Discontinuous evolution of single-crystal elastic constants as a function of pressure through the C2/c <-> P2(1)/c phase transition in spodumene (LiAlSi2O6)

Sondergeld, P. and Li, B. S. and Schreuer, J. and Carpenter, M. A. (2006) Discontinuous evolution of single-crystal elastic constants as a function of pressure through the C2/c <-> P2(1)/c phase transition in spodumene (LiAlSi2O6). Journal of Geophysical Research-Solid Earth, 111 (B7). Art. no. B07202. DOI 10.1029/2005JB004098

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Official URL: http://dx.doi.org/10.1029/2005JB004098

Abstract

A Landau free energy expansion in one order parameter has been developed to describe the first-order C2/c ↔ P21/c phase transition at high pressures in spodumene (LiAlSi2O6). The complete set of elastic constants required for this model was determined at ambient conditions by resonant ultrasound spectroscopy. Other coefficients in the 246 expansion were calibrated using lattice parameter data from the literature, which had been collected by following the transition in a diamond anvil cell. The complete calibration leads to predictions of significant, abrupt changes in elastic constants at the transition point, 3.19 GPa, which have then been tested against ultrasonic data obtained in situ at high pressures in a uniaxial split cylinder apparatus. Velocities of compressional waves in three mutually perpendicular directions through single crystals of spodumene were measured and used to extract elastic constant data. The transition, indeed, causes large, abrupt changes of single-crystal elastic constants with increasing pressure. Steep increases in attenuation were also observed in the vicinity of the transition point for two directions and over a broader pressure interval in the third direction. The Landau expansion reproduces the general form of the elastic anomalies, even though it does not do as well for spontaneous strain variations. If this type of transition occurred in mantle pyroxenes (or in any other mantle phase), it would be expected to leave a distinctive signature in seismic velocity profiles of the Earth's interior.

Item Type: Article
Additional Information: Copyright 2006 by the American Geophysical Union.
Uncontrolled Keywords: 2006 AREP; IA51; 2006 P
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
08 - Green Open Access
Journal or Publication Title: Journal of Geophysical Research-Solid Earth
Volume: 111
Page Range: Art. no. B07202
Identification Number: 10.1029/2005JB004098
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:03
Last Modified: 10 Jul 2014 11:59
URI: http://eprints.esc.cam.ac.uk/id/eprint/702

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