No description available.

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2003. / Vita. Includes bibliographical references.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / The ca. 36 Ma Chesapeake Bay impact event on the east coast of Virginia, USA, formed an 85 km complex crater in Cretaceous to Eocene sediments and underlying crystalline basement rocks belonging to the Appalachian orogen. Appalachian rocks are well exposed along the Appalachian Mountains to the west, however, little is known of the basement along the Atlantic Coastal Plain owing to the covering sedimentary sequence. This study investigates the crystalline rocks intersected by the 2006 ICDP (International Continental Scientific Drilling Program) – USGS (United States Geological Survey) drilling of the Chesapeake Bay impact structure (CBIS) on the Eyreville Farm near Cape Charles, Virginia. The crystalline rocks of the Eyreville-B borehole core are found in the lower basement-derived section (between 1551.19 m and 1766.32 m depth), in the amphibolite megablock (between 1376.38 m and 1389.35 m depth) and in the upper granite megablock (between 1095.74 m and 1371.11 m depth). The lower basement-derived section consists of foliated metasediments, which include mica schist, amphibolite and calc-silicate rock, and coarse-grained to pegmatitic granite. The amphibolite megablock is a black to dark grey to dark green, fine- to medium-grained, locally foliated, relatively homogenous, lithic block. The upper granite megablock is divided into gneissic and massive varieties, with a minor component of biotite schist xenoliths. The crystalline rocks contain foliations and related structures, fractures and breccias, microstructures and porphyroblast microstructures; however, none of the three lithic blocks is in situ and, consequently, structural measurements cannot be fully interpreted tectonically. Mineral assemblages and microstructural evidence in the mica schists suggest the rocks in the lower basement-derived section experienced a syn-D1 amphibolite facies peak metamorphic event (M1a) followed by retrograde metamorphic conditions (M1b) limited to D1b mylonitic and D2 brittle deformation. Similar metamorphic conditions in the upper megablocks suggest that the three sections likely formed part of a single metamorphic terrane. iv Geochemistry in the lower basement-derived mica schists revealed a strong intermediate igneous provenance, whereas the upper megablock biotite schist xenoliths showed a quartzose sedimentary provenance; the precursors to both appear to have been deposited in active continental margin settings. The lower basement-derived amphibolite appears to be derived from a sedimentary source. The precursor to the upper amphibolite megablock, on the other hand, was probably a tholeittic gabbro generated in an island arc setting. The peraluminous, S-type nature of the lower basement-derived granite suggests it was most likely generated in a within-plate tectonic setting. In contrast, the massive and gneissic granites from the upper megablock are metaluminous, I-type granites that were most likely generated in a syn-collisional environment. Metamorphic conditions of the M1 event were constrained using mineral assemblages mainly from the lower basement-derived section, which limited the X(H2O) value to 0.8, P to >0.4 GPa and the T range to 600-670°C. Using the 0.4 GPa pressure constraint, Zr-in-rutile thermometry revealed a peak metamorphic temperature for the M1 event of 606 ± 18°C, which is consistent with mid-amphibolite facies metamorphism. These estimates suggest a very steep geothermal gradient approaching ~44°C/km. Rutile U/Pb geochronology revealed that the M1 event recorded in the lower basement-derived metasediments occurred at 259 ± 13 Ma, with Ar/Ar geochronology indicating the cooling path through to greenschist metamorphic conditions. Zircon U/Pb SHRIMP geochronology performed by Horton et al. (2009b) on the massive and gneissic megablock granites dated their crystallisation ages at 254 ± 3 Ma and 615 ± 7 Ma, respectively, with the former age in agreement with the rutile U/Pb peak metamorphism results from the lower basement-derived section. These ages, together with petrography, structural observations, geochemistry and geothermobarometry suggests that the amphibolite and granite megablocks form part of the same metamorphic terrane as the lower basement-derived section and that the D1 and M1 events recorded in the lower basement-derived section and upper megablocks of the Eyreville-B borehole core likely occurred during the late stages of the Alleghanian orogeny. v Based on mineralogy, geochemistry, metamorphic grade and structural evidence, comparisons with the neighbouring terranes within the Appalachian basement beneath the Atlantic Coastal Plain sediments suggest that the lower basement-derived and upper amphibolite and granite megablocks of the Eyreville-B borehole core most likely formed part of the Hatteras terrane prior to the Chesapeake Bay impact event. This terrane, together with 5 other terranes, forms part of the Carolina Zone, a peri-Gondwanan micro-continent formed by the amalgamation of magmatic arcs during the Penobscottian and Taconian orogenies, which was then accreted onto the Laurentian margin during the Salinic and Acadian orogenies.

