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

该项目侧重于一项旨在了解与内华达山脉中部山脉发展有关的变形过程的多尺度调查。该项目涉及对变形组构的地质测绘和测量，以及建立一个记录变形组构、应变测量的数据库。实地考察和数字数据库将用于更好地了解造山活动期间有助于山带形变定位的过程。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有关的目标，包括对一个重要的STEM(科学、技术、工程和数学)学科的研究生和本科生进行培训；开发一个将向科学界和公众提供的地理信息系统(GIS)格式的数字数据库；编制一本广泛的、可用于教学和研究的该地区地质综合数字实地指南；以及开发将向公众提供的虚拟实地考察。本科生培训将包括参与大学的UTR计划，这是一种多学科的、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，最后是专业出版物和演示文稿。该计划将努力扩大未被充分代表的群体在地球科学领域的参与。该项目涉及与一名加拿大科学家的国际合作，该项目将为东道国机构的研究基础设施做出贡献。研究结果将通过科学文献的同行评议出版物、在专业学会会议上的陈述以及通过在学校和国家公园的讲座进行公开宣传来提供。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工作人员共享。在岩石圈观测尺度范围内，造山带的流变性不均匀导致构造边界条件在中间尺度上的变形划分，因此使用单尺度模型将小尺度结构与构造尺度过程和边界条件联系起来是不现实的。这项研究是一项多尺度的研究，旨在使用最先进的自洽多阶幂定律方法(MOPLA)将变形过程、构造和造山演化联系起来，该方法将多尺度变形纳入其公式中，并为小规模研究与构造尺度变形条件和过程之间的联系提供了一种严格的手段。通过在数据丰富的内华达山脉中部应用MOPLA，将研究构造与造山演化和由此产生的多尺度变形的关系，在那里，几十年来收集了与测绘和地质年代学有关的广泛的多尺度构造、应变和岩石学数据。这些定义了一段明显的中生代幕式变形、板块运动和与幕式岩浆活动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合成，然后与MOPLA集成，以构建和测试多尺度建模预测。这项工作将检验造山内变形部分受控于演化的变形分配的假说，而演化的变形分配又受与幕式岩浆活动有关的热效应和体积增加的进一步调制。将通过模拟来研究这一点，以检验四个相互关联的推论：(1)在所有尺度上观察到的内华达山脉中部的结构变化往往源于依赖于时间的形变分割，而不是移动的板块运动。(2)内华达山脉中部深成岩浆组构的取向代表了局部组构在分割的流场中发育，而不是整体变形场的明显增量。幕式变形主要受幕式岩浆作用的驱动。(4)造山内块体缩短主要是由地壳沿宽广的低应变域增厚，而不是沿局部的高应变区运动。由于对老造山带的单尺度结构研究和板块运动重建是有限的，多尺度变形的正演模拟将导致更好地理解如何整合当地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.