Ultra High-Pressure Equation of State and Melting of MgSiO3

Dylan Spaulding, University of California, Berkeley

Photo of Dylan Spaulding

New laser-driven shock experiments, using both single-crystal and glass starting materials, extend equation of state measurements on MgSiO3 to 4.5 Mbar and 15,000 K. Simultaneous collection of temporally and spatially resolved velocimetry, pyrometry and reflectivity data document shock-induced melting at pressures above 275 GPa, with an apparent increase in optical reflectivity (>20%) and density (several percent). These observations indicate transformation to a metallic state upon melting, implying that the distinction between silicate and metallic constituents are blurred at Earth’s core-mantle boundary. This was particularly the case at the high temperatures and pressures present after the late-stage giant impact that formed the Moon.

Abstract Author(s): D.K. Spaulding [1], R. Jeanloz [1], R. McWilliams [2], J. Eggert [3], D. Hicks [3], P. Celliers [3], G.W. Collins [3]; 1. Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767; 2. Institute for Shock Physics, Washington State University, Pullman, WA 99164-1227; 3. Shock Physics Group, Physics and Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550