Garnet and spinel lherzolite assemblages in MgO-Al 2O 3-SiO 2 and CaO-MgO-Al 2O 3-SiO 2: Thermodynamic models and an experimental conflict

Abstract

The recent publication of an updated thermodynamic dataset for petrological calculations provides an opportunity to illustrate the relationship between experimental data and the dataset, in the context of a new set of activity-composition models for several key minerals. These models represent orthopyroxene, clinopyroxene and garnet in the system CaO-MgO-Al 2O 3-SiO 2 (CMAS), and are valid up to 50kbar and at least 1800°C; they are the first high-temperature models for these phases to be developed for the Holland & Powell dataset. The models are calibrated with reference to phase-relation data in the subsystems CaO-MgO-SiO 2 (CMS) and MgO-Al 2O 3-SiO 2 (MAS), and will themselves form the bas..