Geodynamic models with thermodynamically self-consistent mineral physics

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We propose to combine geodynamic mantle modeling with thermodynamic models of mantle mineralogy in order to gain a better understanding of the thermal and elastic structure of Earth s mantle. For the geodynamic modeling we will use two dimensional (2-D) and three dimensional (3-D) mantle convection codes. For the thermodynamic mantle model we will apply the Gibbs-free-energy minimization method in order to compute mantle phase equilibria for a range of chemical mantle models. (1) temperature fields from mantle convection modeling will be postprocessed: we will assign to each Temperature (T) and Pressure (P) grid point value from the convection calculation its corresponding equilibrium mineral assemblage and physical properties. (2) We will then couple the convection and mineralogical model: we will use the density of the mineral assemblage to compute buoyancy forces (via the buoyancy term in the momentum equation) in the convection model. Thus densities derived from the mineralogical model establish convective flow and a thermal structure in the geodynamic model, while at the same time the P, T structure of the convection model is used in the computation of the equilibrium mineral assemblage. By combining the equation-of-state parameters with a shear wave model we will be able to study convection consistently with the underlying mineralogy. The proposed work will permit us to compare predictions of geodynamic mantle models directly to observed seismic properties. This is important because recent seismic studies of the mantle show results that are not easily understood in terms whole mantle convection. We will test the hypothesis that the seismic results can be attributed in part to complexities in the mineralogy. The mineralogical model will be made available for general use through a website, as a research and teaching tool for the geophysical and high pressure mineralogical community.