Calculation of mass transfer in geochemical processes involving aqueous solutions

Abstract Differential equations providing for simultaneous dissolution of multiple reactant minerals, precipitation of mineral assemblages, variable activity of H 2 O, oxidation-reduction reactions, binary solid solution, and changes in activity coefficients in both open and closed systems are incorporated in a grand matrix equation describing mass transfer in geochemical processes. Computer evaluation of this equation affords quantitative prediction of the extent to which minerals are produced and/or destroyed as well as changes in the composition of phases and distribution of species in geologic systems in which an irreversible reaction takes place between a given mineral or mineral assemblage and an aqueous solution at constant temperature and pressure. Computers and thermodynamic data currently available permit mass transfer calculations to be carried out for systems involving more than 60 components, phases, and chemical species at temperatures up to 300°C.