Calculation of phase relations involving haplogranitic melts using an internally consistent thermodynamic dataset

A simple thermodynamic model is developed foe silicate melts in the system CaO-Na2O-K2O-Al2O3-SiO2-H2O (CNKASH). The Holland & Powell (Journal of Meta morphic Geology, 16, 289-302, 1998) internally consistent via the incorpora tion of the experimentally determined melting relationships in unary and bi nary subsystems of CNKASH. The predictive capability of the model is evalua ted via the experimental data in the ternary and quaternary subsystems. The resulting dataset, with the software THERMOCALC, is then used to calculate melting relationships for haplogranitic compositions. Predictions of the P -T stabilities of assemblages in water-saturated and -undersaturated bulk c ompositions are illustrated. It is now possible to make useful calculations of the melting behaviour of appropriate composition under crustal conditio ns.