Platinum-group elements in porphyry copper deposits: a reconnaissance study

Sulphide and flotation concentrates from 33 porphyry copper deposits have b een investigated for platinum-group elements (PGE), Au, Cu and platinum-gro up minerals (PGM). The major sulphides in the samples studied are chalcopyr ite and pyrite. Bornite is less frequent and molybdenite occurs in traces o nly. PGM (merenskyite, sperrylite and an unidentified Pd-Sb telluride) have been found as inclusions in chalcopyrite. Pd and Pt are present in concentrations above the analytical detection limi t (>8 ppb) in 70% respectively 30% of the deposits studied. The contents of Os, Ir, Ru and Rh are below detection limits in all samples. The analytica l results show that 7 deposits (six of island are and one of continental ma rgin setting) reveal relatively high Pd contents (130-1900 ppb) which are a ssociated with high Au contents (1-28 ppm). In five of them discrete PGM ca n be identified in accordance with elevated levels of Pd. Correlations of A u, Pd and Pt point towards a common origin. Even though the data base is relatively small, a trend is obvious, suggesti ng that Au-rich island are porphyry copper deposits might host more Pd and Pt than the continental margin type ones. Other aspects of intrusive rocks, such as geological age, chemical composition and magma type do not seem to influence PGE contents.