Uvarovite from chromitites of the Agardag ultramafic massif (Tyva Republic): chemistry and genesis

Yurichev A. N., Rozenbush A. A., Kulkov A. S.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 1. P. 100-111

Full text is available on eLIBRARY.RU

Language: Russian

Abstract

Object of the study is previously undefined uvarovite garnets of Agardag ultramafic massif in South Tyva. Their typomorphic features and chemical composition have been investigated for the first time. These minerals occur both in form of crystals and as fine-grained aggregates in close association with calcite, serpentine and chromium-bearing chlorite. According to decreasing contents of minals in chemical composition, there were distinguished three joins of calcium-chromium garnets: uvarovite-grossular, uvarovite-grossular-andradite, and uvarovite-andradite-grossular. Minerals of uvarovite-grossular join have composition close to uvarovite garnets of Saranovsky (the Middle Urals) and Dlinnogorsky (Koryakia) ultramafic massifs, but differing from them by somewhat higher Fe content and complete absence of TiO₂. According to their genetic nature, studied uvarovite garnets belong to apo-ultramafic hydrothermal formation, this is confirmed by their typomophic features, coexisting minerals and constantly remarked structures of dissolution on crystal faces.

Key words: Agardag massif, chromitites, uvarovite garnets, typomorphism, chemical composition, genesis.