Self-consistent Synthetic Mantle Discontinuities From Joint Modeling of Geodynamics and Mineral Physics and Their Effects on the 3D Global Wave Field

Seismic tomography is a powerful tool to aide plate reconstructions. Still its use has been hampered mainly because we don't understand very well how to interpret seismic images in terms of temperature and composition. Notable examples are observations of anti-correlation of bulk sound and shear velocity near the bottom of the mantle and a general lack of strong compressional heterogeneity in the lower mantle, both of which have given rise to a variety of speculations on lower mantle dynamics and its relation to past plate motion. Here we address this fundamental problem directly by employing a newly published, thermodynamically self consistent mantle mineralogy model, derived from considerations of Gibbs free energy minimisation of the mantle phase assemblage, which provides us with estimates of density and elastic constants for a wide range of lower mantle P,T conditions. We combine the model with simulations of global mantle circulation, where the very high numerical grid point resolution of less than 20 km throughout the mantle, amounting to more than 100 million grid points totally, is sufficient to achieve a vigorous regime of high Rayleigh number thermal convection that lies within the parameter range for which the mineralogic model was validated. We find a number of important results. For example, the hot spot flux is likely to exceed 10 TW, giving hot spots a more prominent role than is commonly believed. We also find that the anti-correlation of bulk sound and shear, and the low level of compressional wave speed arise naturally in our mineralogy/geodynamics simulations under the assumption of an isochemical mantle, greatly facilitating the interpretation of seismic heterogeneity in terms of past subduction. We will discuss these findings and explore their consequences for the development of next generation geodynamic earth models.

@inproceedings{id1681,
  author = {Schuberth, B. and Piazzoni, A. and Bunge, H. and Igel, H. and Steinle-Neumann, G. and Moder, C. and Oeser, J.},
  booktitle = {American Geophysical Union, Fall Meeting 2007, abstract \#U34A-04},
  language = {en},
  pages = {B9+},
  title = {Self-consistent Synthetic Mantle Discontinuities From Joint Modeling of Geodynamics and Mineral Physics and Their Effects on the 3D Global Wave Field},
  url = {http://adsabs.harvard.edu/abs/2007AGUFMDI51B..09S},
  year = {2007},
}

%O Conference Proceedings
%A Schuberth, B.
%A Piazzoni, A.
%A Bunge, H.
%A Igel, H.
%A Steinle-Neumann, G.
%A Moder, C.
%A Oeser, J.
%B American Geophysical Union, Fall Meeting 2007, abstract #U34A-04
%G en
%P B9+
%T Self-consistent Synthetic Mantle Discontinuities From Joint Modeling of Geodynamics and Mineral Physics and Their Effects on the 3D Global Wave Field
%U http://adsabs.harvard.edu/abs/2007AGUFMDI51B..09S
%D 2007