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MgSiO3 postperovskite at D'' conditions.

ABSTRACT: The postperovskite transition in MgSiO(3) 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.

SUBMITTER: Wentzcovitch RM

PROVIDER: S-EPMC1334645 | biostudies-literature | 2006 Jan

REPOSITORIES: biostudies-literature

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MgSiO3 postperovskite at D'' conditions.

Wentzcovitch Renata M RM Tsuchiya Taku T Tsuchiya Jun J

Proceedings of the National Academy of Sciences of the United States of America 20060109 3

The postperovskite transition in MgSiO(3) 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 t ...[more]

PMID: 16407135

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