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Volume 57 Supplement 5

Special Issue: Special Section for the 2004 Mid-Niigata Prefecture Earthquake (1)

Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition

Earth, Planets and Space volume 57, pages 459–464 (2005)Cite this article

Abstract

We present a novel mechanical model for the extraction of outer core material upwards across the CMB into the mantle side region of D” and subsequent interaction with the post-perovskite (ppv) phase transition. A strong requirement of the model is that the D” region behaves as a poro-viscoelastic granular material with dilatant properties. Using new ab-initio estimates of the ppv shear modulus, we show how shear-enhanced dilation promoted by downwelling mantle sets up an instability that drives local fluid flow. If loading rates locally exceed c. 10−12 s−1, calculated core metal upwelling rates are >10−4 m/s, far in excess of previous estimates based on static percolation or capillary flow. Associated mass flux rates are sufficient to deliver 0.5% outer core mass to D” in < 106 yr, provided the minimum required loading rate is maintained. Core metal transported upwards into D” may cause local rapid changes in electrical and thermal conductivity and rheology that if preserved, may account for some of the observed small wavelength heterogeneties (e.g. PKP scattering) there.

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Authors and Affiliations

  1. Center for Earth and Environmental Science Research, Kingston University, Surrey, KT1 2EE, UK

    Nick Petford

  2. Minnesota Supercomputer Institute, University of Minnesota, Minneapolis, MN55455, USA

    Dave Yuen

  3. Department of Geology, University of Vermont, Burlington, Vermont, 04505, USA

    Tracy Rushmer

  4. Department of Earth Sciences, University College London, WC1E 6BT, UK

    John Brodholt & Stephen Stackhouse

Authors
  1. Nick Petford
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  2. Dave Yuen
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  3. Tracy Rushmer
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  4. John Brodholt
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  5. Stephen Stackhouse
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Correspondence to Nick Petford.

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Petford, N., Yuen, D., Rushmer, T. et al. Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition. Earth Planet Sp 57, 459–464 (2005). https://doi.org/10.1186/BF03351834

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  • DOI: https://doi.org/10.1186/BF03351834

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