HR: 15:10h
AN: V32E-07    [PDF]
TI: Elasticity of MgSiO$_{3}$ Polycrystalline Perovskite by Brillouin Spectroscopy
AU: * Sinogeikin, S V
EM: sinogeik@uiuc.edu
AF: Geology dept. Univercity of Illinois at Urbana, 1301 W. Green St, Urbana, IL 61801 United States
AU: Zhang, J
EM: jzhang@lanl.gov
AF: LANSCE-12, MS-H805, Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 United States
AU: Bass, J D
EM: jaybass@uiuc.edu
AF: Geology dept. Univercity of Illinois at Urbana, 1301 W. Green St, Urbana, IL 61801 United States
AB: Magnesium silicate perovskite is the most abundant mineral phase in the lower mantle of the Earth. Even though it is probably the most studied high-pressure phase, its elastic properties at ambient conditions (bulk, and especially, shear modulus) remain uncertain. We have carried out a Brillouin spectroscopy study of MgSiO$_{3}$ perovskite to try to resolve discrepancies surrounding its elastic properties. The polycrystalline sample of perovskite was synthesized from pure MgSiO$_{3}$ glass starting material at SUNY, Stony Brook. The synthesis was performed at 25 GPa and 1873 K in USSA-2000 high-pressure apparatus, with an 8/3 cell assembly and rhenium heater. The perovskite structure was confirmed by X-ray and Raman spectroscopy. The Raman spectroscopy did not reveal any non-perovskite phases in the sample. The Brillouin measurements were performed on samples polished plane-parallel to 30 mkm. The measurements were performed in platelet symmetric scattering geometry, which yields compressional and shear velocities independently of the refractive index of the sample. Despite the polycrystalline nature of the sample, all spectra were of excellent quality, and the measured velocities showed very little variation from run to run. The measured aggregate velocities and elastic moduli differ significantly from those, calculated from single-crystal elastic constants measured earlier by Brillouin spectroscopy. The implications of new data to mantle mineralogy will be discussed.
DE: 1025 Composition of the mantle
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3934 Optical, infrared, and Raman spectroscopy
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting