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)对一系列行星过程起着根本的控制作用，从精确地模拟板块构造到估计冰后反弹和地震形变的传播。海平面上升的模型同样受到我们对地壳和上地幔粘性结构的理解的影响，对沿海社区的人类产生直接影响，这些社区将未来的规划和发展建立在模型预测的基础上。因此，我们准确预测全球和当地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材料变形行为的条件和过程的细微差别的理解。这项研究将从一些最难获得和最不了解的地壳深部材料中得出流变性的经验估计，从而为各种模型投入和全球进程提供信息。研究生和本科生的教学和培训是本研究概述的综合研究努力的基石，特别注重妇女参与国际STEM(科学、技术、工程和数学)研究经验。这项研究还旨在利用开发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)来促进主要数据和科学发现的免费传播，并寻求开发用于表征晶体固体的新工具，为其他STEM领域的技术转让和突破提供潜力。岩石圈中许多矿物(例如橄榄石、石英)和矿物集合体(例如橄榄石和斜辉石)的粘性流变学已经研究了一段时间，但多相集合体(例如辉长岩--构成下地壳的主要岩性)的流变性仍然很差。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机械过程对于促进对一系列地球动力学过程的理解是至关重要的，特别是在活动的造山环境中，从间接观察方法做出构造推断的能力取决于对高温粘性流动过程中形成的结构组构和晶体结构的起源的了解。因此，从出土的地壳深部岩石圈剖面的现场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在自然条件下变形时地壳深部形成的岩石微结构、变形机制和晶体结构。这项研究以野外调查为基础，结合显微构造研究、应变分析和电子背散射衍射织构分析，重点研究了澳大利亚中部海山地块地壳深部麻粒岩的自然变形、成分不均匀暴露。利用这些方法，这项研究将对：(I)地壳深部的变形非均质性和应变局部化过程；(Ii)成分和构造控制多相集合体中变形的微观力学；以及(Iii)非均质下地壳岩性的流变性提供定量的约束。此外，这项研究旨在探索应变几何在斜长石为主的岩石(例如辉长岩)中晶体择优取向(CPO)发展的作用，为改进依赖于组构各向异性(例如地震各向异性、粘性各向异性、熔体渗流)的岩石圈过程的解释提供巨大的潜力。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.