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

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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.