Internally consistent thermodynamic data and phase relations in the CaO-Al₂O₃-SiO₂-H₂O system

Internally consistent thermodynamic data for 23 phases in the CaO-Al₂O₃-SiO₂-H₂O system are determined by linear programming consistent set analysis. The consistent set analysis is based on published experimental petrology data for equilibrium reactions involving the phases in this system. Inconsistencies in the experimental data are removed by moving four data points beyond the maximum error allowed by the specific authors or by ignoring some portions of the questionable data. The phase relations among the phases between 0 to 2000°C and 0 to 50,000 bars are calculated using the consistent thermodynamic data with the computer program PT-SYSTEM written by T.H. Brown and E.H. Perkins of the Department of Geological Sciences at the University of British Columbia. The stable portions of the 236 stable equilibrium reactions are drawn on pressure-temperature (P-T) diagrams showing the phase relations of each phase. The P-T diagrams can be used to interpret the petrogenesis of metamorphic zones containing the phases. The consistent thermodynamic data in this study can be improved by undertaking petrology experiments which will substantiate and further define the data. Experiments investigating the stability of prehnite, wairakite and heulandite are recommended. Updating of the internally consistent thermodynamic properties for existing and new phases should be carried out for each additional set of experimental data by redoing the linear programming consistent set analysis on the entire experimental data set. The new thermodynamic properties for the phases could then be used to calculate the new phase relations.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat