Аннотация:Experimental results of behavior of natural minerals of pyrochlore and tantalite in solutions KF, NaF and LiF in the presence of quartz (granite) at T = 550°–850 °C, P=1 kbar are presented. The considerable influence of silicate substance presence on mineral solubility in water solutions of alkali metal fluorides in hydrothermal conditions is shown. The study of fluid inclusions in quartz showedthat under experimental conditions (heterogeneous state of the fluid) the reactions of high-temperature hydrolysis KF: KF+H2O=KOH+HF, with the separation of acid and alkaline components between the immiscible phases of the fluid are intensive. In this case, the interaction of alkaline components with quartz occurs: SiO2+ 2KOH=K2SiO3+H2O, with the formation of a phase of silicate glass (aqueoussolution-melt). This phase of silicate alkaline melt enriched with fluorine concentrates tantalum and niobium (up to 8% of Ta2O5and 16% of Nb2O5) and can serve as a phase—a concentrator of ore elements in the formation of tantalum-niobate deposits at the last low-temperature stages of crystallization of rare-metal granites.