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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)

  1. Fig. 1.

    Measured lattice thermal conductivities for the respective mineral compositions considered (see SI Appendix for more detail). We use the values determined from the amplitude ratio (Θ), in order to minimize contributions from direct radiative transfer. Solid lines indicate the fits of Eq.?1, using the parameters reported in Table?1.

  2. Fig. 2.

    Thermal conductivity of MgO periclase at ambient pressure, extrapolated from our high pressure measurements using Eq.?2 and our thermodynamic model. Values compare well at high temperatures with the measurements of Touloukian, et al. (25) for polycrystalline MgO, though it falls somewhat below those of Kanamori, et al. (26) and Katsura (12). The model underestimates the lowest T values, as does a simple 1/T relation.

  3. Fig. 3.

    Thermal conductivity models computed from our results using Hashin-Shtrikman averaging (28) for aggregates of 20%?Pe?+?80%?Pv (top) and 20%?PeFe20?+?80%?PvFe03 (bottom). The mantle geotherm is constructed by combining a 1,600?K pyrolite adiabat (29) with a superadiabatic temperature increase in the bottom 200?km through the thermal boundary layer to reach the range of temperature estimates for the core-mantle boundary (30, 31). Temperatures in the thermal boundary layer thus increase from 2,600?±?200?K at its top to Graphic at the CMB.

  4. Fig. 4.

    CMB heat flux as a function of the temperature contrast across the D’’, for different thermal boundary layer thicknesses, computed from our model values for the lower-most mantle by iteratively adjusting the thermal profile for steady state. Solid envelopes represent a 20%?PeFe20?+?80%?PvFe03 assemblage, accounting for uncertainty on the k values. Dashed lines indicate the positions of these envelopes if the silicate component of the thermal boundary layer was in the postperovskite (PPv) phase for T?<?3,300?K, assuming kPPv?=?2?×?kPv (37). Independent core-mantle boundary heat flux values based on mantle plume buoyancy flux estimates are shown for comparison (see ref.?2).

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