Elasticity of forsterite to 16 GPa and the composition of the upper mantle

Thomas S. Duffy, Chang Sheng Zha, Robert T Downs, Ho Kwang Mao, Russell J. Hemley

Research output: Contribution to journalArticle

150 Citations (Scopus)

Abstract

NEARLY 60 years ago, Bernai1 proposed that a polymorphic phase transformation in olivine might be responsible for the seismic velocity discontinuity near 410 km depth in the mantle. Phase equilibria experiments2,3 have since shown that the olivine (α) to wadsleyite (β) transition in (Mg,Fe)2SiO4 occurs at the appropriate pressure (13.8GPa) under mantle conditions. Comparison of laboratory measurements of the acoustic velocity contrast in the α-β system to the magnitude of the seismically observed discontinuity at 410 km provides a way to constrain the olivine content of the mantle at this depth. Here we report measurements of the full set of elastic moduli of single-crystal forsterite (α-Mg2SiO4) at pressures between 3 and 16 GPa, using Brillouin scattering in a diamond anvil cell. At 13.8 GPa, the aggregate compressionaland shear-wave velocities of α-Mg2SiO4 are 2.7 ±0.7% lower than predicted from earlier low-pressure data4,5. From our data, and assuming a homogeneous mantle composition, the seismic velocity contrast at 410 km depth can be satisfied only by a mantle containing less than ∼40% olivine. This is well below the olivine abundance assumed in peridotite-based upper-mantle models.

Original languageEnglish (US)
Pages (from-to)170-173
Number of pages4
JournalNature
Volume378
Issue number6554
StatePublished - Nov 9 1995
Externally publishedYes

Fingerprint

forsterite
elasticity
upper mantle
olivine
mantle
seismic velocity
discontinuity
wadsleyite
diamond anvil cell
elastic modulus
phase equilibrium
peridotite
wave velocity
low pressure
S-wave
acoustics
scattering
crystal

ASJC Scopus subject areas

  • General

Cite this

Duffy, T. S., Zha, C. S., Downs, R. T., Mao, H. K., & Hemley, R. J. (1995). Elasticity of forsterite to 16 GPa and the composition of the upper mantle. Nature, 378(6554), 170-173.

Elasticity of forsterite to 16 GPa and the composition of the upper mantle. / Duffy, Thomas S.; Zha, Chang Sheng; Downs, Robert T; Mao, Ho Kwang; Hemley, Russell J.

In: Nature, Vol. 378, No. 6554, 09.11.1995, p. 170-173.

Research output: Contribution to journalArticle

Duffy, TS, Zha, CS, Downs, RT, Mao, HK & Hemley, RJ 1995, 'Elasticity of forsterite to 16 GPa and the composition of the upper mantle', Nature, vol. 378, no. 6554, pp. 170-173.
Duffy TS, Zha CS, Downs RT, Mao HK, Hemley RJ. Elasticity of forsterite to 16 GPa and the composition of the upper mantle. Nature. 1995 Nov 9;378(6554):170-173.
Duffy, Thomas S. ; Zha, Chang Sheng ; Downs, Robert T ; Mao, Ho Kwang ; Hemley, Russell J. / Elasticity of forsterite to 16 GPa and the composition of the upper mantle. In: Nature. 1995 ; Vol. 378, No. 6554. pp. 170-173.
@article{287110c7795d47e4b8b435ceaffc4d98,
title = "Elasticity of forsterite to 16 GPa and the composition of the upper mantle",
abstract = "NEARLY 60 years ago, Bernai1 proposed that a polymorphic phase transformation in olivine might be responsible for the seismic velocity discontinuity near 410 km depth in the mantle. Phase equilibria experiments2,3 have since shown that the olivine (α) to wadsleyite (β) transition in (Mg,Fe)2SiO4 occurs at the appropriate pressure (13.8GPa) under mantle conditions. Comparison of laboratory measurements of the acoustic velocity contrast in the α-β system to the magnitude of the seismically observed discontinuity at 410 km provides a way to constrain the olivine content of the mantle at this depth. Here we report measurements of the full set of elastic moduli of single-crystal forsterite (α-Mg2SiO4) at pressures between 3 and 16 GPa, using Brillouin scattering in a diamond anvil cell. At 13.8 GPa, the aggregate compressionaland shear-wave velocities of α-Mg2SiO4 are 2.7 ±0.7{\%} lower than predicted from earlier low-pressure data4,5. From our data, and assuming a homogeneous mantle composition, the seismic velocity contrast at 410 km depth can be satisfied only by a mantle containing less than ∼40{\%} olivine. This is well below the olivine abundance assumed in peridotite-based upper-mantle models.",
author = "Duffy, {Thomas S.} and Zha, {Chang Sheng} and Downs, {Robert T} and Mao, {Ho Kwang} and Hemley, {Russell J.}",
year = "1995",
month = "11",
day = "9",
language = "English (US)",
volume = "378",
pages = "170--173",
journal = "Nature",
issn = "0028-0836",
publisher = "Nature Publishing Group",
number = "6554",

