The partition of Co, Ni, Cu, and Zn between sulfide and silicate liquids

Abstract

Partitioning coefficients (KMe) for Fe (1.2), Co (7), Ni (150), Cu (50), and Zn (0.5) were determined for conjugate iron sulfide/iron silicate liquids in the FeS-FeO-SiO2 system at 1,150 degrees C and 1 bar pressure. The partitioning is probably controlled by differences in crystal field energy splitting for these elements between sulfur- and oxygen-coordinated sites in the liquids. The coefficients agree with the geological observation that Fe, Ni, and Cu are the main metals of magmatic sulfide ores. Fe is concentrated because it is a major element in basic and ultramafic rocks and magmas; Ni and Cu are minor or trace elements in magmas but are concentrated in ores due to high KMe's. Co and Zn are trace elements in both magmas and ores, reflecting their low values of KMe's. Changes in Ni/Cu ratios in magmatic sulfide ores reflect Ni/Cu ratios in parent silicate magmas; high ratios are indicative of ultramafic magmas.