Behavior of noble metals upon fractional crystallization of copper-rich sulfide melts

Abstract

Joint behavior of Pt, Pd, Au, As, Bi, Te, and Sn upon fractional crystallization was studied in a melt of cubanite composition with the following admixtures (mol %): Fe, 33.20; Cu, 16.55; S, 50.03; Pt, 0.03; Pd, 0.02; Au, 0.02; As, 0.02; Bi, 0.03; Te, 0.02; Sn, 0.08. The crystallized sample consisted of three zones: (I) a pyrrhotite solid solution POSS; (II) an isocubanite ICB; (III) a multiphase mixture. The behavior of admixtures was studied in the first and second zones. It was shown that pyrrhotite did not contain admixtures of noble metals and accessory elements, whereas Sn was dissolved in cubanite. Other admixtures occurred in the second zone as multiphase inclusions. PdBi_хTe_1–х, PtBiS_3–δ, CuPtBiS₃, Bi₂S_3–х, Au, Pt(As,S)₂, (Pt,Pd)S, (Pt,Pd)(Bi,Te)_2–x, and PdBi₂ were the most abundant phases.