ELASTICITY CHANGE ACROSS THE OLIVINE-WADSLEYITE TRANSITION AND ITS IMPLICATIONS FOR THE COMPOSITION AND DYNAMICS NEAR THE 410 DISCONTINUITY

Single-crystal elasticity of Fe-bearing olivine has been measured up to the pressure temperature conditions close to those at 410 km depth in the Earth’s interior. Combining with previous single-crystal sound velocity measurements of olivine with similar composition, a best-fit thermal elastic model of olivine can be inverted. Velocity jump across the olivine-wadsleyite transition can thus be calculated from the obtained thermal elastic models. We found that a large lateral variation in composition near the 410 km discontinuity is required to explain the observed differences between different regional seismic models. Based on the obtained single-crystal elasticity model, elastic anisotropy of olivine is predicted to slightly decrease with depth, still remains to be high at 410 km depth. Assuming a pyrolitic mantle composition, we expect a large anisotropy decrease across the 410 discontinuity if mantle flow existed in the adjacent regions.