MINERAL-MELT EQUILIBRIA IN A HYDROUS BASA LTIC SYSTEM - COMPUTER MODELING

A method is proposed for using experimental data on phase equilibria i n igneous rocks to develop a computer model of basalt magma crystalliz ation under hydrous conditions. The approach includes: (1) the develop ment of an empirical relation for the calculation of water solubility in basalt, andesite, and granite melt as a function of composition, te mperature, and pressure; (2) estimating on the basis of this relation the water concentration in quench glasses produced in experiments on t he melting of rocks under water-saturated conditions; (3) calculation of correction coefficients accounting for the various water effects on the liquidus temperature of main mineral phases in the basaltic syste m; and (4) development of an algorithm for the modeling of basalt magm a crystallization on the basis of the obtained relations. With the mod ified ''hydrous'' version of the COMAGMAT software, phase equilibrium calculations for a high-alumina basaltic melt at P-H2O = 2 kbar well r eproduce the experimental data on the composition of water-saturated m elts, equilibrium temperature, and the proportion of crystallizing min erals.