Field and microstructural investigation of strain localization processes, texture development, and the rheology of naturally deformed lower crust

地壳和上地幔的流变学（即变形行为）对一系列行星过程施加了基本的控制，从精确模拟板块构造，到估计冰川后反弹的模式和地震变形的传播。海平面上升的模型同样受到我们对地壳和上地幔黏度结构的理解的影响，对沿海社区的人类产生直接影响，因为他们的未来规划和发展是基于模型预测的。因此，我们准确预测全球和局部海平面变化的社会影响的能力，在一定程度上取决于对控制地球物质变形行为的条件和过程的细致理解。这项研究将从一些最难以接近和最不了解的深层地壳物质中得出流变学的经验估计，从而为各种模型输入和全球过程提供信息。研究生和本科生的教学和培训是本研究概述的综合研究工作的基石，特别关注妇女参与国际STEM（科学，技术，工程和数学）研究经验。本研究进一步旨在利用新的数字数据库和科学工具（例如用于结构分析的StraboSpot数据库）的发展，促进原始数据和科学发现的自由传播，并寻求开发用于晶体固体表征的新工具，为其他STEM领域的技术转移和突破提供潜力。岩石圈中许多矿物（如橄榄石、石英）和矿物集合体（如橄榄石和正辉石）的粘性流变学研究已经有一段时间了，但多相集合体（如辉长岩——构成下地壳的主要岩性）的流变学研究仍然很有限。由于斜长石和辉石是下地壳中最常见的矿物之一，研究控制它们变形的微观力学过程对于推进对一系列地球动力学过程的理解至关重要。特别是在活动造山环境中，通过间接观察方法进行构造推断的能力取决于对高温粘性流动中形成的结构结构和晶体结构起源的了解。因此，从野外和微观结构调查中获得的流变学信息仍然至关重要，因为这些暴露记录了自然条件下深部地壳变形过程中形成的岩石微观结构、变形机制和晶体结构。本研究以野外调查为基础，结合显微结构研究、应变分析和电子背散射衍射结构分析，重点研究澳大利亚中部Mount Hay地块深部自然变形、成分不均匀的麻粒岩。利用这些方法，本研究将提供定量约束：(1)地壳深部变形非均质性和应变局部化过程；（ii）成分和构造控制多相砾岩变形的微观力学；(3)非均质下地壳岩性的流变学。此外，本研究旨在探索应变几何在斜长岩（如辉长岩）中晶体优先取向（CPO）发展中的作用，为改善依赖于结构各向异性（如地震各向异性、粘性各向异性、熔体渗透）的岩石圈过程的解释提供了巨大的潜力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The rheology (i.e. the deformational behavior) of Earth's crust and upper mantle exerts a fundamental control on a range of planetary processes, from accurately modeling plate tectonics, to estimating patterns of post-glacial rebound and the propagation of seismic deformation. Models of sea level rise are similarly influenced by our understanding of the viscosity structure of the crust and upper mantle, having direct consequences for humans in coastal communities that base their future planning and development on model predictions. Thus, our ability to accurately predict the societal effects of global and local sea level change is, in part, dependent upon a nuanced understanding of the conditions and processes that control the deformational behavior of Earth materials. This study will produce empirical estimates of rheology from some of the least accessible, and least understood, deep crustal materials, thus informing on various model inputs and global processes. Teaching and training of graduate and undergraduate students are cornerstones of the integrated research efforts outlined in this study, with a particular focus on the participation of women in international STEM (Science, Technology, Engineering and Mathematics) research experiences. This study further aims to leverage the development of new digital databases and scientific tools (e.g., the StraboSpot database for structural analysis) to facilitate the free dissemination of primary data and scientific findings, and it seeks to develop new tools used for the characterization of crystalline solids, offering potential for technology transfer and breakthroughs in other STEM fields. The viscous rheologies of many minerals (e.g., olivine, quartz) and mineral aggregates (e.g., olivine and orthopyroxene) in the lithosphere have been studied for some time, yet rheologies for polyphase aggregates (e.g., gabbro -- the dominant lithology comprising the lower crust) remain poorly constrained. Because plagioclase and pyroxene are among the most common minerals in the lower crust, investigating the micromechanical processes that govern their deformation is fundamental to advancing the understanding of a range of geodynamic processes, particularly in active orogenic settings where the ability to make tectonic inferences from indirect methods of observation rests upon knowledge as to the origin of structural fabrics and crystallographic textures developed during high-temperature viscous flow. Rheological information obtained from field-based and microstructural investigations of exhumed deep crustal lithospheric sections thus remain critical as these exposures record within them the rock microstructures, deformation mechanisms, and crystallographic textures formed in the deep crust during deformation under natural conditions. This research focuses on naturally deformed, compositionally heterogeneous deep crustal granulite exposures in the Mount Hay block of central Australia and is rooted in field-based investigation, and integrated with microstructural studies, strain analysis, and textural analysis using electron backscatter diffraction. Using these methods, this research will provide quantitative constraints on: (i) deformation heterogeneity and strain localization processes in the deep crust; (ii) the compositional and tectonic controls the micromechanics of deformation in polyphase aggregates; and (iii) the rheology of heterogeneous lower crustal lithologies. Further, this study aims to explore the role of strain geometry on the development of crystallographic preferred orientation (CPO) in plagioclase-dominated rocks (e.g., gabbro), offering immense potential for improving the interpretation of lithospheric processes that depend on fabric anisotropy (e.g., seismic anisotropy, viscous anisotropy, melt percolation).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.