Accessory Minerals in the Chromitite Ores of Dzharlybutak Ore Group of Kempirsai Massif (Southern Urals, Kazakhstan): Clues for Ore Genesis

The paper provides results of a detailed mineralogical study some chromitite ores from two deposits in the Southern Urals Kazakhstan: Almaz-Zhemchuzhina and Geofizicheskoe-VII. It is revealed that main ore minerals are Cr-spinel with high Cr# (Cr/(Cr + Al) = 0.8–0.83), as well serpentine chlorite, replacing primary olivine. Chromium spinel grains contain mineral inclusions, which distributed rather unevenly. most common inclusions olivine (serpentine) amphibole; phlogopite, pyroxenes, base metal sulfides rare. Olivine chromite highest magnesium (Fo97–98), anomalously nickel (up to 1.8 wt.% NiO). closure exchange reactions between occurred temperature range 700–850 °C oxygen fugacity −1.04 … +2.8 ΔFMQ, likely corresponds upper mantle settings fore-arc basin. A few tens monomineral polymineral intergrowths platinum group (PGMs) were found aggregates. Notably, mainly represented by Ru, Os, Ir disulfides, while iridium prevails (with widespread native phases, sulfides, sulfoarsenides). PGM included often associated hydrous silicates: amphibole, less phlogopite or chlorite. Discussed possible genesis inclusions. As preliminary conclusion, we suggest solid-phase processes played significant role crystallization investigated ores.