Thermoelastic properties and crystal structure of MgSiO3 perovskite at lower mantle pressure and temperature conditions

A new synchrotron X‐ray diffraction study of MgSiO3 perovskite at high‐pressure and high‐temperature has been carried out in a laser‐heated diamond‐anvil cell to 94 GPa and temperatures above 2500 K. MgSiO3 perovskite is shown to be stable in this P–T range and adopts an orthorhombic structure (spac...

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Bibliographic Details
Published in:Geophysical research letters 2000-01, Vol.27 (1), p.21-24
Main Authors: Fiquet, G., Dewaele, A., Andrault, D., Kunz, M., Le Bihan, T.
Format: Article
Language:English
Subjects:
Crystalline rocks
Earth sciences
Earth, ocean, space
Exact sciences and technology
Experimental petrology
Internal geophysics
Sciences of the Universe
Solid-earth geophysics, tectonophysics, gravimetry
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Summary:A new synchrotron X‐ray diffraction study of MgSiO3 perovskite at high‐pressure and high‐temperature has been carried out in a laser‐heated diamond‐anvil cell to 94 GPa and temperatures above 2500 K. MgSiO3 perovskite is shown to be stable in this P–T range and adopts an orthorhombic structure (space group Pbnm), thus ruling out any phase transition or decomposition to an assemblage of denser oxides. Structural refinements show an increase of the orthorhombic distortion with increasing pressure, counterbalanced by a decrease of this distortion at high temperature, as evidenced by the Si‐O‐Si angle evolution. In addition, thermoelastic parameters identified from this new pressure‐volume‐temperature data set indicate that a significant amount of magnesiowüstite is required to match PREM bulk modulus profile, thus making a pure perovskite lower mantle unlikely.
ISSN:0094-8276
1944-8007
DOI:10.1029/1999GL008397