Platinum-group mineralization in chromitites of Kurtushibinsky ophiolite belt (the Western Sayan): new data

Yurichev А. N., Chernyshov A. I.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019. V. 148. N 5. P. 113-125

https://doi.org/10.30695/zrmo/2019.1485.06

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Language: Russian

Abstract

Small scattered grains of PGE minerals have been found in chromitites of Ergaksky and Kalninsky ultramafic massifs, which are extreme northeastern fragments of the Kurtushibinsky Ophiolite Belt of Western Sayan. For the first time, together with reviously known PGE minerals, there were found the Cu—Ru—Os solid solution, arsenic-bearing (As up to 3.6 wt %) laurite with minor Pt, Ni, and Co, PGE sulfides of MeS and Me₃S₄ types, sulfoarsenide with the high content of Rh (~12.7 wt %) in chromitites of the Ergaksky massif, and laurite and sulfoarsenides in chromitites of the Kalninsky massif. Compositions of PGE minerals indicate high temperature of the Ru—Os sulfide formation (~1200—1250 ºC) in both massifs, as well as high partial pressure of sulfur under the formation of chromitites and syngenetic PGE minerals in the Ergaksky massif. PGE mineral assemblages were formed in several stages. Os—Ir—Ru solid solutions and disulfides of the laurite—erlichmanite series (mainly fractionating ruthenium) formed earlier than Cu—Ru—Os solid solutions, sulfides (Ru,Fe)₃S₄, (Ru,Ni,Fe)S, and PGE sulfoarsenides, which crystallized under influence of reduced fluids as a result of remobilization and redeposition of PGE.

Key words: chromitites, PGE minerals, ophiolites, Western Sayan