37 Tectonics

Wednesday, 11 March 2026
8:30 AM - 10:00 AM
RCC, 106

The Effects of Hydrolytic Weakening in Quartz-Rich Rocks from the Raft River Detachment Shear Zone

Paper number: 37-3
Program: Technical Sessions
Time: 9:15 AM – 9:30 AM

Authors

Abstract

Quartz is an abundant component of the Earth’s crust, and its mechanical properties control a variety of geological processes. Among the many mechanisms that affect quartz’s strength, hydrolytic weakening remains poorly understood. Hydrolytic weakening – the reduction in the strength of quartz due to the presence of water, either as fluid inclusions or structurally bound hydroxyl groups – has been extensively studied through laboratory experiments. However, experimental results remain inconclusive about the correlation between strain and water content. 

The primary objective of this project is to investigate the effects of hydrolytic weakening in quartzite mylonite's from the Raft River detachment shear zone (Utah). The shear zone, localized in the Elba Quartzite (composed of ~90% quartz, ~10% muscovite), exhibits a finite strain gradient along the transport direction and significant water-rock interaction, providing a natural laboratory to investigate the hydrolytic weakening mechanisms on quartz deformation. We combine petrographic analysis with scanning electron microscopy, cathodoluminescence (CL), electron backscatter diffraction (EBSD), and Fourier transform infrared spectroscopy (FTIR) to investigate the relationship between water distribution, water content, and strain magnitudes in the quartzite mylonite's. Combined CL and FTIR results reveal healed microfractures associated with high water content. EBSD and FTIR data show systematically higher water content in recrystallized grains. These preliminary results suggest that water infiltrated the mylonite through healed fractures and was redistributed in the mylonite by progressive recrystallization, suggesting that the presence of fluids may have initiated recrystallization through hydrolytic weakening. These findings have important implications for our understanding of quartz rheology and strain localization mechanisms in shear zones.  

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411894

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