Collaborative Proposal: Fluid flow metamorphism and strain localization in mid-crustal shear zones

本项目研究地壳中部（深度大于12公里）断裂带的组成和强度与流体、变质作用和变形局部化之间的关系。该项目将重点放在与犹他州Raft River变质核杂岩相关的韧性断裂带上，以便在断裂过程中限制流体的来源和数量。这项研究结合了野外地质制图、矿物结构分析、化学分析以及确定断层运动时间的分析。该项目有可能将分析数据与特定的流体来源联系起来，并更好地在地壳尺度上约束流体流动。该项目由一名早期职业教师领导，包括硕士研究生和本科生。路易斯安那大学拉斐特分校（University of Louisiana at Lafayette）的第一代和少数族裔大学生也参与其中。该项目包括一项支持北卡罗莱纳州西部农村地区K-12教育的推广工作，其中包括由本科生开发的地质时间资源。该项目的目的是提高对与变质岩心杂岩相关的滑脱剪切带中流体-岩石相互作用的认识。含水变质矿物记录了地壳深处大气流体的存在。尽管大气流体的清晰记录一直延伸到地壳的中下深度，但许多化学和岩石学上的不一致仍然存在。在造山崩塌过程中，上地壳通过脆弱的正断层变薄，而韧性较强的下地壳横向流动。伸展的局部化最终导致滑脱剪切带和变质核杂岩的形成。下地壳韧性伸展的特征是高热通量、花岗岩体侵入和混染岩片麻岩穹丘，与变质/岩浆流体有关。在挖掘过程中，两个流体储层（岩浆/变质水和地表大气水）之间存在竞争。本项目利用氢、氧稳定同位素数据作为流体源和流体-岩石交换的示踪剂，对大陆伸展过程中流体-岩石相互作用提供约束条件。同位素数据与特定的流体来源相关联，以更好地约束地壳尺度流体流动的水文，从而弥合实验得出的岩石强度与现场观测之间的差距。该项目由地球科学部的构造学项目和促进竞争性研究的既定项目（EPSCoR）共同资助。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。

This project investigates the relationship between fluids, metamorphism, and localization of deformation on the composition and strength of fault zones in middle regions of the crust (depths greater than 12 kilometers). The project focuses on the ductile fault zone associated with the Raft River metamorphic core complex in Utah, in order to constrain both the source and the amount of fluid during faulting. The study incorporates geologic mapping in the field, analyses of mineral structures, chemical analyses, and analyses to determine the timing of movement along the fault. The project has the potential to tie analytic data to specific fluid sources and better constrain fluid flow at a crustal-scale. This project is led by an early career faculty member and includes Masters-level graduate and undergraduate students. First-generation and minority college students at the University of Louisiana at Lafayette are also involved. The project incorporates an outreach effort to support K-12 education in rural western North Carolina that includes geologic time resources developed by undergraduate students.The goal of this project is to improve the understanding of fluid-rock interaction in detachment shear zones associated with metamorphic core complexes. Hydrous metamorphic minerals record the presence of meteoric fluids at great depths within the crust. Despite the clear record of meteoric fluids down to mid- to lower-crustal depths, many chemical and petrologic inconsistencies remain. During orogenic collapse, the upper crust thins by brittle normal faulting while the ductile lower crust flows laterally. Localization of extension eventually leads to the formation of a detachment shear zone and metamorphic core complex. Ductile extension in the lower crust is characterized by high heat fluxes, granitic intrusion, and migmatitic gneiss domes, associated with metamorphic/magmatic fluids. During exhumation, there is competition between two fluid reservoirs (magmatic/metamorphic and meteoric water from surface sources). This project uses hydrogen and oxygen stable isotope data as tracers of fluid source and fluid-rock exchange to provide constraints on fluid-rock interaction during continental extension. Isotopic data is linked to specific fluid sources to better constrain the hydrology of crustal-scale fluid flow, in order to bridge the gap between experimentally-derived rock strengths, and field observations.This project is jointly funded by the Tectonics program in the Division of Earth Sciences and the Established Program to Stimulate Competitive Research (EPSCoR).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.