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Title: Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle

Abstract

The partial phonon densities of states of iron in magnesiowuestite [(Mg{sub 0.75},Fe{sub 0.25})O] have been measured by nuclear inelastic X-ray scattering up to 109 GPa. Compressional and shear wave velocities, shear moduli, and their pressure derivatives increase significantly across the spin-pairing transition of iron in (Mg{sub 0.75},Fe{sub 0.25})O at approximately 50 GPa. The effects of the transition on the elastic properties of (Mg,Fe)O at lower-mantle pressures are in contrast to what was predicted by studying MgO and high-spin magnesiowuestite, and need to be considered in future geophysical modeling of the lower mantle. The transition also affects other thermodynamic properties of magnesiowuestite under high pressures.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
898494
Report Number(s):
UCRL-JRNL-218397
TRN: US0701665
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geophysical Research Letters, vol. 33, N/A, November 18, 2006, L22304
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ELASTICITY; IRON; PHONONS; SCATTERING; SHEAR; SIMULATION; THERMODYNAMIC PROPERTIES

Citation Formats

Lin, J, Jacosben, S D, Sturhahn, W, Jackson, J, Zhao, J, and Yoo, C. Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle. United States: N. p., 2006. Web.
Lin, J, Jacosben, S D, Sturhahn, W, Jackson, J, Zhao, J, & Yoo, C. Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle. United States.
Lin, J, Jacosben, S D, Sturhahn, W, Jackson, J, Zhao, J, and Yoo, C. Fri . "Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle". United States. doi:. https://www.osti.gov/servlets/purl/898494.
@article{osti_898494,
title = {Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle},
author = {Lin, J and Jacosben, S D and Sturhahn, W and Jackson, J and Zhao, J and Yoo, C},
abstractNote = {The partial phonon densities of states of iron in magnesiowuestite [(Mg{sub 0.75},Fe{sub 0.25})O] have been measured by nuclear inelastic X-ray scattering up to 109 GPa. Compressional and shear wave velocities, shear moduli, and their pressure derivatives increase significantly across the spin-pairing transition of iron in (Mg{sub 0.75},Fe{sub 0.25})O at approximately 50 GPa. The effects of the transition on the elastic properties of (Mg,Fe)O at lower-mantle pressures are in contrast to what was predicted by studying MgO and high-spin magnesiowuestite, and need to be considered in future geophysical modeling of the lower mantle. The transition also affects other thermodynamic properties of magnesiowuestite under high pressures.},
doi = {},
journal = {Geophysical Research Letters, vol. 33, N/A, November 18, 2006, L22304},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2006},
month = {Fri Jan 20 00:00:00 EST 2006}
}
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  • No abstract prepared.
  • The compressional and shear wave velocities for coesite have been measured simultaneously up to 5.8 GPa and 1073 K by ultrasonic interferometry for the first time. The shear wave velocity decreases with pressure along all isotherms. The resulting contrasts between coesite and stishovite reach ~34% and ~45% for P and S wave velocities, respectively, and ~64% and ~75% for their impedance at mantle conditions. The large velocity and impedance contrasts across coesite-stishovite transition imply that to generate the velocity and impedance contrasts observed at the X-discontinuity, only a small amount of silica would be required. The velocity jump dependences onmore » silica, d(lnVP)/d(SiO2) = 0.38 (wt %)-1 and d(lnVS)/d(SiO2) = 0.52 (wt %)-1, are utilized to place constraints on the amount of silica in the upper mantle and provide a geophysical approach to track mantle eclogite materials and ancient subducted oceanic slabs.« less