High-temperature heat capacity of grossular (Ca3Al2Si3O12), enstatite (MgSiO3), and titanite (CaTiSiO5)

The heat capacities of synthetic grossular (Ca3Al2Si3O12), ortho- and proto enstatite (MgSiO3), and titanite (CaTiSiO5) were determined from drop-calor imetry measurements made between 400 K and 1390, 1811, and 1809 K, respecti vely. The hear capacity of grossular increases smoothly with temperature be fore leveling off in an anomalous way above 1500 K. For enstatite, no large heat capacity difference seems to occur between the ortho- and protoenstat ite forms although important premelting effects are observed for protoensta tite above 1700 K. Our results for titanite up to the melting point confirm the minimal calorimetric effects at the para-antiferroelectric transition near 500 K and the large magnitude of the premelting enthalpy, which repres ents about 25% of the reported enthalpy of fusion.