Elasticity of Ferropericlase at High Pressure and Temperature: Implications in Earth's Interior

(Mg,Fe)O is a major phase in the lower mantle of the Earth. To date, elasticity studies on (Mg,Fe)O were conducted along high-pressure regime. Static compression studies have explored the behaviors at higher P-T spaces, but provided only indirect determination of the isothermal bulk modulus and its pressure derivatives, and no information on the shear properties. By combining synchrotron X-radiation and ultrasonic velocity measurements, we are able to conduct simultaneous measurements of sound velocities using ultrasonic interferometry and unit cell parameters using X-ray diffraction, and sample length using X-radiographic imaging, at high P and T conditions (Vp-Vs-Volume-P-T). Elasticity of ferropericlase (Mg,Fe)O with 17 mole percent of Fe were measured at high pressures and temperatures. Our high temperature results for (Mg,Fe)O showed that the intrinsic contribution to the temperature derivative is weak for the adiabatic bulk moduli (Ks) and zero for the shear moduli (G). This observation is different from the "general" trend; the intrinsic temperature effect on the shear modulus tends to be greater than the bulk modulus. In this meeting, we will present and discuss the results of the elasticity of (Mg,Fe)O at high pressures and high temperatures, and the implications in the lower mantle.