Extension of (Mg0.64Fe0.36)O Ferropericlase Equation of State Measurements to 25 GPa and 2173 K

We present an updated equation of state (EOS) for (Mg_0.64Fe_0.36)O ferropericlase (FP), the most voluminous oxide in the Earth's lower mantle, based on a new set of PVT measurements. FP volumes were determined in situ in a multi-anvil apparatus, at pressures up to 25 GPa and temperatures up to 2173 K, with energy-dispersive X-ray diffraction at the SPring-8 synchrotron facility. Au and MgO were used as pressure markers. Including previous measurements by Fei et al. (PCM 1992) and Zhang and Kostak (PEPI 2002), 165 PVT points are now available for this material. Data were fitted to high-temperature Birch-Murnaghan and Mie-Grüneisen-type EOS. As an example of the attainable accuracy, our Birch-Murnaghan EOS reproduces experimental pressures for all 165 data points to within 0.28 GPa (1σ ), with a maximum deviation of 0.8 GPa. The revised FP EOS is compared with recent EOS data for pure MgO, to assess possible variations in FP thermodynamic properties at lower mantle PT conditions as a function of FP iron content.