Occurrence of platinum-group minerals in chromities of the kluchevskoy ophiolite complex, central urals, Russia: preliminary results

摘要

The Kluchevskoy ophiolite complex (Central Urals, Russia) contains small chromitites bodies characterized by podiform-type morphology and composition. Platinum-group mineral (PGM) inclusions have been discovered, having the Ru-Os-Ir rich assemblage typical of Base Metal and S-poor chromitites from ophiolitic mantle, although showing a great variety of phases such as sulphides, sulpharsenides, arsenides, and alloys. Two distinct paragenetical assemblages have been recognised: i) primary magmatic PGM (laurite, erlichmanite, Os-Ir alloys, Ir-Rh sulphides, Ru-pentlandite, ruthenarsenite, irarsite), and ii) secondary PGM formed during post magmatic events (Ru-Os-Ir alloys). The magmatic assemblage is consistent with deposition of the PGM under a wide range of sulphur fugacity conditions. The secondary alloys formed by desulphuration of primary sulphides at low temperature.