Data for "Energetics of brittle-semibrittle transition in quartz sandstone"

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Title
Data for "Energetics of brittle-semibrittle transition in quartz sandstone"
Contributors
Kanaya, Takamasa (creator)
Hirth, Greg (creator)
Doi
10.7301/Z0XG9P2V
Date Created
2016-11-01
Abstract
Triaxial compression experiments were conducted on a quartz sandstone at effective pressures to 175 MPa and temperatures to 900°C. Our samples show a transition from brittle faulting to semibrittle faulting with an increase in both PT. The yield behavior of semibrittle samples is consistent with a compactant elliptical cap at low strain, but it changes to a dilatant Mohr-Coulomb relationship at high strain, indicating expanding yield surfaces. Microstructural observations indicate that semibrittle deformation is accommodated by cataclastic flow involving shear-enhanced compaction and grain crushing. Our semibrittle samples show that elevated temperatures induce significant compaction, and we conclude that these cataclastic mechanisms are enhanced by subcritical microcracking. These results illustrate that temperature is an important factor influencing the brittle-cataclastic flow transition in porous rocks. Analysis of energy partitioning suggests that there is little contribution from dislocation mechanisms to the semibrittle deformation in our experiments. For both brittle and semibrittle faulting regimes, our analysis indicates that frictional slip along distributed, intergranular shear bands dissipates ~95-97% of the pre-failure energy input. This observation suggests that shear bands are the primary deformation process that governs the shape of stress-strain curves through reducing hardening moduli in porous rocks. We conclude that the brittle-ductile transition observed in our experiments results from an increase in shear fracture energy and the enhancement of thermally-activated cataclastic flow with increasing PT. Our results have a range of geophysical implications, including the stability of fault slip, estimates for in-situ stress in sediments, and numerical models of granular deformation.
Keywords
Rheology
Fractures
Faults (Geology)
Earth (Planet)
Crust
Brittle-ductile transition
Rock deformation
Microstructure
Notes
Funded by the National Science Foundation (EAR-1315784), the Southern California Earthquake Center (contributions 12153, 13123, 15117), and a Geological Society of America Graduate Research Grant
Access Conditions
This work is licensed under a Creative Commons Attribution 4.0 International License

Citation

Kanaya, Takamasa, and Hirth, Greg, "Data for 'Energetics of brittle-semibrittle transition in quartz sandstone'" (2016). Brown University Open Data Collection. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0XG9P2V

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