Calculation of phase equilibrium in mineral-melt systems

Abstract This paper presents a general method for the calculation of mineral-melt phase equilibria based on mass balance, stoichiometry, and single component distribution coefficients. An algorithm for the practical application of this method is developed, and a computer program using this algorithm for calculation of phase stability, phase proportions, and phase composition has been included. The program includes both equilibrium and fractional models for melting and crystallization. This particular implementation incorporates a specific distribution coefficient model for olivine, plagioclase, and clinopyroxene crystallization in basaltic systems. Calculated results from the program agree with those from experiments on terrestrial basaltic compositions. The program has been designed to be modified easily to incorporate other distribution coefficient models for detailed application to specific data sets. In this way, the program should be able to be applied to diverse compositions, phase assemblages, and physical processes of crystal/liquid interaction. In general, the algorithm and its implementation provide a practical method for calculating equilibria in multicomponent, mineral-melt systems.

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