Platinum group mineral (PGM) and Fe-Ni-As-S minerals in the Sartohay chromitite, Xinjiang (NW China): Implications for the mobility of Os, Ir, Sb, and As during hydrothermal processes

- Platinum group minerals were found in the Sartohay chromitites.
- Fe-Ni-As-S minerals occurring in magnetite surrounding Fe-rich chromite replaced chrome-spinel in the Sartohay chromitites.
- Enrichments of Os, Ir, Sb, and As reflect their mobility during hydrothermal process overprinting the Sartohay ophiolite mélange.

The Sartohay chromitite deposit, hosted in the Sartohay ophiolite mélange in western Junggar (Xinjiang province, NW China), contains irarsite, breithauptite, and Fe-Ni-As-S minerals. Petrographic observations indicate that the chrome-spinel was firstly altered to Fe-rich chromite at low-temperature with relatively lower Fe3 +/Fe2 + ratios (0.14-0.34), and such Fe-rich chromite was altered to magnetite in a relatively oxidizing environment. Afterwards, irarsite, breithauptite, and Fe-Ni-As-S minerals formed during hydrothermal processes. A systematic change from magnetite-pentlandite, pentlandite-heazlewoodite-maucherite, millerite-breithauptite, to millerite-godlevskite-irarsite-dominated assemblage in the Sartohay chromitites suggests a complex evolutionary path in the P-T-fS2-fO2 space. Enrichments of Os, Ir, Sb, and As in disseminated irarsite, breithauptite, and Fe-Ni-As-S minerals reflect the mobility of Os, Ir, Sb, and As during low-temperature hydrothermal processes overprinting the chromitites in the Sartohay ophiolitic mélange.