High-pressure sound velocities and elasticity of aluminous MgSiO3 perovskite to 45 GPa: Implications for lateral heterogeneity in Earth's lower mantle

Abstract

Brillouin scattering measurements on aluminous magnesium silicate perovskite, arguably the most abundant phase in Earth, have been performed to 45 GPa in a diamond anvil cell at room temperature, using methanol-ethanol-water and neon as pressure transmitting media. The experiments were performed on a polycrystalline sample of aluminous MgSiO3 perovskite containing 5.1 ± 0.2 wt.% Al2O3. The pressure derivatives of the adiabatic bulk (Kos) and shear (μos) moduli are 3.7 ± 0.3 and 1.7 ± 0.2, respectively. These measurements allow us to evaluate whether the observed lateral variations of seismic wave speeds in Earth's lower mantle are due at least in part to a chemical origin. Our results indicate that a difference in the aluminum content of silicate perovskite, reflecting a variation in overall chemistry, is a plausible candidate for such seismic heterogeneity. Copyright 2005 by the American Geophysical Union.