Abstract
Ultrasonic shear wave velocities of polycrystalline Fe2SiO4 olivine and spinel were measured at pressures of up to 5.2GPa and temperatures of up to 700°C using a wedge-type cubic anvil apparatus. Pressure derivative of shear wave velocity at room temperature was determined as (∂Vs/∂P)=3.8 (km/sec/100GPa) for Fe2SiO4 olivine and (∂Vs/∂P)=1.7(km/sec/100GPa) for Fe2SiO4 spinel. Shear wave velocity jump amounting to 11% was observed at a run with Fe2SiO4 olivine as a starting material at 5.2 GPa and at around 650°C. X-ray diffraction analysis on the recovered sample indicates that the sudden increase in shear wave velocity is associated with the olivine-spinel transformation. About 60% completion of the transformation was observed in the particular run. No anomalous decrease in shear wave velocity was detected at the transformation.
