HR: 10:50h
AN: MR52A-03 INVITED    [Abstracts]
TI: Sound velocities of mantle and subducted slab lithologies: Constraints from combined in situ X-ray and ultrasonic measurements
AU: * Irifune, T
EM: irifune@dpc.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime Univ., 2-5 Bunkyo-cho, Matsuyama, 790-8577, Japan
AU: Higo, Y
EM: higo@spring8.or.jp
AF: Japan Synchrotron Radiation Research Institute, 1-1-1 Koto, Mikazuki-cho, Sayo-gun, 679- 5198, Japan
AU: Kono, Y
EM: kono@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime Univ., 2-5 Bunkyo-cho, Matsuyama, 790-8577, Japan
AU: Inoue, T
EM: inoue@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime Univ., 2-5 Bunkyo-cho, Matsuyama, 790-8577, Japan
AU: Funakoshi, K
EM: funakosi@spring8.or.jp
AF: Japan Synchrotron Radiation Research Institute, 1-1-1 Koto, Mikazuki-cho, Sayo-gun, 679- 5198, Japan
AB: We have developed techniques to precisely measure the sound velocities of high-pressure phases at pressures to 22 GPa and temperatures to 1800K using a combination of synchrotron in situ X-ray and ultrasonic measurements with a Kawai-type multianvil apparatus. Using these techniques, we measured the sound velocities of ringwoodite and majorite in a pyrolite composition , as well as those of MORB in the garnetite facies (majorite + minor stishovite). We found quite strong non-linear decreases of Vp and Vs with temperature, particularly for Vs in majorite, under these P, T conditions of the mantle transition region (MTR). Our results suggest that pyrolite yields seismic velocities consistent with typical seismological models for the MTR, except for the bottom part of this region, whereas piclogite or basalt compositions may lead to velocities substantially lower than those seismologically derived. In contrast, harzburgite would better fit to the seismological models in the lower half of the mantle transition region, provided that the geotherm in this region is of adiabatic, which may be due to accumulation of main bodies of stagnant slabs (depleted peridotite or harzburgite) near the 660 km discontinuity.
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 3994 Instruments and techniques
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting