GEOFLUID - A FORTRAN-77 PROGRAM TO COMPUTE CHEMICAL-PROPERTIES OF GAS SPECIES IN C-O-H FLUIDS

Volatile solutions composed of gas species constrained by the three-component system C-O-H are encountered in igneous, ore geological, or metamorphic settings. These fluids contain important information on the geochemistry of the system in which the fluids equilibrated. Because the calculations of geochemical parameters in these solutions is a time-consuming and complex procedure, a FORTRAN 77 application termed ''GEOFLUID'' was written to allow easy and flexible computations and modeling on C-O-H fluids. The geochemical scenarios which are considered by ''GEOFLUID'' are: (1) calculation of fluid specification in graphite buffered C-O H solutions; (2) calculation of f(O2) and log K in C-O-H fluids of known composition and not buffered by graphite; (3) calculation of molar volumes and fugacity coefficients of pure species. The output data depends on the request made by the user but includes: fluid speciation; f(O2) at various buffer conditions; fugacity coefficients and molar volumes for H2O, H-2, CH4, CO2, and CO; and log K for various equilibrium reactions between the gas species in the C-O-H system. GEOFLUID uses a variety of equations of state from the literature which in combination cover a temperature range of 450-3000 K and a pressure range of 1 bar-1 Mbar.