Physical Properties at High Pressure and Temperature: Implications for Mantle Stratification and Dynamics

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Knowledge of the high pressure and high temperature behavior of key physical properties of minerals is an essential ingredient in the continuing effort to understand convection within Earth's mantle. Since much of our current understanding is still based on assumed and extrapolated elastic and thermal properties of silicate minerals, it remains difficult to determine whether or not radial seismic models for the mantle imply chemical stratification. The PI has constructed a laboratory for the measurement at high pressure and temperature of key physical properties of candidate mantle constituents. Laser-Induced Phonon Spectroscopy has been coupled with diamond anvil cell technology to measure elastic constants and thermal diffusivity of minerals at high pressure. Results for olivine to 7 GPa have recently been reported. Extension of such measurements on a variety of minerals to a transition zone and lower mantle pressure regime (12 to 25 GPA) is a principle goals of the present work. Measurements at simultaneous high temperature and pressure will be attempted.