HR: 08:45h
AN: T31B-04    [PDF]
TI: Estimate of the Temperature Field of the Mantle and its Contribution to the Lateral Heterogeneity of the Earth's Interior
AU: * Paine, J H
EM: painej@eps.berkeley.edu
AF: Dept. of Earth and Planetary Science, University of California - Berkeley, 340 McCone Hall, Berkeley, CA 94720-4768
AU: Lithgow-Bertelloni, C R
EM: crlb@umich.edu
AF: Geological Sciences, University of Michigan, 2534 C.C. Little Building 425 E. University Ave., Ann Arbor, MI 48109
AU: Stixrude, L P
EM: stixrude@umich.edu
AF: Geological Sciences, University of Michigan, 2534 C.C. Little Building 425 E. University Ave., Ann Arbor, MI 48109
AB: The origin of lateral heterogeneity is important for understanding many aspects of the Earth's interior, including mantle flow and viscosity structure, the gravity field, and dynamic topography at the surface. These lateral variations can be ascribed to three main causes: temperature, bulk composition, and phase assemblage. Modeling the temperature field is an important step in understanding the relative contributions of these variations. Down-welling slabs are the most important source of density heterogeneity in the mantle. We assume the temperature field to be largely the product of subduction and neglect the contributions due to active upwellings. We use a model of the history of subduction for the last $\sim$120 Myr to derive a density field for the mantle, from which we compute a three-dimensional velocity field by solving Stokes equation for an incompressible Newtonian fluid. Using a commercial finite-element software package called Abaqus we solve for the temperature field by solving the advection-diffusion equation in steady state. We choose free-slip, 3000 K velocity-temperature boundary conditions at the core-mantle boundary, and at the surface we constrain velocities to be plate velocities and temperatures to be 300 K. We recover the half-space cooling behavior in the lithosphere and obtain reasonable values of the heat flow, indicating that our predicted temperature field behaves as expected. We use our predicted temperature fields to compute the expected phase assemblage for a mantle of constant bulk composition. We will focus our discussion on the expected topography on major seismic discontinuities (410 and 660) and comparisons to three-dimensional seismological observations.
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 7207 Core and mantle
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8180 Tomography
SC: Tectonophysics [T]
MN: 2003 Fall Meeting