Anomalous PGE concentrations in ophiolitic chromites and Cu ores associated with basic and ultrabasic rocks of the Polar Urals, Russia
Abstract
We studied ophiolitic Cr-ores at the Centralnoye I deposit and Cu ores at the Ozernoye deposit, associated with basic and ultrabasic rocks of the Keshorsk complex. Anomalous IPGE values (average 126 ppb) and a strong negative slope of mantle-normalized PGE patterns in chromites indicate the predominance of Ru-(Os)-Rh-Ir-bearing phases among the platinum group minerals (PGM) assemblage that is typical of mantle-hosted ophiolitic chromite ores. Low Pt values in chromites and increased Pt values in host dunites could reflect the presence of cumulus PGM grains. The studied Cu-ores of the Ozernoje deposit contain 0.14-0.63 wt.% Cu and 0.05-0.76 g/t ZPGE. Mineral paragenesis includes magnetite, chalcopyrite, cubanite, pyrrhotite and we also identified Pd, Pd-Te, Te-Ni and Ag-Te phases.