Cordilleran Section - 113th Annual Meeting - 2017

Paper No. 24-1
Presentation Time: 8:35 AM

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


ZHANG, Jin, Department of Earth and Planetary Sciences and Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131 and BASS, Jay D., Geology, COMPRES, and University of Illinois Urbana-Champaign, 1301 West Green St, Urbana, IL 61822, jinzhang@unm.edu

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.