The Elastic Anisotropy Change Near the 410-km Discontinuity: Predictions From Single-Crystal Elasticity Measurements of Olivine and Wadsleyite

Jin S. Zhang, Jay D Bass, Brandon Schmandt

Research output: Contribution to journalArticle

Abstract

We present a model of the single-crystal elasticity of olivine with ~9-10 mol% Fe based on all available single-crystal velocity measurements. A set of finite strain equations of state that account for thermoelastic effects is used for fitting the individual elastic moduli at various pressure-temperature conditions. The same analysis is applied to reanalyze the experimentally determined single-crystal elastic moduli of hydrous and anhydrous Fe-bearing wadsleyite. Based on the obtained thermoelastic parameters of individual elastic moduli, we then calculated various elastic anisotropy indices of olivine and wadsleyite and extrapolated them to the pressure-temperature conditions expected in the Earth's mantle. The results suggest that the elastic anisotropy in the Earth's upper transition zone (410-520 km depth) is likely below the seismic detection limit if it originates primarily from the lattice preferred orientation of wadsleyite crystals. On the other hand, the elastic anisotropy of olivine is still relatively high (~19-25%) at 410 km depth. Thus, if a mantle flow field induces lattice preferred orientation of olivine and wadsleyite near 410 km depth, a reduction of elastic anisotropy is expected across the 410-km discontinuity.

Original languageEnglish (US)
JournalJournal of Geophysical Research: Solid Earth
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

wadsleyite
elastic anisotropy
olivine
elasticity
Elasticity
discontinuity
Anisotropy
anisotropy
elastic modulus
elastic properties
Single crystals
crystal
modulus of elasticity
Elastic moduli
single crystals
preferred orientation
prediction
predictions
Earth mantle
Bearings (structural)

Keywords

  • 410 discontinuity
  • Anisotropy
  • Olivine
  • Single-crystal elasticity
  • Wadsleyite

ASJC Scopus subject areas

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

Cite this

@article{0d02090950114129a3090990cf5c1791,
title = "The Elastic Anisotropy Change Near the 410-km Discontinuity: Predictions From Single-Crystal Elasticity Measurements of Olivine and Wadsleyite",
abstract = "We present a model of the single-crystal elasticity of olivine with ~9-10 mol{\%} Fe based on all available single-crystal velocity measurements. A set of finite strain equations of state that account for thermoelastic effects is used for fitting the individual elastic moduli at various pressure-temperature conditions. The same analysis is applied to reanalyze the experimentally determined single-crystal elastic moduli of hydrous and anhydrous Fe-bearing wadsleyite. Based on the obtained thermoelastic parameters of individual elastic moduli, we then calculated various elastic anisotropy indices of olivine and wadsleyite and extrapolated them to the pressure-temperature conditions expected in the Earth's mantle. The results suggest that the elastic anisotropy in the Earth's upper transition zone (410-520 km depth) is likely below the seismic detection limit if it originates primarily from the lattice preferred orientation of wadsleyite crystals. On the other hand, the elastic anisotropy of olivine is still relatively high (~19-25{\%}) at 410 km depth. Thus, if a mantle flow field induces lattice preferred orientation of olivine and wadsleyite near 410 km depth, a reduction of elastic anisotropy is expected across the 410-km discontinuity.",
keywords = "410 discontinuity, Anisotropy, Olivine, Single-crystal elasticity, Wadsleyite",
author = "Zhang, {Jin S.} and Bass, {Jay D} and Brandon Schmandt",
year = "2018",
month = "1",
day = "1",
doi = "10.1002/2017JB015339",
language = "English (US)",
journal = "Journal of Geophysical Research D: Atmospheres",
issn = "0148-0227",
publisher = "American Geophysical Union",

}

TY - JOUR

T1 - The Elastic Anisotropy Change Near the 410-km Discontinuity

T2 - Predictions From Single-Crystal Elasticity Measurements of Olivine and Wadsleyite

AU - Zhang, Jin S.

AU - Bass, Jay D

AU - Schmandt, Brandon

PY - 2018/1/1

Y1 - 2018/1/1

N2 - We present a model of the single-crystal elasticity of olivine with ~9-10 mol% Fe based on all available single-crystal velocity measurements. A set of finite strain equations of state that account for thermoelastic effects is used for fitting the individual elastic moduli at various pressure-temperature conditions. The same analysis is applied to reanalyze the experimentally determined single-crystal elastic moduli of hydrous and anhydrous Fe-bearing wadsleyite. Based on the obtained thermoelastic parameters of individual elastic moduli, we then calculated various elastic anisotropy indices of olivine and wadsleyite and extrapolated them to the pressure-temperature conditions expected in the Earth's mantle. The results suggest that the elastic anisotropy in the Earth's upper transition zone (410-520 km depth) is likely below the seismic detection limit if it originates primarily from the lattice preferred orientation of wadsleyite crystals. On the other hand, the elastic anisotropy of olivine is still relatively high (~19-25%) at 410 km depth. Thus, if a mantle flow field induces lattice preferred orientation of olivine and wadsleyite near 410 km depth, a reduction of elastic anisotropy is expected across the 410-km discontinuity.

AB - We present a model of the single-crystal elasticity of olivine with ~9-10 mol% Fe based on all available single-crystal velocity measurements. A set of finite strain equations of state that account for thermoelastic effects is used for fitting the individual elastic moduli at various pressure-temperature conditions. The same analysis is applied to reanalyze the experimentally determined single-crystal elastic moduli of hydrous and anhydrous Fe-bearing wadsleyite. Based on the obtained thermoelastic parameters of individual elastic moduli, we then calculated various elastic anisotropy indices of olivine and wadsleyite and extrapolated them to the pressure-temperature conditions expected in the Earth's mantle. The results suggest that the elastic anisotropy in the Earth's upper transition zone (410-520 km depth) is likely below the seismic detection limit if it originates primarily from the lattice preferred orientation of wadsleyite crystals. On the other hand, the elastic anisotropy of olivine is still relatively high (~19-25%) at 410 km depth. Thus, if a mantle flow field induces lattice preferred orientation of olivine and wadsleyite near 410 km depth, a reduction of elastic anisotropy is expected across the 410-km discontinuity.

KW - 410 discontinuity

KW - Anisotropy

KW - Olivine

KW - Single-crystal elasticity

KW - Wadsleyite

UR - http://www.scopus.com/inward/record.url?scp=85044865629&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85044865629&partnerID=8YFLogxK

U2 - 10.1002/2017JB015339

DO - 10.1002/2017JB015339

M3 - Article

AN - SCOPUS:85044865629

JO - Journal of Geophysical Research D: Atmospheres

JF - Journal of Geophysical Research D: Atmospheres

SN - 0148-0227

ER -