Elastic moduli of wadsleyite (beta-Mg2SiO4) to 7 gigapascals and 873 kelvin
Simultaneous sound velocity measurements and x-ray diffraction studies were made on wadsleyite (beta-Mg2SiO4) to 7 gigapascals and 873 kelvin. The calculated adiabatic bulk (K) and shear (G) moduli yield K (at room conditions) = 172(2) gigapascals, dK/dP = 4.2(1), and dK/dT = -0.012(1) gigapascals per kelvin, and G (at room conditions) = 113(1) gigapascals, dG/dP = 1.5(1), and dG/dT = -0. 017(1) gigapascals per kelvin, respectively. The data imply that the P and S wave velocity contrasts between olivine and wadsleyite require an olivine amount of 38 to 39 percent in the upper mantle to satisfy the observed 410-kilometer discontinuity, but 55 to 60 percent to account for the velocity increase through the transition zone.
B. Li, Center for High Pressure Research and Mineral Physics Institute, State University of New York, Stony Brook, NY 11794-2100, USA. R. C. Liebermann and D. J. Weidner, Center for High Pressure Research and Department of Geosciences, State.
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