Inaug.-Diss.-Münster (Westf.). / Lebenslauf. Includes bibliographical references (p. [7]).

Photocopy of typescript. / Digitized by Kansas Correctional Industries

No description available.

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2003. / Title from title page screen (viewed Nov. 11, 2003). Thesis advisor: Robert D. Hatcher. Document formatted into pages (xiii, 296 p. : col. ill., col. maps). Vita. Includes bibliographical references.

Orientador: Norberto Morales / Banca: Antonio Roberto Saad / Banca: Eduardo Salamuni / Banca: José Luiz Albuquerque Filho / Banca: Sueli Yoshinaga Pereira / O uso intenso e a poluição dos recursos hídricos superficiais na bacia do rio Jundiaí têm levado à busca acelerada por recursos hídricos subterrâneos. A maior parte da bacia se situa sobre o Embasamento Cristalino, onde o fluxo subterrâneo é condicionado pela presença de descontinuidades. Para investigar o comportamento da água subterrânea neste contexto é necessária, além da caracterização hidrogeológica, a definição das características geológico-estruturais e tectônicas da área. Além do Sistema Aqüífero Cristalino, a bacia envolve também o Sistema Aqüífero Tubarão, situado no lado oeste da área, e o Sistema Aqüífero Cenozóico, distribuído ao longo das drenagens principais. Identifica-se um importante controle estrutural sobre a produtividade dos poços, não só daqueles que explotam as rochas cristalinas, mas também dos que captam água das rochas sedimentares. A integração de dados geológico-estruturais e hidrogeológicos indica que o controle estrutural ocorre principalmente em zonas de abertura, onde esforços transtrativos induzem a formação e/ou reativação de estruturas rúpteis de direção NW-SE e E-W, comumente associadas à presença de depósitos aluviais. Outros fatores de interferência também foram identificados, como a localização dos poços em relação à compartimentação morfoestrutural da área e a superexplotação dos aqüíferos, que, ao contrário daquelas estruturas, tende a diminuir a produtividade dos poços. / The intensive use and pollution of superficial water resources in the Jundiaí River Catchment lead to an increasing groundwater exploitation. The major part of Jundiaí Catchment is located on the Crystalline Basement, where water flow is dependent on discontinuities. In order to investigate the behavior of groundwater in such a context, it is necessary, besides the hydrogeologic characterization, the definition of geologic, structural and tectonic characteristics. The Tubarão Aquifer System occurs on the west side of the area and the Cenozoic Aquifer System is distributed along the main channels. It is possible to identify an important structural control over well productivity, not only on those located in crystalline rocks, but also on those located in sedimentary rocks. The integration of geologic, structural and hydrogeologic data shows that structural control happens mainly in distensive areas, where transtractive tension leads to formation and/or reactivation of brittle NW-SE and E-W structures, commonly associated with the occurrences of alluvial deposits. Other factors that affect well productivity were identified, for example, the location of wells with respect to some morphostructural compartments and the overexploitation of groundwater, which, despite favorable geologic structures, tend to decrease well productivity. / Doutor

