Mapping fluid composition in the upper mantle based on fluid geometry
| Project/Area Number |
16K13903
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Multi-year Fund |
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| Research Field |
Petrology/Mineralogy/Economic geology
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2017: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Keywords | 二面角 / 流体 / カンラン石 / 捕獲岩 / 塩濃度 / 二酸化炭素 / 連結度 / カンラン岩 / タルク / アンチゴライト / 地球深部流体 / 揮発性成分 / MT法 / マントル / 超臨界流体 / 粒界 / ソリダス |
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| Outline of Final Research Achievements |
We precisely obtained dihedral angles between olivine and NaCl- (up to 27.5 wt%) and CO2 (XCO2= 0.33 and 0.5)- bearing aqueous fluids at 1-4 GPa and 800-1100°C to reveal the fluid connectivity in the upper mantle. NaCl is now recognized as an important solute in fluids in subduction zone. We found that NaCl significantly decreases the dihedral angle down to < 60° at the pressure and temperature conditions corresponding to the shallow mantle wedge. We found that only 3-5 wt% of NaCl has similarly large effects on the dihedral angle with olivine to that of 15-27.5 wt %. The CO2 increases the dihedral angle at 1 GPa, but at pressures >2 GPa, where magnesite and pyroxene are stable, dihedral angles were smaller than those for pure H2O fluid. Although these results show that it is difficult to obtain the fluid composition from the pore geometry of xenoliths, it is revealed that aqueous fluids are highly connectable in a wide range of the uppermost mantle conditions.
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| Academic Significance and Societal Importance of the Research Achievements |
沈み込み帯などでは、マントルのような地下深部にも地下水（熱水）が存在しており、マグマの生成やマントルの流動などに大きな役割を果たしています。しかしどれくらの量で、どのように分布しているのか、よくわかっていません。それを理解するには、熱水が、岩石を構成する鉱物に弾かれて水滴のように分布するのか、それとも、鉱物をよく濡らして沁み込みやすいのかを知ることが重要です。この研究では、従来よりも幅広いマントルの条件を再現し、熱水が岩石中によく染みることを明らかにしました。この結果は、絶縁体であるはずの岩石からなるマントルが、電気を良く通すという最近の観測結果をうまく説明できます。
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Report
(4 results)
Research Products
(22 results)
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[Journal Article] Nanomorphology of Itokawa regolith particles: Application to space-weathering processes affecting the Itokawa asteroid2016
Author(s)
Matsumoto, T., Tsuchiyama, A., Uesugi, K., Nakano, T., Uesugi, M., Matsuno, J., Nagano, T., Shimada, A., Takeuchi, A., Suzuki, Y., Nakamura, T., Nakamura, M., Gucsik, A., Nagaki, K., Sakaiya, T., Kondo T.
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Journal Title
Geochim. Cosmochim. Acta
Volume: 187
Pages: 195-217
DOI
Related Report
Peer Reviewed / Int'l Joint Research
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