HR: 1340h
AN: T43B-1323    [Abstracts]
TI: Thermal Conductivity of Complex Materials at High Temperatures and Pressures
AU: * Brown, J M
EM: brown@ess.washington.edu
AF: Earth and Space Sciences, University of Washington Box 351310, Seattle, WA 98195 United States
AU: Xu, Y
EM: yousheng.xu@yale.edu
AF: Geology and Geophysics, Yale University, New Haven, CT 06520 United States
AU: Harrell, M
EM: mharrell@ess.washington.edu
AF: Earth and Space Sciences, University of Washington Box 351310, Seattle, WA 98195 United States
AU: Shankland, T J
EM: shanklan@lanl.gov
AF: Geophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 United States
AB: Measurements of lattice thermal diffusivity have been obtained on (Mg$_{0.9}$Fe$_{0.1}$)$_{2}$SiO$_{4}$ olivine, its high-pressure polymorphs, and of (Mg$_{0.9}$Fe$_{0.1}$)SiO$_{3}$ enstatite at conditions of temperature and pressure. We used two independent techniques: Impulsive Stimulated Light Scattering to 5 GPa and 1273 K and the $\AA$ngstr\"{o}m method on cylindrical samples in a multianvil apparatus to 20 GPa and 1373 K. Lattice thermal conductivities were calculated from heat capacities and equations of state. Conductivities are consistent with previous results obtained at 1 atm. In olivines conductivity increases at each phase transition from olivine to spinel structures (corresponding to velocity discontinuities at depths of 410 and 520 km in the Earth). Of greatest significance is the fact that for each of these phases, lattice conductivity closely follows a T$^{-1/2}$ dependence on temperature T, a prediction of Klemens (1960) for materials containing abundant lattice defects. If such a dependence applies to other silicates and complex crystals, there should be a useful way to estimate conductivities at high temperatures from room temperature measurements.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8130 Heat generation and transport
DE: 5134 Thermal properties
DE: 5139 Transport properties
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting