284-8 Effects of Water-Related Processes on Quartz Deformation

Session: The Deformation-Metamorphism-Fluid Triplet Governing Plate Boundaries and Orogens

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Quartz is a major component of Earth’s crust, and its mechanical properties significantly influence a variety of geologic principles. Although numerous mechanisms affect quartz’s strength and ductility, hydrolytic weakening prominently remains as a key process. Hydrolytic weakening refers to the reduction of the strength of quartz due to the presence of water, and despite being extensively studied in experimental settings, it remains controversial in natural deformation settings. What few experiments have been conducted on naturally deformed rocks have yielded inconsistent results that show negative, positive, or no correlation between the amount of water present and the amount of deformation experienced. There is currently no direct correlation between water content and the magnitude of strain in naturally deformed rocks.

The goal of this project is to characterize water content and distributions as a function of strain in quartzite samples from the well-studied detachment shear zone associated with the Raft River metamorphic core complex (Utah). The Raft River detachment shear zone is localized in a section of pure quartzite (~90% quartz, ~10% muscovite) that exhibits a finite strain gradient along the transport direction. Using petrographic microscopy, scanning electron microscopy, cathodoluminescence, electron backscatter diffraction, and Fourier transform infrared spectroscopy, we are investigating the relationship between water distribution, water content, and strain magnitude. Preliminary results indicate that water contained primarily around and within relic quartz grains has a positive correlation to the amount of strain experienced by the sample. Results from this study will shed light on the mechanical weakening effect of hydrolytic weakening for crystal plastic deformation of quartz deformed naturally.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8519

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