The Peculiarities of Crystallization of Lithium-Containing Granite Melt with High Water and Fluorine Contents in the Temperature Range of 800 - 400 °C and Pressure of 1 kbar (According to Experimental Data).

The phase relations in the Si-Al-Na-K-Li-F-H-O model granite system were studied experimentally at T=800, 700°C and P=1 and 2 kbar, as well as at T=600, 550, 500 and 400°C and P=1 kbar and different water content from 2 to 50 wt.%. It is shown that two immiscible melts are formed in the system – aluminosilicate (L) and salt alkali-aluminofluoride (LF) in the presence of Li in liquidus conditions. The experiments were carried out on a high gas pressure unit in the IEM RAS. It is shown that at T=800°C, P=1 and 2 kbar and water content >10 wt.% equilibrium in the system are three phases: L, LF and fluid (Fl). At 700°C, cryolite (Crl), begins to crystallize from the salt melt. At 600°C, quartz (Qtz) crystallizes from the aluminosilicate melt, the equilibrium phases are: L, LF, Crl, Qtz. At T=500°C from L crystallizes Qtz, Na and K aluminofluorides and polylithionite. Сrystals of cryolite and elpasolite are formed in the salt melt. In this case, the residual salt melt enriched with Li and REE is preserved. At 400°C, LF completely crystallizes, and L is in a metastable state in the form of glass. It is found that REE, Sc, Y and Li accumulate in the salt melt up to 500°C with separation coefficients >>1. At T=500 and 400°C, REE and Sc are part of the crystal phases. Sc partially replaces Al in fluorides and micas. REE most often forms its own fluoride phases of the LnF₃ type.