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Sound velocities and single-crystal elasticity of orthoenstatite to 1073 K at ambient pressure

Jackson, Jennifer M. and Sinogeikin, Stanislav V. and Bass, Jay D. (2007) Sound velocities and single-crystal elasticity of orthoenstatite to 1073 K at ambient pressure. Physics of the Earth and Planetary Interiors, 161 (1-2). pp. 1-12. ISSN 0031-9201. doi:10.1016/j.pepi.2006.11.002.

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Single-crystal Brillouin spectroscopy measurements have been carried out to 1073 K and ambient pressure to determine the elastic modulus tensor of a natural orthopyroxene, nearly pure Mg end-member (Mg_(0.994)Fe_(0.002)Al_(0.004))_2(Si_(0.996)Al_(0.004))_(2)O_6 orthoenstatite. Three single-crystal specimens with orthogonal crystallographic orientations were prepared for Brillouin measurements to determine all the single-crystal elastic moduli (C_ij). The single-crystal elastic moduli were calculated using the measured velocities of sound and our independent measurement of the volume thermal expansion. These are, to our knowledge, the highest temperatures at which the complete single-crystal elastic modulus tensor of orthoenstatite has been measured. The elastic moduli at ambient conditions obtained in this study are in excellent agreement with previous measurements on Mg_(2)Si_(2)O_6 orthoenstatite (OEN). The elastic anisotropy of OEN is approximately the same at all measured temperatures. The velocities in different directions change at different rates, with C_33 showing the largest temperature dependence (decreasing with temperature almost twice as fast as C_11 or C_22). The variation of elastic moduli with temperature is linear up to approximately 673 K, above which some of the moduli decrease with a quadratic dependence on temperature. The non-linear behavior is in accord with recent elastic mode softening observations in orthoenstatite at higher temperatures and could add support to account for a thermally induced solid-state mechanism for the low velocity zone in Earth's upper mantle.

Item Type:Article
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Jackson, Jennifer M.0000-0002-8256-6336
Additional Information:© 2007 Elsevier B.V. Received 15 March 2006; received in revised form 12 October 2006; accepted 10 November 2006. We thank George R. Rossmen (California Institute of Technology) for providing the gem quality orthoenstatite crystals (GRR 649, AMNH 100634). We would also like to thank Michael Carpenter, Ross Angel, Jennifer Kung, Dmitry L. Lakshtanov, Don Isaak,Wolfgang Sturhahn, and Lara Wagner for helpful discussions. We acknowledge support of NSF-EAR 0003383 to JDB.
Group:Seismological Laboratory
Funding AgencyGrant Number
NSFEAR 0003383
Subject Keywords:Enstatite; High-temperature; Sound velocities; Elasticity; Brillouin spectroscopy
Issue or Number:1-2
Record Number:CaltechAUTHORS:20130305-114517925
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Official Citation:Jennifer M. Jackson, Stanislav V. Sinogeikin, Jay D. Bass, Sound velocities and single-crystal elasticity of orthoenstatite to 1073 K at ambient pressure, Physics of the Earth and Planetary Interiors, Volume 161, Issues 1–2, 16 April 2007, Pages 1-12, ISSN 0031-9201, 10.1016/j.pepi.2006.11.002.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37307
Deposited On:05 Mar 2013 23:46
Last Modified:09 Nov 2021 23:28

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