotulskite, moncheite, rare altaite, hessite, naldrettite and melonite forms small (up to 30 microns) metasomatic growths on the contact of silicate matrix and magmatogenic sulfide aggregates. The average composition of menshikovite is close to theoretical data: (Pd2,98Ru0,03)3,01(Ni1,89Fe0,-08Co0,01)1,98 (As2,94Se0,04Bi0,02Sn0,01)3,01. Sperrylite metacrystals cut the borders of menshikovite accretions as well as other minerals of precious metals and contain “corroded” inclusions. This association of minerals of noble metals has arisen under the increased activity of As, Te, Sb, Bi and low activity of Sn in fluids. Menshikovite is typical for Pd-rich ores of the Oktyabrsky Deposit, while mayakite PdNiAs (another palladium and nickel arsenide) is relatively widely developed in ores of the Talnakh Deposit (Mayak mine and partly Komsomolsky mine) and the Norilsk-I. Perhaps, such a distribution of palladium-nickel arsenides is an element of mineral zonality of the Norilsk ore field.