Natural and hot isostatically pressed dolomite aggregates were experimentally deformed at effective pressures of Pe = 50 ?? 400 MPa, temperatures of 400 ?? 850??C, and strain rates of ε& = 1.2x10-4 s-1 to 1.2x10-7 s-1. Coarse- and fine-grained dolomite deformed at low temperature (T ≤ 700??C for coarse-grained natural dolomite, T < 700??C for fine-grained natural and synthetic dolomite) exhibit mechanical behavior that is nearly plastic; differential stresses are insensitive to strain rate, fitted either by a power law no⎟⎟⎠⎞⎜⎜⎝⎛−=??σσεε31&& with n values that range from 12 to 49 or an exponential law ([31exp )] σσαεε−=o&& with exponential law term α values from 0.023 to 0.079 MPa-1. Microstructures of samples deformed at low temperatures include mechanical twins, and undulatory extinction suggesting that twin glide and dislocation slip are the predominant deformation mechanisms. At high temperatures (T ≥ 800??C) flow strengths of coarse- and fine-grained dolomite depend more strongly on strain-rate and exhibit pronounced temperature dependencies. Microstructures of coarse-grained dolomite samples deformed at T ≥ 800??C include undulatory extinction and fine recrystallized grains suggesting that recovery and dynamic recrystallization contribute to dislocation creep at these conditions. By comparison with lower temperature deformation, mechanical twinning is unimportant. Fine-grained synthetic dolomite deformed at high temperature (T ≥ 700??C) exhibits nearly linear (Newtonian) viscous behavior, with n = 1.28 (??0.15) consistent with grain boundary (Coble) diffusion creep. At low temperatures (T ≤ 700??C) coarse-grained dolomite exhibits higher strengths at higher temperatures which cannot be described by an Arrhenius relation, while fine-grained dolomite strengths show little or no temperature dependence. At high temperatures (T ≥ 800??C), dislocation creep of coarse-grained dolomite can be described by a thermally activated power law ⎟⎟⎠⎞⎜⎜⎝⎛−⎟⎟⎠⎞⎜⎜⎝⎛−=RTHno*31exp??σσεε&& with H*/n = 60 kJ/mol, or by an exponential law ()[]⎟⎟⎠⎞⎜⎜⎝⎛−−=RTHo*31expexpσσαεε&& with H*/α = 25447 kJ/mol. At high temperatures, diffusion creep of fine-grained synthetic dolomite can be described by ⎟⎟⎠⎞⎜⎜⎝⎛−⎟⎟⎠⎞⎜⎜⎝⎛−⎟⎠⎞⎜⎝⎛Ω=RTHdno*313exp??σσεε&& with H* = 280 ??45 kJ/mol. Taken together, the flow laws for coarse- and fine-grained dolomites constrain the high temperature conditions over which crystal plasticity, dislocation creep, and diffusion creep dominate.

