2023 Fiscal Year Final Research Report
Direct observation of mantle-water reaction in subduction zone using neutron imaging
| Project/Area Number |
21K18641
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| Research Category |
Grant-in-Aid for Challenging Research (Exploratory)
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| Allocation Type | Multi-year Fund |
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| Review Section |
Medium-sized Section 17:Earth and planetary science and related fields
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Project Period (FY) |
2021-07-09 – 2024-03-31
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| Keywords | 中性子イメージング / 水 / 高圧 / 高温 |
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| Outline of Final Research Achievements |
Using neutron diffraction experiments, I succeeded in directly determining the structure of hydrous sodium silicate melts (including hydrogen positions), which was not possible by X-ray diffraction. I obtained structural data of silicate melts under pressure conditions up to 5 GPa, and I’m able to understand the pressure dependence of each bond. I found that the hydrogen-oxygen bond distance is sensitive to pressure and I concluded that pressure-induced polymerization occurs.
I constructed an experimental cell that can maintain stable high temperature and high pressure conditions for a long time, and succeeded in obtaining the neutron imaging under high temperature and high pressure conditions. I confirmed that there is a correlation between the amount of hydrogen and the intensity in the imaging (degree of absorption), which enables us to directly observe the distribution of hydrogen in the sample.
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| Free Research Field |
高圧地球科学
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| Academic Significance and Societal Importance of the Research Achievements |
地球科学という観点に立つと、軽い元素を対象にした研究を避けることはできない。特に地球という惑星を考えた場合、「水」は極めて重要な物質である。そこで、水を研究する上で有効な中性子ビームを活用することに目を付けた。本研究で実現した地球内部を再現した高温高圧条件下における中性子イメージングは、世界的に見ても非常に珍しく、先導的な研究・技術である。高温高圧発生プレスと中性子イメージング技術を組み合わせた測定システムの構築・最適化は大きなブレイクスルーであり、他の研究テーマにも適用されることが期待される。つまり、高温高圧中性子イメージングを利用した今後の地球科学の発展にも繋がり、極めて波及効果が高い。
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