New developments in EBSD analysis applied to characterization of fault rock microstructure
Project/Area Number |
20KK0079
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Research Category |
Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
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Allocation Type | Multi-year Fund |
Review Section |
Medium-sized Section 17:Earth and planetary science and related fields
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Research Institution | The University of Tokyo |
Principal Investigator |
WALLIS R・Simon 東京大学, 大学院理学系研究科(理学部), 教授 (30263065)
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Co-Investigator(Kenkyū-buntansha) |
瀬戸 雄介 神戸大学, 理学研究科, 講師 (10399818)
永冶 方敬 東京大学, 大学院理学系研究科(理学部), 助教 (10795222)
吉田 健太 国立研究開発法人海洋研究開発機構, 海域地震火山部門(火山・地球内部研究センター), 副主任研究員 (80759910)
大柳 良介 国立研究開発法人海洋研究開発機構, 海域地震火山部門(火山・地球内部研究センター), 特別研究員(PD) (90835729)
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Project Period (FY) |
2020-10-27 – 2024-03-31
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Project Status |
Granted (Fiscal Year 2022)
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Budget Amount *help |
¥18,720,000 (Direct Cost: ¥14,400,000、Indirect Cost: ¥4,320,000)
Fiscal Year 2023: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2022: ¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000)
Fiscal Year 2021: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
Fiscal Year 2020: ¥8,580,000 (Direct Cost: ¥6,600,000、Indirect Cost: ¥1,980,000)
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Keywords | EBSD / Serpentinite / Hough Indexing / Dictionary Indexing / Microstructure / Hough Transformation / Antigorite / Lizardite / 断層岩の微細組織 / 蛇紋石 / 断層岩 / 微細組織 / 情報科学 |
Outline of Research at the Start |
地震発生は断層におけるずれが原因なので、地震研究には断層の中央部に分布する「断層岩」の特徴究明が重要である。しかし、これらの変形岩の微細組織を可視化する有効な手立てが見つかっていない。そのために、スロー地震の発生メカニズムをミクロスケールの変形様式から理解することが困難な現状がある。本研究は、この空白を埋めるために、材料科学分野の権威である米国のCarnegie Mellon UniversityのDe Graef博士によって開発された最先端の後方散乱電子回折法(EBSD)とビッグデータ情報科学を融合した新手法を同氏の研究室で習得し、岩石学分野に導入する予定である。
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Outline of Annual Research Achievements |
During the last academic year Wallis accompanied a student to carry out field work in the Franciscan terrane of the western USA. We collected numerous samples for transport back to Japan and more detailed microstructural analysis. These samples were metamorphosed sandstone and mudstone and a variety of fault rocks including deformed serpentinite. Several samples of serpentinite were selected for EBSD analyses at University of Tokyo. Polished thin sections of the serpentinite samples were carefully prepared including 1/4 micron diamond polishing. The surface was then treated with colloidal silica following the polishing procedures established by the group at the University of Tokyo to optimize removal of surface damage. EBSD mapping of this sample were then prepared for an area of 0.5 mm^2 and the resulting data including all the Kikuchi patterns were saved to a hard disk. The resulting data set was in excess of 1TB. This data set was used as a test case to apply Dictionary Indexing to the difficult problem of defining the microstructure of serpentinite samples. The data were sent to De Graef at Carnegie Mello University along with the original sample for further complementary analysis using the Oxford Symmetry detector. No significant improvements in data quality were recognized using the more sensitive detectors. The results of DI indexing were used to plot a series of orientation maps that can in turn be used to reveal the microstructure of serpentinite samples with unprecedented completeness.
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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
The international collaboration that is an important part of this project could be fruitfully pursued after the long interruption by the pandemic. We were able to collect a series of important samples for future work and produced concrete results from one sample. These results have shown the viability of the procedure that has been suggested and opened the way for more samples to be studies in a similar way. The results for the analysis of the antigorite rich serpentine sample have been analyzed and the results are far enough advanced to be able to write up the results in the form of a publication in the near future.
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Strategy for Future Research Activity |
In the coming academic year we intend to write up the results that have already been obtained for the antigorite sample and expand the methodology to analyze samples consisting dominantly of talc and chrysotile. In the case of talc there are only a handful of published EBSD mapping studies. These include one by members of the research team for this project. However, there have been no published studies that clearly reveal the microstructure of the talc rich deformed rocks. This is important because talc is proposed as an important low strength domain that forms at the base of the mantle wedge. Low-T serpentinite samples are also highlighted as potentially important but even less is known about the CPO patterns and microstructure of these samples.
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Report
(3 results)
Research Products
(6 results)