Low-Frequency Attenuation in Polycrystalline Silicates and Microstructurally Equilibrated Silicate Partial Melts

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9706213 Cooper The dynamic and quasistatic mechanical responses of carefully engineered aggregates of ferromagnesian olivine and of microstructurally equilibrated olivine + synthetic basalt partial melts will be evaluated as functions of temperature, frequency, grain size and loading morphology (Young's-modulus mode in compression and flexure, shear-modulus mode in torsion). The experiments emphasize (i) the use of drained conditions for the partial melts, (ii) the use of specific differential-stress and temperature potentials combined with a fine grain size such that a Newtonian rheology describes the crystalline phase in both partial melt and melt-free states, and (iii) a low-viscosity liquid phase in the partial melt experiments such that the compaction length exceeds the specimen size. The immediate goal of the research is to discriminate the effect(s) of partial melting on the dynamic signature of the aggregate from the intrinsic behavior associated with the dissipation of energy by solid-state grain-boundary processes. Given the experimental parameters to be explored, extrapolation of the results to upper-mantle conditions is possible. The longer-range goal of the research is to initiate evaluation of melt-segregation microstructures ("mesostructures") on the dynamic response. ***