Formation of Cryolite in Granites of the Katugin Deposit from the Position of the Results of Experiments in a Fluorine-Lithium-Containing Granite System

The parageneses of cryolite-containing granites of the rare-metal Katugin deposit are studied and compared with the experimental results for the fluorine-lithium-containing granite system. According to the experiment, cryolite crystallization begins from the salt melt, which is in equilibrium with the aluminosilicate melt, at 700°C and 1 kbar. In the temperature range of 500–600°C and a pressure of 1 kbar, cryolite crystallizes together with quartz from the aluminosilicate melt. Rare earth elements are distributed in the fluorine-lithium-containing granite system mainly in favor of the salt alkali-aluminofluoride melt. It is shown that the formation of cryolite and associated rare earth minerals is possible at the magmatic stage of the Katugin deposit formation due to silicate-salt immiscibility in granite melts at late stages of differentiation.