Sound velocity of MgSiO3 perovskite to Mbar pressure

Motohiko Murakami, Stanislav V. Sinogeikin, Holger Hellwig, Jay D. Bass, Jie Li

Research output: Contribution to journalArticlepeer-review

85 Citations (Scopus)

Abstract

Brillouin scattering measurements of the aggregate shear wave velocities in MgSiO3 perovskite were conducted at high pressure conditions relevant to the Earth's lowermost mantle, approaching 1 Mbar. Infrared laser annealing of samples in a diamond anvil cell allowed us to obtain high quality Brillouin spectra and to drastically extend the upper limit of pressure for Brillouin measurements. We found that the pressure derivative of the shear modulus (dG / dP = G′) of MgSiO3 perovskite is 1.56 ± 0.04, which is distinctly lower than that of previous lower-pressure experiments below 9 GPa. Extrapolation of the high-pressure shear velocities of perovskite to ambient pressure, are in excellent agreement with earlier room pressure Brillouin measurements. The shear modulus, shear velocity and longitudinal velocity at ambient pressure were determined to be G0 = 172.9(15) GPa, VS = 6.49(3) and VP = 10.85(3) km/sec. The mineralogical model that provides a best fit to global seismological 1-D velocity profiles is one that contains 85-90 vol% perovskite in the lower mantle. The results of this study are the first to demonstrate that the elastic wave velocities for a near-adiabatic lower mantle with a bulk composition dominated by magnesium silicate perovskite are consistent with the average lower mantle seismic velocity structure. The large pressure range over which acoustic measurements of MgSiO3 perovskite performed in this study has thus allowed us to put tighter constraints on compositional models of the Earth's lower mantle.

Original languageEnglish
Pages (from-to)47-54
Number of pages8
JournalEarth and Planetary Science Letters
Volume256
Issue number1-2
DOIs
Publication statusPublished - 2007 Apr 15

Keywords

  • Brillouin scattering
  • MgSiO perovskite
  • elastic properties
  • high pressure
  • lower mantle
  • perovskite
  • sound velocity

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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