Thermoelastic Properties of Fayalite at High Temperatures and High Pressures

Fayalite (Fe2SiO4), the Fe-rich end-member of the olivine solid-solution series, is a key mineral in governing the thermodynamic behavior of Fe-rich planetary mantles. Here, using an iterative numerical approach constrained by previous experimental data, we extracted the volume, elastic properties, and, most importantly, the thermodynamic properties, including thermal expansion, isobaric heat capacity, entropy, and the Grüneisen parameter of fayalite up to 20 GPa and 2000 K. Our results demonstrate that all these thermodynamic properties are positively correlated with temperature but negatively correlated with pressure. Also, thermal expansion, isobaric heat capacity, entropy, and the Grüneisen parameter of fayalite are generally higher than those of San Carlos olivine, but show lower pressure dependence. This work provides a comprehensive thermodynamic dataset for modelling phase equilibria in the Fe–Mg olivine system and for refining interpretations of the thermal state of iron-rich planetary mantles.