HR: 14:55h
AN: MR33B-06 INVITED     [Abstracts]
TI: Elasticity and sound velocities of aluminous MgSiO3 perovskite and ferropericlase at high-pressure
AU: * Jackson, J M
EM: jjackson@aps.anl.gov
AF: Advanced Photon Source, XFD, 431-D010 9700 S. Cass Ave., Argonne, IL 60439 United States
AB: Accurate determinations of the sound velocities of deep Earth materials under the relevant pressures and temperatures are essential for understanding seismic observations in this region. Aluminum-bearing (Mg,Fe)SiO₃ perovskite and (Mg,Fe)O ferropericlase have been proposed to be abundant phases in Earth's lower mantle, with aluminous perovskite occupying roughly half of Earth's volume. Despite their major roles in the deep Earth, very little is known about the sound velocities of these chemically complex phases under appropriate lower mantle conditions. We will present high-pressure measurements on the sound velocities and elasticity of polycrystalline aluminous MgSiO₃ perovskite (containing 5 wt.% Al₂O₃) to 45 GPa and single-crystal (Mg_0.94Fe_0.06)O ferropericlase to 20 GPa. The measurements were made at room temperature by Brillouin spectroscopy with diamond anvil cells using methanol-ethanol-water or neon as pressure-transmitting media. The results give insight into whether observed lateral variations of seismic wave speeds in the lower mantle are due at least in part to a chemical origin. In both cases, the shear properties of the materials are important factors in the conclusions reached. We will also discuss our elasticity results obtained from Brillouin spectroscopy in light of existing static compression measurements from x-ray diffraction on the same materials.
DE: 3900 MINERAL PHYSICS
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005