Platinum-group minerals and tetraauricupride in ophiolitic rocks of Skyros island, Greece

Abstract

In the serpentinized ophiolitic rocks from Skyros island, two distinct assemblages of base metal sulphides (BMS) and platinum-group minerals (PGM) occur. The first (early) generation is associated with chromitites which are enriched in platinum-group elements (PGE). The highest values were recorded in samples from Achladones (Ru 1210, Ir 780, Os 630, Rh 228, Pt 208, Pd 22; all values in ppb). Mineral inclusions in chromite consist of Ni-Fe sulphides and Os-rich laurite, and crystallized at high sulphur fugacity (fS2) during chromite formation. The second (late) generation is closely associated with Au-rich, PGE-poor magnetite ores which host a complex assemblage of inclusions consisting mainly of graphite, Cu-Fe- and pure Cu sulphides, sperrylite and tetraauricupride. Their accompanying hydrous silicates are Cl-bearing. It is assumed that this mineral assemblage was deposited by hydrothermal processes during serpentinization. © 1992 Springer-Verlag