HR: 17:55h
AN: T24A-08    [Abstracts]
TI: In Search of the Mixed Derivative \partial$^{2}$M/\partial${P}\partial${T} (M = G, K): Joint Analysis of Ultrasonic Data for Polycrystalline Pyrope From gas- and Solid-Medium Apparatus
AU: * Gwanmesia, G D
EM: ggwanmes@desu.edu
AF: Delaware State University, Department of Physics & Pre-Engineering, Dover, DE 19901 United States
AU: Jackson, I
EM: Ian.jackson@anu.edu.au
AF: Australian National University, Research School of Earth Sciences, Canberra, ACT-0200 Australia
AU: Liebermann, R C
EM: Robert.liebermann@stonybrook.edu
AF: State University of New York, Department of Geosciences, Stony Brook, NY 11794-2100 United States
AB: Robust extrapolation of laboratory-derived elasticity data to the conditions of the deep mantle requires knowledge/assumptions about \partial$^{2}$M/\partial${P}\partial${T}- so far the subject of very few experimental studies. Accordingly, we have begun to explore the circumstances under which constraints on these mixed derivatives might be extracted from joint analysis of data obtained by high-temperature ultrasonic interferometry on fine-grained polycrystals in gas- and solid-medium high-pressure apparatus. In a first case study, elastic wave velocities have been newly measured on dense isotropic polycrystalline Mg$_{3}$Al$_{2}$Si$_{3}$O$_{12}$ to 1000 K and 300 MPa in an internally heated gas-medium high-pressure apparatus for comparison with the results of a previous study in multi-anvil apparatus {\it (Gwanmesia et al., submitted)}. For this study dense fine-grained polycrystals were prepared by hot pressing within a 2000-ton uniaxial split-sphere apparatus at 10 GPa and 1275 K for 1 hour, from a homogeneous glass starting material. The physical properties of the recovered specimens have been characterized with density measurements, x-ray diffraction and scanning electron microscopy (SEM). The measured elastic compressional and shear wave velocities determined are in excellent agreement with the temperature-dependent Hashin-Shrikman averages calculated from single-crystal elasticity data. Progress in the analysis of the combined gas- and solid-medium M (P, T) dataset for (\partial${M}/\partial${P})$_{T}, (\partial${M}/\partial${T})$_{P} ${and} \partial$^{2}$M/\partial${P}\partial${T} will be reported.
DE: 3909 Elasticity and anelasticity
DE: 3924 High-pressure behavior
DE: 3994 Instruments and techniques
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting