Towards Simultaneous Sound Velocity and EoS Measurements to Lower Mantle Conditions

Baosheng Li¹, Jennifer Kung¹, Yanbin Wang², Takeyuki Uchida², Kelly Woody¹, Robert C. Liebermann¹, Donald Weidner¹, Mark Rivers², Stephen Sutton²

¹Mineral Physics Institute, SUNY Stony Brook

²GSECARS, APS, University of Chicago)

Baosheng.Li@sunysb.edu

APS-GSECARS

Combined ultrasonic technique and synchrotron X-radiation facilities allows us to measure sound velocities, equation of state (unit cell parameters), and axial strain (sample length change) simultaneously at high pressure and temperature. These measurements not only yield redundant determination of elastic properties of Earth materials, but also provide an independent determination of pressure without using secondary pressure scales such as NaCl, Au, etc. It is feasible in the laboratory to conduct such measurements on millimeter-sized solid and liquid Earth materials to P> 10 GPa T>1600K using DIA-type apparatus (SAM85) installed at X-17B2, NSLS/BNL, and P > 25 GPa, T>1500K using the multi-anvil apparatus installed at GSECARS, Advanced Photon Source. We have applied these advanced techniques to the study of major mantle silicate phases, including fosterite, wadsleyite and ringwoodite phases of (MgFe)₂SiO₄, MgSiO₃ orthopyroxene, CaSiO₃ perovskites, and (Mg,Fe,Al)-silicate perovskites. Latest measurements on a MgSiO₃ perovskite sample have been conducted to pressures greater than 27 GPa at room temperature. In addition, we also work actively on measurements on pressure standard materials, such as MgO, NaCl, Au, and Pt, towards a precise pressure scale for high pressure experiments to lower mantle conditions. Upon completion of all these measurements, we will have precise elasticity data that can be compared with seismic data directly without extrapolations in pressure and temperature.