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Thermal versus elastic heterogeneity in high-resolution mantle circulation models with pyrolite composition: High plume excess temperatures in the lowermost mantle

Schuberth, B. S. A., H.-P. Bunge, G. Steinle-Neumann, C. Moder, and J. Oeser (2009), Thermal versus elastic heterogeneity in high-resolution mantle circulation models with pyrolite composition: High plume excess temperatures in the lowermost mantle, Geochem. Geophys. Geosyst., 10(1), Q01W01, doi:10.1029/2008GC002235.

Abstract
We study a new class of high-resolution mantle circulation models
and predict their corresponding elastic heterogeneity. Absolute temperatures are
converted to seismic velocities using published thermodynamically self-consistent
models of mantle mineralogy for a pyrolite composition. A grid spacing of $\sim$25 km
globally allows us to explore mantle flow at earth-like convective vigor so that
modeled temperature variations are consistent with the underlying mineralogy. We
concentrate on isochemical convection and the relative importance of internal and
bottom heating in order to isolate the thermal effects on elasticity. Models with a
large temperature contrast on the order of 1000 K across the core-mantle boundary,
corresponding to a substantial core heat loss of up to 12 TW, result in elastic
structures that agree well with tomography for a number of quantitative measures:
These include spectral power and histograms of heterogeneity as well as radial
profiles of root-mean-square amplitudes. In particular, high plume excess
temperatures of +1000--1500 K in the lowermost mantle lead to significant negative
anomalies of shear wave velocity of up to $-$4\%. These are comparable to strong
velocity reductions mapped by seismic tomography in the prominent low-velocity
regions of the lower mantle. We note that the inference of a large core heat flux is
supported by a number of geophysical studies arguing for a substantial core
contribution to the mantle energy budget. Additionally, we find significant
differences {\bf between the characteristics of thermal heterogeneity and the
characteristics of elastic heterogeneity} in the transition zone due to phase
transformations of upper mantle minerals. Our results underline the necessity to
include mineral physics information in the geodynamic interpretation of tomographic
models.
Further information
BibTeX
@article{id1348,
  author = {B. S. A. Schuberth and H.-P. Bunge and G. Steinle-Neumann and C. Moder and J. Oeser},
  journal = {Geochem. Geophys. Geosyst.},
  month = {jan},
  number = {1},
  title = {{Thermal versus elastic heterogeneity in high-resolution mantle circulation models with pyrolite composition: High plume excess temperatures in the lowermost mantle}},
  volume = {10},
  year = {2009},
  language = {en},
  url = {http://www.geophysik.uni-muenchen.de/~bernhard/downloads/Schuberth{\_}etal{\_}GC{\_}2009{\_}unedited.pdf},
  doi = {10.1029/2008GC002235},
  eid = {Q01W01},
}
EndNote
%0 Journal Article
%A Schuberth, B. S. A.
%A Bunge, H.-P.
%A Steinle-Neumann, G.
%A Moder, C.
%A Oeser, J.
%D 2009
%N 1
%V 10
%J Geochem. Geophys. Geosyst.
%T Thermal versus elastic heterogeneity in high-resolution mantle circulation models with pyrolite composition: High plume excess temperatures in the lowermost mantle
%U http://www.geophysik.uni-muenchen.de/~bernhard/downloads/Schuberth_etal_GC_2009_unedited.pdf
%8 jan
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