Direct shock wave loading of MgSiO 3 perovskite to lower mantle conditions and its equation of state

Abstract

Large MgSiO 3-perovskite samples were synthesized for shock wave experiments. Shock wave data on the pre-synthesized perovskite samples up to 107 GPa yielded a linear relationship between the shock wave velocity U s and particle velocity u p described by U s = 6.47(±0.63) + 1.56(±0.31) u p. Fitting the experiment data to the Rankin–Hugoniot equation, we obtained the Grüneisen parameter γ 0 = 1.33 with q = 1. The best fitted values for the adiabatic bulk modulus K 0 S and its pressure derivative K ′ 0 S are 254(±10) GPa and 3.9(±0.17), respectively, which are in general agreement with values derived from static compression data. By direct comparison with dynamic compression data using enstatite as starting material, we observed that MgSiO 3 enstatite completely transformed into perovskite phase above 90 GPa shock pressure. Improvement of the precision in determining the Hugoniot relationship by additional shock wave data is needed to further constrain the thermoelastic properties of perovskite. However, this is the first demonstration that direct shock wave loading of the pre-synthesized perovskite samples can provide a new way to determining the thermal equation of state (EOS) of silicate perovskite without the complication of phase transformations along the Hugoniot path, ultimately leading to a better constrained thermoelastic parameters for this important mantle mineral.