A thermodynamic model for multicomponent melts, with application to the system CaO-Al2O3-SiO2

摘要: A thermodynamic model is proposed for calculation of liquidus relations in multicomponent systems geologic interest. In this formulation mineral-melt equilibria, reactions are written terms the liquid oxide components, and balanced on stoichiometry phases. order to account non-ideality liquid, a ‘Margules solution’ derived generalized form which can be extended any number components polynomials degree. Equations presented both excess Gibbs free energy solution component activity coefficients. Application system CaO-Al2O3-SiO2 at one atmosphere pressure achieved using linear programming. Thermodynamic properties minerals melt determined consistent with adopted error brackets available calorimetric phase equilibrium data. Constraints from relations, CaO-SiO2 binary immiscibility gap, solid-solid P-T reactions, measured standard state entropies, enthalpies, volumes system. Binary ternary diagrams recalculated by computer programs trace cotectic boundaries isothermal sections while checking each point curve metastability. The maximum differences between calculated experimentally invariant points involving stoichiometric 17°C 1.5 weight per cent. Because no solid models have been incorporated, deviations larger involve non-stoichiometric minerals. Calculated heats fusion, silica activities melt, mixing liquids compare favorably experimental data, suggest that used supplement limited amount data properties.