Model for the formation of fluorine-bearing rocks in the Carboniferous deposits of the Moscow artesian basin

The paper presents the results of the statistical and thermodynamic analysis of hydrogeochemical information on the genesis of F-bearing waters in the Carboniferous deposits of the Moscow artesian basin. The F concentration is demonstrated to increase with increasing salinity of the aqueous solution. As follows from the analysis of mineral equilibria, the saturation concentrations of the aqueous phase with respect to fluorite in association with calcite and gypsum is less than 2–3 mg of F/l. At the saturation of the aqueous phase with respect to fluorite in association with dolomite, the equilibrium concentration of F increases with increasing Mg concentration and decreasing equilibrium partial CO 2 pressure and can reach 8–10 mg of F/l. The main reason for this enrichment of the aqueous phase in F is certain features of mineral equilibria in the system of aqueous solution with Ca and Mg carbonates. An increase in the Mg 2+ concentration in the aqueous phase decreases the Ca 2+ concentration in the solubility equilibrium of dolomite, and this, in turn, decreases the F − concentration in the solubility equilibrium of fluorite.