Natural and hot isostatically pressed dolomite aggregates were experimentally deformed at effective pressures of Pe = 50 ?? 400 MPa, temperatures of 400 ?? 850??C, and strain rates of &#949;& = 1.2x10-4 s-1 to 1.2x10-7 s-1. Coarse- and fine-grained dolomite deformed at low temperature (T &#8804; 700??C for coarse-grained natural dolomite, T < 700??C for fine-grained natural and synthetic dolomite) exhibit mechanical behavior that is nearly plastic; differential stresses are insensitive to strain rate, fitted either by a power law no&#9119;&#9119;&#9120;&#9118;&#9116;&#9116;&#9117;&#9115;&#8722;=??&#963;&#963;&#949;&#949;31&& with n values that range from 12 to 49 or an exponential law ([31exp )] &#963;&#963;&#945;&#949;&#949;&#8722;=o&& with exponential law term &#945; values from 0.023 to 0.079 MPa-1. Microstructures of samples deformed at low temperatures include mechanical twins, and undulatory extinction suggesting that twin glide and dislocation slip are the predominant deformation mechanisms. At high temperatures (T &#8805; 800??C) flow strengths of coarse- and fine-grained dolomite depend more strongly on strain-rate and exhibit pronounced temperature dependencies. Microstructures of coarse-grained dolomite samples deformed at T &#8805; 800??C include undulatory extinction and fine recrystallized grains suggesting that recovery and dynamic recrystallization contribute to dislocation creep at these conditions. By comparison with lower temperature deformation, mechanical twinning is unimportant. Fine-grained synthetic dolomite deformed at high temperature (T &#8805; 700??C) exhibits nearly linear (Newtonian) viscous behavior, with n = 1.28 (??0.15) consistent with grain boundary (Coble) diffusion creep. At low temperatures (T &#8804; 700??C) coarse-grained dolomite exhibits higher strengths at higher temperatures which cannot be described by an Arrhenius relation, while fine-grained dolomite strengths show little or no temperature dependence. At high temperatures (T &#8805; 800??C), dislocation creep of coarse-grained dolomite can be described by a thermally activated power law &#9119;&#9119;&#9120;&#9118;&#9116;&#9116;&#9117;&#9115;&#8722;&#9119;&#9119;&#9120;&#9118;&#9116;&#9116;&#9117;&#9115;&#8722;=RTHno*31exp??&#963;&#963;&#949;&#949;&& with H*/n = 60 kJ/mol, or by an exponential law ()[]&#9119;&#9119;&#9120;&#9118;&#9116;&#9116;&#9117;&#9115;&#8722;&#8722;=RTHo*31expexp&#963;&#963;&#945;&#949;&#949;&& with H*/&#945; = 25447 kJ/mol. At high temperatures, diffusion creep of fine-grained synthetic dolomite can be described by &#9119;&#9119;&#9120;&#9118;&#9116;&#9116;&#9117;&#9115;&#8722;&#9119;&#9119;&#9120;&#9118;&#9116;&#9116;&#9117;&#9115;&#8722;&#9119;&#9120;&#9118;&#9116;&#9117;&#9115;&#8486;=RTHdno*313exp??&#963;&#963;&#949;&#949;&& with H* = 280 ??45 kJ/mol. Taken together, the flow laws for coarse- and fine-grained dolomites constrain the high temperature conditions over which crystal plasticity, dislocation creep, and diffusion creep dominate.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 97 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 82-87).

Syndepositional deformation features are fundamental components of carbonate platforms both in the subsurface and in seismic-scale field analogs. These deformation features are commonly opening-mode, solution-widened fractures that can evolve into extensional faults, and reactivate frequently through the evolution of the platform. They also have potential to behave as fluid flow conduits from the earliest phases of platform growth through burial and uplift, and can be active during hydrocarbon generation. As such, diagenetic alteration in the margins of these carbonate platforms is often intense, may demonstrate a preferential spatial relationship to the deformation features rather than the depositional fabrics of the strata, and may impact the permeability development of reservoir strata near deformation features. This study focuses on a syndepositional graben known as the Cave Graben fault system in the Yates Formation of Rattlesnake Canyon in the Guadalupe Mountains, and investigates the distribution of dolomite around the faults and associated opening-mode fractures, in an effort to understand the control the Cave Graben faults exert on fluid flow through the platform margins. Two generations of dolomite are identified on the outcrop: a fabric retentive dolomite located in the uppermost facies of the platform, and a fabric destructive dolomite that forms white, chalky haloes around syndepositional deformation features. The first generation of dolomite is dully luminescent and has very small crystal sizes, as well as a low trace element concentration and an ¹⁸O-enriched stable isotopic signature compared to Permian marine carbonate ratios. This dolomite is interpreted to have formed from the penecontemporaneous refluxing of concentrated lagoonal brine, and shows little fault control on its distribution. The second generation of dolomite is brightly luminescent and has much larger crystal sizes, as well as a higher trace element concentration and a slightly ¹⁸O-depleted isotopic signature compared to the first generation of dolomite, though it is still enriched in ¹⁸O compared to Permian marine carbonate. This dolomite is interpreted to have formed in a burial environment due to the transport of concentrated brines from the overlying evaporites through syndepositional deformation features. Overall, this study suggests that, once open, syndepositional deformation features may become the primary fluid conduit through otherwise impermeable strata, and may control the distribution of diagenetic products over a long period of geologic time. It provides valuable insight into the interaction of syndepositional faults and fractures and fluid flow, and may improve understanding of diagenesis in analogous subsurface carbonates reservoir intervals. / text

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Thesis (Ph. D.)--University of Wisconsin, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Sc.)(Environmental Geology)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.