The Sacramento Mountains, a metamorphic core complex that lies in the Colorado River extensional corridor of southeastern California, contains complex lithologic and structural relationships. Detailed mapping and petrographic analysis of lower plate rocks from the central part of the range show that three deformation events have been recorded. An amphibolite facies-grade foliation (Sg), which represents the oldest deformational event (D1), is the predominant fabric in the quartzofeldspathic country rock (grey gneiss). The second deformational event (D2) produced a variably developed greenschist facies-grade fabric (Sm) in the grey gneiss and in two post-D1 plutonic suites. Both of these plutons are thought to be Cretaceous or Tertiary in age. Variations in mylonitic development throughout the lower plate can be attributed to the ratio of strong minerals to weak minerals. Those with high strong-to-weak ratios (eg. granodiorite, diorite, tonalite, quartz diorite) do not form foliations as easily as rocks with low strong-to-weak ratios (eg. granite). This results in a diffuse distribution of mylonitic fabrics and many small scale shear zone boundaries. There is no evidence, however, for a major shear zone boundary (mylonitic front) in the Sacramento Mountains. Northeastward-directed Tertiary extension (D3) resulted in development of multiple high-angle and low-angle faults within and adjacent to the lower plate. Chloritic breccia is found along many of these faults and always cross-cuts the mylonitic fabric. Stage 1 of chloritic breccia evolution was the development of low-angle brittle shear zones and oblique fractures, and was accompanied by deposition of cryptocrystalline epidote. Stage 2 was the formation of conjugate fracture sets at a high-angle to the brittle shear zone accompanied by precipitation of chlorite as well as epidote and other propylitic minerals. Evidence for the importance of both high- and low-angle faulting during the structural evolution of the Sacramento Mountains is found in the many faults both within and adjacent to the lower plate. The upper and lower plates are separated by the Sacramento fault system that includes gently, moderately, and steeply dipping, dip-slip to oblique-slip fault segments. Recent models of core complex development hint at the complexity of fault systems and recognize the importance of high-angle faulting in upper plate rocks. However, most lower plate structures are attributed to low-angle faulting and folding of the fault surface. In the Sacramento Mountains, the lack of evidence for folding of the lower plate plus the development of multiple subvertical faults, both within and between plates, suggests that high-angle faulting was important throughout the evolution of the core complex, and not just in the final stages. / Ph. D.

The Striped Rock pluton of the late-Proterozoic Crossnore Plutonic-Volcanic suite is located beneath the Fries Thrust zone in the Blue Ridge province of southwest Virginia. The multiphase granite pluton has been affected by episodes of brittle and crystal plastic deformation at both the microscopic and mesoscopic scales. Brittle deformation preceded and postdated crystal plastic deformation. The pluton is cut by pervasive centimeter-scale cataclasite zones and ductile shear zones that vary in width from a few millimeters to several hundred meters. The majority of mylonite zones in the pluton strike east and northeast and are inclined moderately southeast. Cataclasite zones strike northeast and northwest. Deformation is most intense along the southern contact with the Cranberry gneiss where both pluton and country rock are deformed into a northeast-striking zone of mylonitic augen gneiss. The intensity of deformation decreases northwestward. Southeastdirected normal fault displacement is common to east and northeast-trending shear zones. A minor group of northwest-oriented shear zones dip moderately southwest and northeast and show sinistral, strike-slip displacement. Quartz-, chlorite- and stilpnomelane-filled cracks and veins with northeast and northwest trend uniformly overprint mylonite and cataclasite zones of all scales. Microstructure changes progressively with increasing strain. Feldspar grains are cut by at least two generations of mineralized, dilatant microcracks. Minerals precipitated in the early set of microcracks have undergone extensive crystal plastic deformation. Late-stage microcracks are filled with completely undeformed minerals. The spatial distribution of normal fault mylonite zones is geometrically consistent with generation during 1) late-Proterozoic extension, 2) Mesozoic extension, 3) rigid-body rotation during Paleozoic thrusting, or 4) "gravitational collapse" during Paleozoic thrusting. Field and microstructural evidence favor (4). The exact timing of deformation is not, however, well-constrained. / Master of Science