}

TY - JOUR

T1 - Elasticity of forsterite to 16 GPa and the composition of the upper mantle

AU - Duffy, Thomas S.

AU - Zha, Chang Sheng

AU - Downs, Robert T

AU - Mao, Ho Kwang

AU - Hemley, Russell J.

PY - 1995/11/9

Y1 - 1995/11/9

N2 - NEARLY 60 years ago, Bernai1 proposed that a polymorphic phase transformation in olivine might be responsible for the seismic velocity discontinuity near 410 km depth in the mantle. Phase equilibria experiments2,3 have since shown that the olivine (α) to wadsleyite (β) transition in (Mg,Fe)2SiO4 occurs at the appropriate pressure (13.8GPa) under mantle conditions. Comparison of laboratory measurements of the acoustic velocity contrast in the α-β system to the magnitude of the seismically observed discontinuity at 410 km provides a way to constrain the olivine content of the mantle at this depth. Here we report measurements of the full set of elastic moduli of single-crystal forsterite (α-Mg2SiO4) at pressures between 3 and 16 GPa, using Brillouin scattering in a diamond anvil cell. At 13.8 GPa, the aggregate compressionaland shear-wave velocities of α-Mg2SiO4 are 2.7 ±0.7% lower than predicted from earlier low-pressure data4,5. From our data, and assuming a homogeneous mantle composition, the seismic velocity contrast at 410 km depth can be satisfied only by a mantle containing less than ∼40% olivine. This is well below the olivine abundance assumed in peridotite-based upper-mantle models.

AB - NEARLY 60 years ago, Bernai1 proposed that a polymorphic phase transformation in olivine might be responsible for the seismic velocity discontinuity near 410 km depth in the mantle. Phase equilibria experiments2,3 have since shown that the olivine (α) to wadsleyite (β) transition in (Mg,Fe)2SiO4 occurs at the appropriate pressure (13.8GPa) under mantle conditions. Comparison of laboratory measurements of the acoustic velocity contrast in the α-β system to the magnitude of the seismically observed discontinuity at 410 km provides a way to constrain the olivine content of the mantle at this depth. Here we report measurements of the full set of elastic moduli of single-crystal forsterite (α-Mg2SiO4) at pressures between 3 and 16 GPa, using Brillouin scattering in a diamond anvil cell. At 13.8 GPa, the aggregate compressionaland shear-wave velocities of α-Mg2SiO4 are 2.7 ±0.7% lower than predicted from earlier low-pressure data4,5. From our data, and assuming a homogeneous mantle composition, the seismic velocity contrast at 410 km depth can be satisfied only by a mantle containing less than ∼40% olivine. This is well below the olivine abundance assumed in peridotite-based upper-mantle models.

UR - http://www.scopus.com/inward/record.url?scp=0029535058&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0029535058&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0029535058

VL - 378

SP - 170

EP - 173

JO - Nature

JF - Nature

SN - 0028-0836

IS - 6554

ER -