An Interdisciplinary Approach for Inferring the Thermochemical Structure of the Upper Mantle
Abstract
In order to our knowledge of the thermochemical structure of the upper mantle, we use an interdisciplinary approach which involves seismic and density data and uses current knowledge of material properties at high pressure and temperature. We consider a reference mineral physics model based on current knowledge of material properties at high pressure (P) and temperature (T). The phase equilibria and the elastic properties are computed with a recent thermodynamical model covering a six oxides (NCFMAS) system. Anelastic properties are implemented with a P, T and frequency dependent law based on mineral physics knowledge. Viscosity is also evaluated with a similar physical law. The model predicts values of physical parameters (e.g., shear velocity, density, viscosity) as function of pressure (or depth), temperature and composition. Equilibrium compositions or mixtures of different compositions (e.g., MORB and Harzburgite) can be considered. Starting from this model, we interpret available global seismic models in terms of T by assuming different C structures. We also use extreme physical laws for the most uncertain material parameters, i.e. viscosity and anelasticity. For each model, we predict density and viscosity structure. Then, we compute the synthetic geoid from instantaneous flow calculations by using the STAGYY code [Tackley, PEPI 2008] and the misfits with observations. The analysis of the results will give a robust interpretation of the thermochemical structure of the upper mantle, will reduce the trade-off between T and C and it will point out possible problems with uncertain physical properties in the reference mineral physics model used.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.U23D0076T
- Keywords:
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- 8124 TECTONOPHYSICS / Earth's interior: composition and state;
- 7208 SEISMOLOGY / Mantle