HIGH-TEMPERATURE HIGH-PRESSURE PHASE EQUI LLIBRIA IN THE TERNARY-SYSTEM H2O-CO2-SALT (CACL2, NACL)

Phase equilibria surfaces in the model systems H2O-CO2-CaCl2 and H2O-C O2-NaCl have been studied experimentally using synthetic inclusions in quartz at the temperatures 500, and 700-degrees-C and pressures 3, an d 5 kbar. Nonmonotonic behavior of layering area with increasing press ure has been found in the systems: a smooth extreme of critical curve was observed under isothermal conditions and about 3 kbar pressure. Th is means that the ternary system inherit the behavior of the phase dia gram H2O-CO2. As a consequence we observe an extreme dissolution behav ior of the water - salt and CO2 phases. Spreading of the heterophase a rea in the systems with the natural fluids composition under the press ures corresponding to the middle and high metamorphic grades can expla in the appearance of CO2 phase of high-pressure metamorphites and migm atites.