Elastic‐wave velocities of polycrystalline stishovite

Elastic-wave velocities of polycrystalline stishovite synthesized under high temperature and high pressure were measured at pressures up to 10 kb. Compressional- and shear-wave velocities were found to be 11.0 ± 0.2 and 5.50 ± 0.15 km/sec, respectively. The incompressibility from the measured elastic-wave velocities is K0 = 3.46 ± 0.24 Mb, which is consistent with the data from shock- and static-wave compressions. The composition of the lower mantle is discussed on the basis of the seismic-wave velocities and the densities of SiO2 (stishovite), MgO (periclase), and FeO (wustite). The mean atomic weight of the lower mantle is found to be 20.1–21.5.

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