Geochemical Specifics of Highly Differentiated Topaz-Bearing Granite of the Salmi Batholith
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Two varieties of highly differentiated topaz-bearing granite of the Salmi Batholith are distinguished: Li-siderophyllite topaz-bearing granite (Li-Sdph) (Lupikko dome) and Li–F-topaz-zinnwaldite granite (Li–F-Znwl) (Uksinskii dome). Their geochemical patterns and their place in the evolution of the compositions of A-type granite magma derivatives are shown using indicators of crystallization differentiation and the mineragenic potential; the likely regime of the volatile components (water activity in the melt and F accumulation) is discussed. The physicochemical conditions of the formation of Li–F granite were studied. The solidus temperature was determined experimentally by the method of rock powder melting (570–640°C under water saturated and dry conditions). Based on the temperatures of rock formation obtained and the data on the composition of micas, the F content in the fluid in equilibrium with micas (~0.24–0.34 mol/dm3 HF) was estimated. This similarity of the evolutionary trends for granite magmatism of the studied rocks and commercial Ta–Nb objects of Eastern Transbaikalia (S-type granite) is shown.
The authors are grateful to M.O. Anosova, N.V. Vasil’ev, V.K. Karandashev, E.A. Minervina, A.N. Nekrasov, A.I. Yakushev, and V.O. Yapaskurt for precise analyses. This study was supported by the Russian Foundation for Basic Research, project nos. 18-05-01101-A and 18-05-01001-A.
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