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Lattice thermal conductivity of lower mantle minerals and heat flux from Earth’s core

  1. Catherine A. McCammon
  1. Bayerisches Geoinstitut, Universit?t Bayreuth, D-95440 Bayreuth, Germany
  1. Edited by Mark H. Thiemens, University of California, La Jolla, CA, and approved September 9, 2011 (received for review June 30, 2011)

Abstract

The amount of heat flowing from Earth’s core critically determines the thermo-chemical evolution of both the core and the lower mantle. Consisting primarily of a polycrystalline aggregate of silicate perovskite and ferropericlase, the thermal boundary layer at the very base of Earth’s lower mantle regulates the heat flow from the core, so that the thermal conductivity (k) of these mineral phases controls the amount of heat entering the lowermost mantle. Here we report measurements of the lattice thermal conductivity of pure, Al-, and Fe-bearing MgSiO3 perovskite at 26?GPa up to 1,073?K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14?GPa up to 1,273?K. We find the incorporation of these elements in silicate perovskite and ferropericlase to result in a ~50% decrease of lattice thermal conductivity relative to the end member compositions. A model of thermal conductivity constrained from our results indicates that a peridotitic mantle would have k?=?9.1?±?1.2?W/m?K at the top of the thermal boundary layer and k?=?8.4?±?1.2?W/m?K at its base. These values translate into a heat flux of 11.0?±?1.4 terawatts (TW) from Earth’s core, a range of values consistent with a variety of geophysical estimates.

Footnotes

  • ?1To whom correspondence should be addressed. E-mail: Geeth.Manthilake{at}uni-bayreuth.de.
  • Author contributions: G.M.M., N.d.K., and D.J.F. designed research; G.M.M. performed research; G.M.M., N.d.K., and C.A.M. analyzed data; and G.M.M., N.d.K., D.J.F., and C.A.M. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1110594108/-/DCSupplemental.

Freely available online through the PNAS open access option.

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