Speciation and Mineral Equilibria in the Mixed Natural Fluids H2O-non Polar Gas

Abstract

Fluid inclusion analyses indicate that natural fluids rich with dissolved non polar gases (up to 30 mole percent of CO2, N2, CH4) are widespread and play an important role in the genesis of different types of ore deposits. Physical chemistry of such fluids may be rather unconventional with comparison to the 'traditional' pure aqueous solutions. One of the main cause of the distinction is specified in the pronounced lowering of dielectric constant of the mixture because of non polar gas presence. A method tot account of this effect in mixed fluids on ionic and phase equilibria is proposed. The method is based on consistent account of solvation effects of every aqueous species, that in terms of the well known HKF equation of state (Tanger and Helgeson, 1988) refers to the modification of its chemical potential because of the change of dielectric constant of the mixed solvent, e, compared to that of pure water, aH:o