Deciphering the Role of Deformation in Orogenic Evolution Through Multi-scale Structural Studies in a "Crustal Laboratory", Central Sierra Nevada, California

该项目侧重于多尺度调查，旨在了解与内华达山脉中部发展相关的变形过程。该项目包括地质测绘和变形织物的测量，以及建立一个记录变形织物、应变测量的数据库。野外工作和数字数据库将用于更好地理解在造山带形变局部化的过程。除了研究的科学目标外，该项目还有助于实现与社会和国家相关的目标，包括培养重要的STEM（科学、技术、工程和数学）学科的研究生和本科生；发展一个地理信息系统格式的数字数据库，供科学界和公众使用；开发可用于教学和研究的广泛、综合的该地区地质数字实地指南；并且开发面向公众的虚拟实地考察。本科学生的培训将包括参加大学的UTR项目，这是一个多学科的、以学习者为中心的研究体验，包括实地研究，然后是实验室研究，最终以专业出版物和演讲结束。本方案将努力扩大代表性不足的群体在地球科学领域的参与。该项目涉及与一位来自加拿大的科学家的国际合作，该项目将有助于东道国机构的研究基础设施。研究结果将通过科学文献中的同行评议出版物、专业学会会议上的报告以及通过在学校和国家公园的讲座向公众宣传等方式公布。样本将在大学存档，数字数据将通过大学服务器和社区数据库提供。此外，所有数据将与约塞米蒂国家公园和其他保护区的工作人员共享。造山带在岩石圈观测尺度范围内的流变非均质性导致构造边界条件在中间尺度上的变形分区，使得用单尺度模型将小尺度构造与构造尺度过程和边界条件联系起来是不现实的。提出的研究是一项多尺度研究，旨在利用最先进的自洽多阶幂律方法（MOPLA）将多尺度变形纳入其公式，并为将小尺度研究连接到构造尺度变形条件和过程提供了严格的手段，以连接变形过程、构造和造山演化。通过将MOPLA应用于数据丰富的内华达山脉中部，研究构造与造山带演化的关系以及由此产生的多尺度变形。数十年来，内华达山脉中部收集了大量与填图和地质年代学相关的多尺度构造、应变和岩石学数据。这些定义了一个明显的中生代幕式变形、板块运动和与幕式岩浆作用平行的构造制度的历史。将创建一个基于地理信息系统（GIS）的新数据集和现有数据集的综合，然后与MOPLA集成，以构建和测试多尺度建模预测。这项工作将验证造山带内变形部分受演化变形分配控制的假设，演化变形分配进一步受到与幕式岩浆活动有关的热效应和体积增加的调节。这将通过建模来检验四个必然的、相互关联的假设进行调查：(1)内华达山脉中部在所有尺度上观察到的结构变化通常是由随时间变化的变形分割引起的，而不是板块运动的移动。(2)内华达山脉中部岩体的岩浆组构取向不是整体变形场的明显增量，而是在分区流场中发育的局部组构。(3)幕式变形主要受幕式岩浆作用的驱动。(4)造山带内体积缩短主要是由地壳沿宽的低应变域增厚而不是沿局部的高应变带运动引起的。由于单尺度构造研究和古造山带的板块运动重建有限，多尺度变形正演模拟将有助于更好地理解如何整合局部观测以探索其区域意义。

This project focuses on a multiscale investigation aimed at understanding deformation processes associated with the development of the central Sierra Nevada mountain range. The project involves geologic mapping and measurement of deformation fabrics and the building of a data bases that records deformation fabric, strain measurements. The fieldwork and digital database will be used to better understand processes that contribute to the localization of deformation in mountain belts during orogenic events. In addition to the scientific objectives of the study, the project is contributing to socially and nationally relevant goals, including the training of graduate and undergraduate students in an important STEM (Science, Technology, Engineering and Mathematics) discipline; development of a digital data base in a geographic information system (GIS) format that will be made available to the scientific community and the public; development of an extensive, integrated digital field guide to the geology of the region that can be used for teaching and research; and the development of virtual field trips that will be publically available. Undergraduate student training will involve participation in the university's UTR program, a multidisciplinary, learner-centered research experience that includes field studies followed by lab research, culminating in professional publications and presentations. Efforts will be made in this program to broaden the participation of underrepresented groups in the geosciences. The project involves international collaboration with a scientist from Canada, and the project will contribute to research infrastructure at the host institution. Results of the research will be made available through peer-reviewed publications in the scientific literature, presentations at professional society meetings, and public outreach through lectures at schools and national parks. Samples will be archived at the university, and digital data will be made available via university servers and community databases. In addition, all data will be shared with Yosemite National Park and other conservation area personnel.Rheological heterogeneity in orogens over the range of lithospheric observation scales leads to deformation partitioning of tectonic boundary conditions throughout intervening scales, making it unrealistic to apply single-scale models to connect small-scale structures to tectonic scale processes and boundary conditions. The proposed research is a multi-scale investigation aimed at connecting deformation processes, tectonics, and orogenic evolution using a state of the art, self consistent Multi-Order Power-Law Approach (MOPLA) which incorporates multi-scale deformation in its formulation and provides a rigorous means for bridging small-scale studies to tectonic-scale deformation conditions and processes. The relationship of tectonics to orogenic evolution and the resulting multi-scale deformation will be investigated by applying MOPLA to the data rich central Sierra Nevada where extensive multi-scale structural, strain, and petrological data linked to mapping and geochronology have been collected over several decades. These define an apparent Mesozoic history of episodic deformation, plate motions, and tectonic regimes that parallel episodic magmatism. A geographic information system (GIS)-based synthesis of new and existing datasets will be created and then integrated with MOPLA to construct and test multi-scale modeling predictions. This work will test the hypothesis that intra-orogenic deformation is partly controlled by evolving deformation partitioning that is further modulated by the thermal effects and volume addition related to episodic magmatism. This will be investigated through modeling to test four corollary, interrelated hypotheses: (1) Structural variations observed in the central Sierra Nevada at all scales often arise from time-dependent deformation partitioning rather than shifting plate motions. (2) Magmatic fabric orientations in central Sierra Nevada plutons represent local fabrics developed in partitioned flow fields rather than distinct increments of the bulk deformation field. (3) Episodic deformation is primarily driven by the effects of episodic magmatism. (4) Intra-orogenic bulk shortening is accommodated primarily by crustal thickening along broad, low strain domains rather than motion along localized, high strain zones. As single scale structural studies and plate motion reconstructions for older orogens are limited, forward modeling of multi-scale deformation will lead to a better understanding of how to integrate local observations to explore their regional significance.