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The Role of Water in Grain-Scale Deformation Within the Cove Fault Zone, South Central Pennsylvania

O'Kane, Allyson
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1112897244

Abstract Details

2005, Master of Arts (MA), Bowling Green State University, Geology.
Fluids, and water in particular, play an integral role in deformation within the Earth’s crust over a wide range of physical conditions. At low temperatures (<150°C), the effect of water is dominantly mechanical, largely through the effects of pore fluid pressure. At higher temperatures (>300°C), water-related chemical processes, such as diffusive mass transfer, advective mass transfer, and hydrolytic weakening dominate. In the transition between high and low temperature regimes, both mechanical and chemical processes operate and interact in complex ways. The Cove fault zone in south central Pennsylvania contains several map-scale blocks of quartz arenite, which display a wide range of brittle and ductile microstructures. Abundant evidence of fluids is present from map- to lattice-scales, including quartz precipitated in microveins, fluid inclusion planes, and zones of cataclasis, and the removal of quartz along dissolution surfaces. Three different aqueous fluids were identified based on the cathodoluminescence color of quartz precipitated by that fluid, and the homogenization (T h ), last ice melting temperatures (T m ), and salt species from aqueous, two-phase fluid inclusions. Fourier Transform Infrared (FTIR) spectroscopy data indicate that a large amount of water has become incorporated in the lattice of deformed detrital grains, especially those in the proximity of fluid conduits (e.g., microveins). The fluids, based on the oxygen isotopic composition of the quartz precipitated, appear to be derived from basinal brines or metamorphic fluids that were probably driven northwestward along regional aquifers and fault zones. The microstructures in the Cove fault zone indicate that water was important in controlling the operative deformation mechanisms. Although brittle deformation is prevalent, a significant amount of ductile deformation is present. The formation of ductile microstructures at temperatures of less than 250° C is attributed to the presence of water that lowered the temperature threshold for ductile deformation. These fluids not only promoted diffusive mass transfer, but penetrated grain interiors, thereby promoting hydrolytic weakening and crystal-plastic deformation. Furthermore, the chemistry of these fluids may account for the extreme amount of quartz dissolution found in portions of this fault zone.
Charles Onasch (Advisor)
75 p.
Geology
fluid; fluid pathways; quartz; quartz arenites; deformation; ductile; brittle; low temperature

Recommended Citations

Citations

  • O'Kane, A. (2005). The Role of Water in Grain-Scale Deformation Within the Cove Fault Zone, South Central Pennsylvania [Master's thesis, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1112897244

    APA Style (7th edition)

  • O'Kane, Allyson. The Role of Water in Grain-Scale Deformation Within the Cove Fault Zone, South Central Pennsylvania. 2005. Bowling Green State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1112897244.

    MLA Style (8th edition)

  • O'Kane, Allyson. "The Role of Water in Grain-Scale Deformation Within the Cove Fault Zone, South Central Pennsylvania." Master's thesis, Bowling Green State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1112897244

    Chicago Manual of Style (17th edition)

bgsu1112897244
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© 2005, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.