Thermal equation of state of (Mg_0.9Fe_0.1)₂SiO₄ olivine

In situ synchrotron X-ray diffraction measurements have been carried out on San Carlos olivine (Mg_0.9Fe_0.1)₂SiO₄ up to 8 GPa and 1073 K. Data analysis using the high-temperature Birch-Murnaghan (HTBM) equation of state (EoS) yields the temperature derivative of the bulk modulus (∂K_T/∂T)_P = -0.019 ± 0.002 GPa K^-1. The thermal pressure (TH) approach gives αK_T = 4.08 ± 0.10 × 10^-3 GPa K^-1, from which (∂K_T/∂T)_P = -0.019 ± 0.001 GPa K^-1 is derived. Fitting the present data to the Mie-Grüneisen-Debye (MGD) formalism, the Grüneisen parameter at ambient conditions γ₀ is constrained to be 1.14 ± 0.02 with fixed volume dependence q = 1. Combining the present data with previous results on iron-bearing olivine and fitting to MGD EoS, we obtain γ₀ = 1.11 ± 0.01 and q = 0.54 ± 0.36. In this study the thermoelastic parameters obtained from various approaches are in good agreement with one another and previous results.