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

Brodholt, J., Rushmer, T., Yuen, D., Petford, N. and Stackhouse, S., 2005. Shear-induced material transfer across the core-mantle boundary aided by the post-perovskite phase transition. Earth Planets Space, 57, pp. 459-464.

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Official URL: http://www.terrapub.co.jp/journals/EPS/pdf/2005/57...

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 <10 6 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.

Item Type:Article
ISSN:1343-8832
Subjects:Science > Earth Sciences
Group:University Executive Team
ID Code:905
Deposited By:INVALID USER
Deposited On:04 Apr 2007
Last Modified:07 Mar 2013 14:35

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