HR: 11:20h
AN: V32B-05    [Abstracts]
TI: Towards driving mantle convection by mineral physics
AU: * Piazzoni, A S
EM: antonio.piazzoni@geophysik.uni-muenchen.de
AF: Department of Earth and Environmental Sciences Geophysics Munich University, Theresienstr. 41 80333 Munich Germany, Muenchen, 80333 Germany
AU: Bunge, H
EM: hans-peter.bunge@geophysik.uni-muenchen.de
AF: Department of Earth and Environmental Sciences Geophysics Munich University, Theresienstr. 41 80333 Munich Germany, Muenchen, 80333 Germany
AU: Steinle-Neumann, G
EM: g.steinle-neumann@uni-bayreuth.de
AF: Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, 95440 Germany
AB: Models of mantle convection have become increasingly sophisticated over the past decade, accounting, for example, for 3 D spherical geometry, and changes in mantle rheology due to variations in temperature and stress. In light of such advances it is surprising that growing constraints on mantle structure derived from mineral physics have not yet been fully brought to bear on mantle convection models. In fact, despite much progress in our understanding of mantle mineralogy a partial description of the equation of state is often used to relate density changes to pressure and temperature alone, without taking into account compositional and mineralogical models of the mantle. Similarly, for phase transitions an incomplete description of thermodynamic constraints is often used, resulting in significant uncertainties in model behavior. While a number of thermodynamic models (some with limited scope) have been constructed recently, some lack the rigor in thermodynamics - for example with respect to the treatment of solid solution - that is needed to make predictions about mantle structure. Here we have constructed a new thermodynamic database for the mantle and have coupled the resulting density dynamically with mantle convection models. The database is build on a self-consistent Gibb's free energy minimization of the system MgO-FeO-SiO2-CaO-Al2O3 that is appropriate for standard (dry) chemical models of the Earth's mantle for relevant high pressure and temperature phases. We have interfaced the database with a high-resolution 2-D convection code (2DTERRA), dynamically coupling the thermodynamic model (density) with the conservation equations of mantle flow. The coupled model is run for different parameterizations of viscosity, initial temperature conditions, and varying the internal vs. external heating. We compare the resulting flow and temperature fields to cases with the Boussinesq approximation and other classical descriptions of the equation of state in mantle dynamics to assess the influence of realistic mineralogical density on mantle convection.
DE: 1025 Composition of the mantle
DE: 3939 Physical thermodynamics
DE: 3999 General or miscellaneous
DE: 4465 Phase transitions
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005