HR: 0800h
AN: MR31A-0115    [Abstracts]
TI: Elastic wave velocities of Fe-bearing ringwoodite under pressure and temperature conditions of the mantle transition region
AU: * Higo, Y
EM: higo@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho,Matsuyama 790-8577,Japan , Matsuyama, 790-8577 Japan
AU: Inoue, T
EM: inoue@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho,Matsuyama 790-8577,Japan , Matsuyama, 790-8577 Japan
AU: Irifune, T
EM: irifune@dpc.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho,Matsuyama 790-8577,Japan , Matsuyama, 790-8577 Japan
AU: Li, B
EM: bli@notes.cc.sunysb.edu
AF: Mineral Physics Institute, State University of New York, Stony Brook, NY 11794, New York, 11794 United States
AU: Liebermann, R C
EM: Robert.Liebermann@stonybrook.edu
AF: Mineral Physics Institute, State University of New York, Stony Brook, NY 11794, New York, 11794 United States
AB: Ringwoodite (high pressure polymorph of olivine) is considered to be the most abundant mineral at depths between 520km and 660km in the mantle transition region, and it is important to accurately determine the elastic wave velocities in order to discuss the mineralogy and composition of the mantle transition region. In this study, We have developed ultrasonic interferometry conjunction with in situ X-radiation techniques (X-ray diffraction and X-radiography) in a DIA-type cubic anvil high-pressure apparatus, in order to obtain high-quality elastic wave velocity data under the conditions of the mantle transition region and measured the elastic wave velocity of iron-bearing ringwoodite under high temperature and high pressure. The specimen was hot-pressed at 19GPa and 1473K in a 3000-ton high pressure apparatus (ORANGE-3000: GRC at ehime university). High-pressure ultrasonic experiments were performed using Kawai-type high-pressure apparatus SPEED-1500 at BL04B1. The unit cell constants of pressure marker (NaCl, Au) and sample (ringwoodite) were measured for estimation of pressure and sample length. Also, X-radiography was used in this study for direct measurement of sample length at high pressure and high temperature. The ultrasonic signals were generated and received by a LiNbO₃ transducer (10° Y-cut), which can produce both longitudinal and shear waves at the same time. The waveforms were very clear and the each echoes both P-wave and S-wave were identifiable at high temperature and high pressure. P-wave and S-wave velocities increasing with increasing pressure. And P-wave and S-wave velocities decrease with increasing temperature. Especially, S-wave velocity has large temperature dependence, which velocity (at 18 GPa, 1673 K) slower than those of ambient condition. The results of our high-pressure experiment, including the elastic moduli and their pressure dependence, effect of iron on the elastic moduli, as well as their implication for the mantle transition zone, will be presented.
DE: 3909 Elasticity and anelasticity
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005