Sound velocities and elastic constants of iron-bearing hydrous ringwoodite

Steven D. Jacobsen*, Joseph R. Smyth, Hartmut Spetzler, Christopher M. Holl, Daniel J. Frost

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

131 Scopus citations

Abstract

The sound velocities and single-crystal elastic constants of Fo89 hydrous ringwoodite (γ-Mg1.7 Fe0.22H0.16SiO4) containing ∼10,000 ppm by weight (1 wt.%) H2O have been determined from seven separate pure-mode travel-time measurements using gigahertz ultrasonic interferometry. The experiments feature a new Yttrium-Aluminum- Garnet (YAG) P-to-S conversion shear buffer rod (BR), capable of producing pure ultrasonic shear waves with known polarization in the region of 0.5-2.0 GHz. To our knowledge they are the first such single-crystal ultrasonic measurements on a high-pressure phase recovered from the multi-anvil press. The cubic single-crystal elastic constants of hydrous Fo89 ringwoodite at ambient conditions are (in GPa): c11 = 298 ± 13, c44 = 112 ± 6, and c12 = 115 ± 6. Hydration of Fo∼90 ringwoodite to 1 wt.% H2O reduces the adiabatic bulk (K0S = 176 ± 7 GPa) and shear (G = 103 ± 5 GPa) moduli by about 6 and 13%, roughly equivalent to raising the temperature at room pressure by 600 and 1000 °C, respectively. Assuming a linear trend with hydration, we calculate that P- and S-wave velocities are reduced by about 40 m/s for every 1000 ppm weight (0.1 wt.%) H2O added to Fo∼90 ringwoodite. P- and S-wave velocities of the lower transition zone in PREM are consistent with a hydrated ringwoodite-rich composition.

Original languageEnglish (US)
Pages (from-to)47-56
Number of pages10
JournalPhysics of the Earth and Planetary Interiors
Volume143
Issue number1-2
DOIs
StatePublished - Jun 15 2004

Keywords

  • Elastic properties
  • Gigahertz ultrasonic interferometry
  • Hydrogen in the transition zone
  • Hydrous ringwoodite

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science

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