FLUORITE SOLUBILITY IN AQUEOUS-SOLUTIONS OF NACL, CACL2, AND THEIR MIXTURES AT 40-600-DEGREES-C AND 2 KBAR

The solubility of synthetic monocrystalline fluorite in individual aqu eous solutions of NaCl (1-34.7 m) at 400, 500, and 600 degrees C, CaCl 2 (0.5-5 m) at 500 and 600 degrees C), and in mixed NaCl-CaCl2 solutio ns (10 mol Cl-tot/kg H2O) at 500 degrees C was measured by the weight loss method. The log-log dependence of the isothermal solubilities on the chloride concentration, with the exception of the 400 degrees C is otherm, was linear over the whole range of chloride concentration stud ied. In the mixed solutions, the curve of constant chloride concentrat ion has a minimum for Na/(Na + Ca) ratio near 0.95. The solubility in CaCl2 solutions exceeds that in NaCl solutions of the same concentrati on by more than a half-order of magnitude. From the slope of the isoth erms, in NaCl solutions at 600 degrees C Na2ClF2 degrees was identifie d and NaCaClF2, Na2ClF2 + CaClF2, and Na2CaF2Cl2, at 500 degrees C; in CaCl2 solutions, Ca2Cl(2)F(2) degrees was identified at 500-600 degre es C. The conclusion was made that in a natural environment, fluorite can form not only as a result of direct cooling of a fluid, but also d ilution of the ore-bearing fluid by colder, low-mineralized (vadose) w aters.