Platinum group element (PGE) mineralisation and chromite geochemistry in the Berit ophiolite (Elbistan/Kahramanmaraş), SE Turkey

Abstract

The high-Al chromitite-bearing stratigraphic levels (Cr# ranges from 0.38 to 0.47) are located at the mantle/crust transition zone (MTZ) and in the cumulate dunites in the Berit ophiolite in SE Turkey. Iridium group elements-IPGE (Ir, Os and Ru) and related mineralisation were previously reported from ophiolitic high-Cr chromitites in the Berit–Elbistan area. Palladium group elements — PPGE (Pt, Pd and Rh) and associated mineralisation are predominantly found in the high-Al chromitites and they are presented in this study for the first time. Our results indicate that IPGE-enriched phases of the PGMs such as laurite are present in both the PPGE-enriched and the PPGE-poor chromitites in Berit.The high-Al chromitite chondrite normalised patterns in the Berit ophiolite show an enrichment of PPGE, with values of up to 1700ppb Pt and up to 4469ppb Pd. During their occurrence sulphur saturation is consistent with the production of minor quantities of base metal sulphides (BMS) which took place in the form of droplets enclosed in chromite, commonly with PPGE-enriched patterns. These PPGM assemblages include Pd–Pt-tellurides, sperrylite, platarsite, Pd-antimonide, Pd–Sb–As, and Pt–Pd–Cu–Au– alloys. The PPGE enrichment in the Berit ophiolite is unusual, and the presence of such occurrences is known only in a few other ophiolites worldwide.The geochemical evolution of the high Cr# ratios of the high-Cr chromitites indicates an origin due to high degrees of partial melting, whereas the high-Al chromitites indicate lower degrees of partial melting. Both high-degree and low-degree melts may have been fluxed through the upper mantle, either synchronously or possibly with a hiatus between the generation of different melts.