Abstract
Thermodynamic data of silicate minerals are indispensable to calculate equilibrium phase relations in the Earth's mantle. High-temperature calorimetric techniques were developed for measurements of enthalpies of solution, transition, and fusion of some silicate minerals. The heats of solution of Mg2SiO4-Fe2SiO4 olivine solid solutions were measured by lead borate solution calorimetry method. The results gave a positive mixing enthalpy for the olivines. The enthalpy of orthopyroxene-perovskite transition of MgSiO3 was obtained by differential drop-solution method. The heat of fusion of CaMgSi2O6 diopside was measured by DSC method. These thermodynamic data are used to calculate phase equilibrium boundaries at high pressures and high temperatures and are also applied to better understanding of generation of magmas.
