【公開日：2023.07.31】【最終更新日：2023.05.23】
課題データ / Project Data
課題番号 / Project Issue Number
22UT0125
利用課題名 / Title
Microstructural analysis of pure shear deformation experiment
利用した実施機関 / Support Institute
東京大学
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）その他/Others（副 / Sub）-
キーワード / Keywords
olivine, crystallographic preferred orientation (CPO),電子顕微鏡/Electron microscopy
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
キム ナヒョン
所属名 / Affiliation
東京大学
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
UT-103：高分解能走査型電子顕微鏡
UT-007：高分解能分析電子顕微鏡
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Olivine is the most abundant mineral in the upper mantle and its CPO (crystallographic-preferred orientation) explains the seismic anisotropy observed in the upper mantle. To understand the development of the CPO of olivine and its rheology, many rock experiments using the olivine aggregates have been conducted. Pure shear test is one of the effective ways to conclusively determines the shear plane and shear direction of the olivine aggregates and fabric patterns, accordingly. Through pure shear tests, we found that depending on temperature, duration, and strain of the test conditions, anisotropic olivine grains varied in their 3D morphologies from oblate (plate-like) to prolate (pencil-like). Samples with anisotropic olivine grains displayed a crystallographic preferred orientation (CPO), while samples with weakly anisotropic grains had uniform CPOs. The CPO patterns ranged from AG-type (i.e., a uniaxial [010] concentration in the direction of sample shortening) to A-type (i.e., [010] and [100] concentrations in the directions of sample shortening and stretching, respectively) fabrics; intermediate types being most common. The fabric transition from AG-type to A-type was accompanied by a change in grain morphology from oblate to prolate morphology.
実験 / Experimental
In this study, to investigate olivine grain morphologies in three dimensions and explore the development of olivine fabric patterns in detail, we conducted pure shear tests on fine-grained forsterite+diopside (20%) aggregate at diffusion creep condition. We used the carbon die and punches to conduct the pure shear deformation in this study. After the experiments, we analyzed the microstructures and texture of the deformed sample using FE-SEM and EBSD analysis（JEM-2010F JEOL and JSM-7000F+View digital EBSD camera).
結果と考察 / Results and Discussion
After pure shear tests, the sample microstructures were observed from each of the three principal stress directions. Samples with tabular grains displayed a crystallographic preferred orientation (CPO) in olivine, while samples with weakly anisotropic grains had uniform CPOs. The CPO patterns vary from AG-type (i.e., a uniaxial [010] concentration in the direction of sample shortening) to A-type (i.e. [010] and [100] concentrations in the directions of sample shortening and stretching, respectively), with intermediate types being the most common. The fabric transition from AG-type to A-type was accompanied by a change in grain morphology from oblate to prolate morphology. We explain the direct correlation between the olivine morphology and fabrics based on the preferential grain-boundary sliding on the boundary with fewer steps (ledges) in atomic scale. Oblate morphologies with well‐developed grain boundaries parallel to (010) provide easy GBS on the (010) plane along [h0l] directions, while relatively prolate morphologies with boundaries parallel to (010) and elongated to [100] provide easy GBS on (010) plane along [100] directions. Grain boundaries form parallel to a particular crystallographic plane through anisotropic grain growth and such anisotropic grain growth causes fabric transitions during diffusion creep.
図・表・数式 / Figures, Tables and Equations
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
I thank S. Koizumi, K. Yabe, M. Fukukawa, and A. Takeuchi for their technical assistance and discussion.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
-
N. Kim, Olivine Morphology and Fabric During Diffusion Creep: Pure Shear Experiments, Journal of Geophysical Research: Solid Earth, 127, (2022).
DOI: 10.1029/2021JB023613
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件