Thermoelastic behaviour of silicate perovskites: Insights from new high-temperature ultrasonic data for ScAlO 3
Date
2008
Authors
Jackson, Ian
Kung, J
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
(Mg,Fe,Al)(Si,Al)O3 perovskite, stable only at pressures >20 GPa, is the dominant mineral of the Earth's lower mantle and thus controls its physical properties including seismic wave speeds. However, the development of a thorough understanding of the thermoelastic behaviour of this silicate perovskite is compromised by its marginal metastability on recovery at ambient conditions. Study of the close structural analogue ScAlO3, stable at much lower pressure, has the potential to provide insight into the behaviour of its silicate cousin. Here, previous exploratory ultrasonic measurements of the compressional and shear wave speeds on a fine-grained polycrystalline specimen have been extended to 1000 K under 300 MPa confining pressure within an internally heated gas-medium high-pressure apparatus. The wave speeds and derived bulk and shear moduli vary approximately linearly with temperature with derivatives (∂KS/∂T)P = -21.3(3) MPa K-1 and (∂G/∂T)P = -19.0(1) MPa K-1, respectively. The new data, along with previous measurements of thermal expansion and the pressure dependence of the elastic moduli, have been assimilated into the comprehensive internally consistent finite-strain model of thermoelastic behaviour proposed by [Stixrude, L., Lithgow-Bertelloni, C., 2005. Thermodynamics of mantle minerals-I. Physical properties. Geophys. J. Int. 162, 610-632]. Comparison of the newly constrained model for ScAlO3 with emerging data for MgSiO3 perovskite provides guidance in the analysis of the chemical composition and temperature of the Earth's lower mantle.
Description
Keywords
Keywords: Elastic moduli; Mineralogy; Pressure effects; Seismic waves; Shear waves; Silicate minerals; Thermal effects; Thermoelasticity; Ultrasonic measurement; Marginal metastability; Scandium aluminate; Silicate perovskite; Perovskite; chemical composition; conf Elasticity; Scandium aluminate; Silicate perovskite; Thermoelasticity
Citation
Collections
Source
Physics of the Earth and Planetary Interiors
Type
Journal article
Book Title
Entity type
Access Statement
License Rights
Restricted until
2037-12-31
Downloads
File
Description