Natural polycomponent solid solutions of the Ru–Os–Ir–Pt–Fe system from the eastern Witwatersrand (South Africa)

Abstract

This study presents compositional features of platinum-group element mineralization derived from the Late Archaean placers in the eastern part of the Witwatersrand basin. The significant presence of platinum-group minerals, formed by polycomponent solid-solution series in the system Ru–Os–Ir–Pt(±Fe), was determined using an electron microprobe analysis. Compositional data indicate that the source for polycomponent solid solutions of the Ru–Os–Ir–Pt–Fe system was the Archaean mantle of the Earth, slightly differentiated with respect to platinum-group elements.