A model for the interaction of pressure solution and cataclasis in a brittle shear zone: Saltville thrust at Sharp Gap Knoxville, Tennessee
- Univ. of Louisville, KY (United States). Geology Dept.
- Cleveland State Univ., Cleveland, OH (United States). Dept. of Geology
Dolomitic shales of Rome Formation are thrust over dolomites of the Knox Group under sub-greenschist conditions, forming a 7--8 meter wide brittle shear zone. Within this zone, mesoscopically foliated cataclasites and ultracataclasites are developed subparallel to the zone. The foliation varies from anastomosing to smooth and tightly-spaced as the intensity of deformation increases. Solution surfaces often bound well-developed cataclasite layers of varying grain size and define the foliation. Samples from a 40m section across the thrust zone are analyzed for their mineralogy (with XRD) and quartz/clay content. At smaller scales, EDAX elemental maps are used to study the relationship between mineral concentrations and cataclastic textures. Bulk quartz/clay weight % of the intact rocks of upper and lower plates and that of the shear zone are 65, 38 and 45 respectively, indicating significant pressure solution activity as well as deformation by cataclastic flow brecciation and some twinning. Simultaneous brittle extension and shear of calcite-rich cataclasite layers suggest that they may have been hardened, at least in part, by infusion of calcite (mostly untwinned) from the surrounding volume. Dilation and movement of fluids at the onset of a cataclastic episode would enhance pressure solution. Preferential deposition of calcite at sites of cataclasis gradually results in a porosity reduction, nonuniform pore pressure build up and may suppress pressure solution activity. Renewed cataclasis occurs at higher strain rates and serves to rearrange the zone at various scales. The two mechanisms predominate alternately at different strain rates to accommodate the imposed strain, requiring the sites of cataclastic deformation to shift throughout the shear zone.
- OSTI ID:
- 5936082
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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