Elastic Properties of (MgX,Fe1-X)O Solid-solution at High Pressure

Ferropericlase, (Mg,Fe)O, is widely believed to be a major phase in the lower mantle of the Earth, coexisting with Mgrich silicate perovskite, (Mg,Fe,Al)SiO3. Experiments on Mg/Fe partitioning at high pressures suggest that the FeO content in this ferropericlase phase lies in the range 10-20 mol% for potential composition models of the Earth's mantle (e.g. [1]). To date, the elasticity measurements of (Mg,Fe)O phase have been focused on the end-members MgO and FeO at high pressure or high temperature [2-4]. The elasticity studies on the effect of the Fe-substitution into MgO-periclase were conducted at ambient conditions [5, 6]. Static compression studies have explored higher pressure behavior, but provided only indirect determination of the isothermal bulk modulus and its pressure-, temperature derivatives, and no information on the shear properties [7]. This has limited us the ability of exploring the physical state of the lower mantle. Now, the elastic properties of (Mg,Fe)O can be determined at mantle conditions using the ultrasonic measurement in conjunction with in-situ X-radiation techniques in high pressure apparatus. In this study, we explored the effect of Fe-content on the (Mg,Fe)O phase at high pressure.