MgSiO3 postperovskite at D″ conditions

Renata M. Wentzcovitch, Taku Tsuchiya, Jun Tsuchiya

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Abstract

The postperovskite transition in MgSiO3 at conditions similar to those expected at the D″ discontinuity of Earth's lower mantle offers a paradigm for interpreting the properties of this region. Despite consistent experimental and theoretical predictions of this phase transformation, the complexity of the D″ region raises questions about its geophysical significance. Here we report the thermoelastic properties of Cmcm postperovskite at appropriate conditions and evidences of its presence in the lowermost mantle. These are (i) the jumps in shear and longitudinal velocities similar to those observed in certain places of the D″ discontinuity and (ii) the anticorrelation between shear and bulk velocity anomalies as detected within the D″ region. In addition, the increase in shear modulus across the phase transition provides a possible explanation for the reported discrepancy between the calculated shear modulus of postperovskite free aggregates and the seismological counterpart in the lowermost mantle.

Original languageEnglish (US)
Pages (from-to)543-546
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number3
DOIs
StatePublished - Jan 17 2006

Bibliographical note

Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.

Keywords

  • Core-mantle boundary
  • D″ layer
  • Earth's mantle
  • Elasticity

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