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 journalArticle

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.) Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.
Original languageEnglish
Pages (from-to)459-464
Number of pages6
JournalEarth, Planets and Space
Volume57
Issue number5
DOIs
Publication statusPublished - 2005

Fingerprint

core-mantle boundary
perovskite
phase transition
outer core
mantle
metal
dilation
geomagnetism
shear modulus
downwelling
thermal conductivity
rheology
electrical conductivity
fluid flow
upwelling
scattering
wavelength
material
rate
science

Keywords

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

Cite this

Petford, Nick ; Yuen, Dave ; Rushmer, Tracy ; Brodholt, John ; Stackhouse, Stephen. / Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition. In: Earth, Planets and Space. 2005 ; Vol. 57, No. 5. pp. 459-464.
@article{58e965d4e6944b689e884d1de9c4488a,
title = "Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition",
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.) Copyright {\circledC} The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.",
keywords = "Core metal transport, Deformation, Dilatancy, D″, Post-perovskite, Strain rate",
author = "Nick Petford and Dave Yuen and Tracy Rushmer and John Brodholt and Stephen Stackhouse",
year = "2005",
doi = "10.1186/BF03351834",
language = "English",
volume = "57",
pages = "459--464",
journal = "Earth, Planets and Space",
issn = "1880-5981",
publisher = "SpringerOpen",
number = "5",

}

Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition. / Petford, Nick; Yuen, Dave; Rushmer, Tracy; Brodholt, John; Stackhouse, Stephen.

In: Earth, Planets and Space, Vol. 57, No. 5, 2005, p. 459-464.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition

AU - Petford, Nick

AU - Yuen, Dave

AU - Rushmer, Tracy

AU - Brodholt, John

AU - Stackhouse, Stephen

PY - 2005

Y1 - 2005

N2 - 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.) Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.

AB - 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.) Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.

KW - Core metal transport

KW - Deformation

KW - Dilatancy

KW - D″

KW - Post-perovskite

KW - Strain rate

UR - http://www.mendeley.com/research/shearinduced-material-transfer-across-coremantle-boundary-aided-postperovskite-phase-transition-1

U2 - 10.1186/BF03351834

DO - 10.1186/BF03351834

M3 - Article

VL - 57

SP - 459

EP - 464

JO - Earth, Planets and Space

JF - Earth, Planets and Space

SN - 1880-5981

IS - 5

ER -