Experimental modeling of noble and chalcophile elements fractionation during solidification of cu-fe-ni-s melt

Abstract

We carried out a directed crystallization of a melt of the following composition (in mol. %): Fe 31.79, Cu 15.94, Ni 1.70, S 50.20, Sn 0.05, As 0.04, Pt, Pd, Rh, Ru, Ag, Au, Se, Te, Bi, and Sb by 0.03. The obtained cylindrical sample consisted of monosulfide solid solution (mss), nonstoichometric isocubanite (icb*), and three modifications of intermediate solid solution (iss1, iss2, iss3) crystallized from the melt. The simultaneous formation of two types of liquids separated during cooling of the parent sulfide melt was revealed. In the first, concentrations of noble metals associated with Bi, Sb, and Te were found. The second is related to Cu and was found to contain a large amount of S in addition to Bi and Sb. We established the main types of inclusions formed during fractional crystallization of Pt-bearing sulfide melt. It was shown that noble metals are concentrated in inclusions in the form of RuS2, PdTe2, (Pt,Pd)Te2, PtRhAsS, and Ag2Se, doped with Ag, Cu, and Pd, in mss and in the form of PtAs2; Au-doped with Ag, Cu, and Pd; Ag2Te; and Pd(Bi,Sb)xTe1−x in icb* and iss. As solid solutions in the base metal sulfides, Rh is present in mss, Sn in iss.