HR: 1330h
AN: V42A-0318    [PDF]
TI: Partitioning of H$_{2}$O on high pressure phase transformation of olivine
AU: * Inoue, T
EM: inoue@sci.ehime-u.ac.jp
AF: Ehime University, Bunkyo-cho 2-5, Matsuyama, 790-8577 Japan
AU: Wada, T
AF: Ehime University, Bunkyo-cho 2-5, Matsuyama, 790-8577 Japan
AU: Sasaki, R
AF: Ehime University, Bunkyo-cho 2-5, Matsuyama, 790-8577 Japan
AU: Irifune, T
EM: irifune@dpc.ehime-u.ac.jp
AF: Ehime University, Bunkyo-cho 2-5, Matsuyama, 790-8577 Japan
AU: Yurimoto, H
EM: yuri@geo.titech.ac.jp
AF: Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo, 152-8551 Japan
AB: Water is the most abundant volatile component on the Earth's surface, and it has been supplied to the Earth's interiors by subducted slab. Water influences the physical properties and melting temperature of minerals. Olivine is the most abundant mineral in the mantle, and it is clarified that the high-pressure polymorphs of olivine, wadsleyite and ringwoodite, can contain 3wt% of H$_{2}$O in their crystal structures (e.g. Inoue et al., 1995, 1998). However, the partitioning of H$_{2}$O among these minerals has not been clarified yet except for olivine-wadsleyite transformation (Chen et al., 2003). We have determined the partitioning of H$_{2}$O between wadsleyite and ringwoodite and between ringwoodite and perovskite, and clarified the distribution of H$_{2}$O among upper mantle, mantle transition zone and lower mantle. High-pressure experiments were conducted by MA-8 type (Kawai-type) high-pressure apparatus in Ehime University, and the chemical compositions were determined by EPMA. The water contents of minerals were measured by SIMS in Tokyo Institute of Technology. We succeeded to synthesize large (approximately 50 $\mu$m) coexisting crystals of wadsleyite and ringwoodite, and of ringwoodite and perovskite, and we could clarify the partitioning of H$_{2}$O between those coexisting minerals. The partition coefficients between wadsleyite and ringwoodite and between ringwoodite and perovskite were about 2 and about 10 or more, respectively. We (Chen et al., 2003) have already determined that the partition coefficients between wadsleyite and olivine is about 5, so the partitioning among upper mantle, 410-520km and 520-660km of mantle transition zone, and lower mantle are 4:20:10:1. Thus the mantle transition zone should be a strong water reservoir in the Earth's interiors.
DE: 1025 Composition of the mantle
DE: 1212 Earth's interior--composition and state (8105)
DE: 1645 Solid Earth
DE: 3630 Experimental mineralogy and petrology
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting