EAR-PF: Advanced statistical analysis to relate microstructural fabrics and finite strain in ductilely deformed rocks

EAR-PF：高级统计分析，将延性变形岩石中的微观结构结构和有限应变联系起来

• 批准号: 2053072
• 负责人: Alexander Lusk
• 金额: $ 17.4万
• 依托单位: Lusk, Alexander Dmitri
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2022-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2053072&HistoricalAwards=false
• 关键词: EAR; PF; Advanced; statistical; analysis

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Dr. Alexander Lusk has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at the University of Wisconsin Madison. Geologists characterize how rocks deform by measuring a quantity called finite strain. Finite strain is conceptualized in three dimensions as an ellipsoid. When rocks are not deformed, the 3-D object is a sphere; with increasing deformation, it becomes more elliptical. However, most deformed rocks do not have any large-scale indicators that record finite strain. As a result, geologists make microscope slides of rocks to study microscopic features called microstructures. The goals of Dr. Lusk’s project are two-fold: (1) to provide methods of characterizing finite strain uncertainty (i.e. error bars) in three dimensions to better understand rock deformation, and (2) to provide geologists with methods to relate rock microstructures developed in quartz (a common crustal rock constituent) to the finite strain experienced during deformation. To characterize finite strain, Dr. Lusk will apply statistical methods to rocks that contain quartz pebbles, which preserve a direct record of finite strain. During his postdoctoral fellowship, Dr. Lusk will carry out an education plan involving the following: (1) development of an undergraduate level, exploration based virtual education module that will aim to make students comfortable with measuring and interpreting finite strain in the field; (2) development of software for the statistical analysis of finite strain, integrated in the StraboSpot field app; (3) mentoring of two UW-Madison students in undergraduate research projects. This project aims to evaluate the response of rock microstructure developed in ductile quartz-rich rocks to the finite strain magnitude, geometry, and strain path in which deformation occurred. The proposed approach differs from previous work in that it applies multivariate statistical methods to quantitatively characterize ellipsoidal finite strain data – with a measure of uncertainty – for the first time. The key to statistical analysis of ellipsoids is that orientations and magnitudes, while independent measurements, must be combined and transformed into an ellipsoid tensor; in tensor form, multivariate statistical analysis can be applied. The project will be carried out by analyzing finite strain and rock microstructure in the ductile Bygdin (Norway) and Funzie (Scotland) quartz-rich metaconglomerates. Finite strain will be determined at the outcrop scale by measuring clast orientation and all three ellipsoid axes to constrain clast shape. At the grain scale, two measures of finite strain will be determined: (1) the grain shape and shape preferred orientation of relict metamorphic grains, and (2) the spatial relationship of relict metamorphic grain center points. Electron backscatter diffraction will be used for microstructural characterization, including measurement of grain shape, crystallographic vorticity axis orientation, and crystallographic preferred orientation. By relating statistical measures of finite strain directly to rock microstructural fabrics, Dr. Lusk aims to improve our current understanding of how finite strain and strain history is preserved in the microstructural record and to provide structural geologists with methods to infer strain history without a direct measurement of finite strain.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项全部或部分由《2021 年美国救援计划法案》（公法 117-2）资助。Alexander Lusk 博士已获得 NSF EAR 博士后奖学金，在威斯康星大学麦迪逊分校开展研究和教育计划地质学家通过测量称为有限应变的量来描述岩石的变形情况。有限应变在三维空间中被概念化为椭球体。当岩石不变形时，三维物体是一个不断增大的球体。然而，大多数变形的岩石没有任何记录有限应变的大型指标，因此，地质学家制作岩石的显微镜幻灯片来研究称为微观结构的微观特征。有两个方面：(1) 提供在三个维度上表征有限应变不确定性（即误差条）的方法，以更好地了解岩石变形；(2) 为地质学家提供将岩石联系起来的方法为了表征有限应变，Lusk 博士将对石英（一种常见的地壳岩石成分）中形成的微观结构应用统计方法，以在博士后期间保存有限应变的直接记录。获得奖学金后，Lusk 博士将实施以下教育计划：(1) 开发本科阶段的虚拟教育模块，涉及基于探索的虚拟教育模块，旨在使学生能够轻松测量和解释现场有限应变； (2) 开发有限应变统计分析软件，集成到 StraboSpot 现场应用程序中；(3) 指导两名威斯康辛大学麦迪逊分校学生的本科研究项目，旨在评估延性石英开发的岩石微观结构的响应。所提出的方法与以前的工作不同，它应用多元统计方法来定量表征椭圆体有限应变数据 - 通过测量。不确定性 - 椭球统计分析的关键是方向和大小，虽然是独立的测量，但必须组合并转换为椭球张量；以张量形式，可以应用多元统计分析。通过分析富含延性石英的 Bygdin（挪威）和 Funzie（苏格兰）超砾岩中的有限应变和岩石微观结构来确定露头尺度的有限应变。测量碎屑取向和所有三个椭球轴以约束碎屑形状，在晶粒尺度上，将确定有限应变的两个测量值：（1）残余变质晶粒的晶粒形状和形状择优取向，以及（2）晶粒形状的空间关系。电子背散射衍射将用于微观结构表征，包括通过相关统计测量测量晶粒形状、晶体涡度轴方向和晶体方向。 Lusk 博士将有限应变直接应用于岩石微观结构结构，旨在提高我们目前对如何在微观结构记录中保存有限应变和应变历史的理解，并为结构地质学家提供无需直接测量有限应变即可推断应变历史的方法。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。