2021 Fiscal Year Annual Research Report
高圧実験と地震波観測による統合的アプローチを用いた沈み込み帯下の構造と進化の解明
| Project/Area Number |
19H02002
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| Research Institution | Ehime University |
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Principal Investigator |
GREAUX Steeve 愛媛大学, 地球深部ダイナミクス研究センター, 助教 (90543166)
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| Co-Investigator(Kenkyū-buntansha) |
河合 研志 東京大学, 大学院理学系研究科(理学部), 准教授 (20432007)
肥後 祐司 公益財団法人高輝度光科学研究センター, 回折・散乱推進室, 主幹研究員 (10423435)
佐藤 友彦 東京工業大学, 理学院, 研究員 (80714831)
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | mantle composition / high pressure / ultrasonic measurement / seismological model / triplication |
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| Outline of Annual Research Achievements |
P- and S-wave velocities (VP and VS) are the unique tool we have to explore the inaccessible deep Earth and planetary interiors via comparisons with the observed seismic velocities. In this FY we carried out additional VP and VS measurements of MORB composition as well as Martian peridotite in the framework of an international collaboration with the Institut de Mineralogie et Physique des Materiaux Condenses (IMPMC, France). We also conducted sound velocity measurements on partially molten Olivine + FeS samples, which were meant to test the feasibility of such measurements for the partial melting of hydrated MORB components in a pyrolitic mantle. All sound velocity measurements on the rock aggregates were carried out by in situ ultrasonic interferometry, X-ray radiography and diffraction techniques, at high P and T in the multianvil press at the beamline Bl04B1 located at the synchrotron facility SPring-8.
Analyses of the MORB, pyrolite and harzburgite data collected in the previous FY are now underway, and several papers are in preparation. Preliminary results from the partial melting experiments suggest the VS/VP primarily depends on the micro-texture of the silicate matrix that contains the melt rather the composition of the melt itself, although the latter might play a role in controlling the mobility of the melt in the silicate matrix. Our results suggest harzburgitic composition can explain high shear seismic velocities observed above the 660, while MORB and/or partial melt are necessary to explain the low velocities beneath the 660.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In this FY, we completed our experimental datasets on MORB, pyrolite and harzburgite compositions, which will permit precise estimates of the seismic velocities of the subducted slab up to ~25 GPa, which corresponds to the depths of the uppermost lower mantle. The results are to be compared with local seismic models established by triplication methods. This plan is however still delayed due to pandemic issues and the difficulties to effectively work with our seismologist's team in Tokyo. We however recently noted some improvement, and had one meeting in Ehime in March 2022, which will be followed by another meeting in Tokyo in June 2022.
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| Strategy for Future Research Activity |
In the next FY, we plan to put emphasis on curating and summarizing our data on MORB, pyrolite and harzburgite throughout more effective work with our seismologist team. The obtained velocity data and mineralogical models will be compared to local seismic models derived from the triplication methods developed by our seismological team. The combined velocity data and local seismological models will provide improved knowledge on the structure of the mantle in various subducted slab regions across the globe.
In addition, we plan to continue our partial melting experiments. We already obtained beamtime to carry out such experiments on lunar rock, Martian peridotite and pyrolite + MORB. The pyrolite + MORB project, addresses directly the questions raised in the current application. The lunar and Martian projects aims at carrying out our expertise to the study of planetary interiors in the framework of
a JSPS post-doc project started from April 2022, and consolidating our international collaboration with the IMPMC, respectively.
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[Journal Article] Low Velocity Zones in the Martian Upper Mantle Highlighted by Sound Velocity Measurements2021
Author(s)
Xu F., Siersch N.C., Greaux S., Rivoldini A., Kuwahara H., Kondo N., Menguy N., Kono Y., Higo Y., Plesa A.-C., Badro J. and Antonangeli D.
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Journal Title
Geophysical Research Letters
Volume: 48(19)
Pages: e2021GL093977
DOI
Peer Reviewed / Int'l Joint Research
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[Presentation] Low Velocity Zones in the Martian Upper Mantle Highlighted by Sound Velocity Measurements2022
Author(s)
Xu F., Siersch N., Greaux S., Rivoldini A., Kuwahara H., Kondo N., Wehr N., Menguy N., Kono Y., Higo Y., Plesa A.-C., Badro J. and Antonangeli D.
Organizer
23rd General Meeting of the International Mineralogical Association, IMA 2022, Lyon (France)
Int'l Joint Research
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[Presentation] Experimental studies on phase equilibria, density and sound velocities of Martian mantle assemblages2021
Author(s)
Siersch N., Xu F., Marceline, A.-E., Greaux S., Rivoldini A., Kuwahara H., Kondo N., Wehr N., Menguy N., Kono Y., Higo Y., Plesa A.-C., Badro J. and Antonangeli D.
Organizer
AGU Fall Meeting. New Orleans (USA, Online)
Int'l Joint Research / Invited
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