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

Nick Petford, Dave Yuen, Tracy Rushmer, John Brodholt, Stephen Stackhouse

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

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.)

Original languageEnglish (US)
Pages (from-to)459-464
Number of pages6
JournalEarth, Planets and Space
Volume57
Issue number5
DOIs
StatePublished - 2005

Bibliographical note

Funding Information:
Acknowledgments. We thank Curt Koenders, Renata M. Wentz-covitch and the ITR and CSEDI NSF programmes. Raymond Hide, Alan Brandon and an anonymous reviewer are thanked for helpful comments. NP thanks the University of Vermont for a visiting scholarship. TR thanks NASA (grant NAGS-10463) for supporting the deformation study of the Kernouve meteorite.

Keywords

  • Core metal transport
  • Deformation
  • Dilatancy
  • D″
  • Post-perovskite
  • Strain rate

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