| 研究課題/領域番号 |
20KK0079
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| 研究機関 | 東京大学 |
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研究代表者 |
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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| 研究分担者 |
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), 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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| 研究期間 (年度) |
2020-10-27 – 2024-03-31
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| キーワード | EBSD / Hough Transformation / Dictionary Indexing / Antigorite / Lizardite |
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| 研究実績の概要 |
We carried out analysis of serpentinite schist. We performed EBSD mapping of antigorite schist to complement the work done in the previous year. We carried out very careful sample preparation including consideration of the orientation of the sample with respect to the foliation. We also experimented with a range of different conditions for polishing the surface. The results produced greater than 70% indexing rate using the traditional indexing system that is based on Hough Transformations of the Kikuchi diffraction patterns. This large data set was then used to examine what sort of improvements could be obtained using the Dictionary Indexing approach. We were unable to visit our foreign collaborator in person but were able to discuss the results on line and went the data for him to continue analysis in USA. Dictionary indexing resulted in a similar microstructural map but with much greater resolution. The Dictionary Indexing approach does not allow for non indexed pixels so the indexing rate is 1000%. We carried out similar mapping of lizardite in a serpentinite sample. This is a low T form of serpentinite and is mechanically much softer than antigorite and subject to beam damage when analysed in SEM. For these reasons data on crystal orientation is very limited. We now have a good data set for this low T serpentinite material. Our initial results show the importance of twinning in antigorite and are able to resolve some of the issues with rotational psedo symmetry present in previous EBSD analyses of antigorite.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
Due to the pandemic there have been severe restrictions on the freedom to travel abroad. As a result of this we have not been able to carry out the laboratory visits that we planned with Prof. Marc DeGraef. This has hindered our efforts to develop a system that is best suited to our own needs. We wish to study minerals with complex crystal structures and low crustal symmetry whereas Prof DeGraef is mostly concerned with metal crystals that have a high degree of symmetry. Many of the minerals we are interested in that make up fault rock also have low degrees of crystallinity which further complicates the analysis. We have been able to communicate with each other using the opportunities offered by online links. With the opening of the borders in many countries we now plan to meet face to face.
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| 今後の研究の推進方策 |
Our plans for the next stage of this work are to meet with Professor DeGraef to discuss how best to adapt the Dictionary Indexing system to meet the needs of analysing sheet silicate minerals that are prevalent in fault rocks. At the same time we will experiment with the best sample preparation procedures and the best analytical conditions to analyse mechanically weak minerals such as lizardite, chrysotile and clay minerals.
There are very few examples of EBSD data obtained from such minerals and to verify that the Kikuchi patterns are accurately able to identify these minerals it is desirable to have an alternative method of mineral identification. We have identified laser Raman as the most effective technique and plan to carryout micro scale mapping of the samples to identify the type and distribution of the different mineral species in the fault rock samples. We will then compare this to the EBSD results using Hough Transformation and Dictionary Indexing approaches.
We will use the obtained
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| 次年度使用額が生じた理由 |
International travel and onsite collaboration is an important part of this project. Unfortunately due to the severe restrictions on international travel and the uncertainties about whether it would be possible made such planning impractical and we were unable to meet with Prof DeGraef in USA and it was not possible for him to travel to Japan to meet us. We plan to make up for this situation by arranging visits this year. The travel restrictions have also meant that it has not been possible for us to give presentations at international conferences with the possibility of face-to-face interactions with leaders in the field. The financial support originally intended to be used for this purpose in financial year 2021 will now be used in the new year.
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