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

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

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: leaf 238-250.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 26, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Mian Liu. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 114-131).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Mar. 4, 2009). Includes bibliographical references (p. 50-59).

No description available.

Le gisement nickélifère latéritique de Nouvelle-Calédonie, développé au toit de la Nappe des Péridotites, représente près de 20% des ressources mondiales en nickel. Afin de mieux comprendre la formation de ce gisement, notre étude, portant sur le massif de Koniambo, se singularise par la volonté de ne pas se focaliser uniquement sur la zone minéralisée. L’approche employée a combiné : i) l’analyse de la déformation interne de l’ensemble du massif, ii) la caractérisation isotopique de deux sous-produits supposés de l’altération supergène que ont les veines de quartz et les veines de magnésite, iii) la modélisation 3D du gisement nickélifère, basée sur les données de plus de 6000 forages de subsurface et sur l’étude d’affleurements ponctuels au sein de la zone minéralisée. L’évolution spatiale et temporelle de la déformation associée à la serpentinisation est décrite au travers des ~800 m d’épaisseur structurale du massif de Koniambo. La partie supérieure du massif, très fracturée, préserve la marque d’au moins deux événements précoces de déformation. Le premier est associé au réseau de failles à antigorite et le second au réseau de failles à serpentine polygonale. La semelle serpentineuse, épaisse de ~200 m, est constituée de brèches et mylonites et enregistre un cisaillement tangentiel diffus associé à la serpentine polygonale et à la magnésite. La semelle représente ainsi un niveau de décollement majeur en base de nappe. Entre la semelle et le haut du massif, un niveau intermédiaire est identifié, caractérisé par la présence de zones de cisaillement plurimétriques probablement connectées à la semelle. La caractérisation 3D de la distribution du nickelau sein du niveau saprolitique, à l’échelle du gisement comme à l’échelle de l’affleurement, permetde mettre en évidence l’existence de processus impliquant une redistribution non pas seulement verticale, comme il est classiquement admis, mais aussi latérale, mécanique ou associée à des fluides, à l’origine d’importants enrichissements locaux. L’analyse isotopique des veines de quartz associées au minerai garniéritique met en évidence les conditions d’hydrothermalisme de basse température associées à leur formation. La caractérisation structurale et isotopique (couplage ''isotopes stables'' et ''clumped isotope thermometry'') des veines de magnésite situées dans la semelle serpentineuse permet de documenter leur caractère syn-tectonique et la nature météorique et de basse température du fluide dont elles sont issues. Ceci nous amène à proposer que la tectonique active a pu faciliter l’infiltration de l’eau météorique impliquée dans le processus de latérisation depuis le sommet jusqu’à la base de la nappe. / The New Caledonia nickel laterite ore deposit, developed at the top of the Peridotite Nappe, hosts about 20% of the nickel resources worldwide. In order to better understand the formation of this eposit, our study, focusing on the Koniambo Massif, is not restricted to the ore zone but concerned with the whole peridotite pile. Our approach combined: i) the analysis of the internal deformation of the massif, ii) the isotopic characterization of quartz and magnesite veins which are suspected to represent by-products of the laterization process, iii) the 3D modelling of the lateritenickel ore deposit, based on a dataset of ~6000 subsurface boreholes and the study of some outcrops located into the mineralized area. The spatial and temporal evolution of the deformation associated with serpentinization is described across the ~800 m-thick rock pile of the Koniambo Massif. The upper part of the massif is densely faulted and preserves the record of two early deformation events. The first one is associated with synantigorite faults and the second one with syn-polygonal serpentine faults. The ~200m-thick serpentine sole is composed of breccias and mylonites and records pervasive tangential shearing associated with polygonal serpentine and magnesite. Thus, the serpentine sole represents a major décollement at the base of the nappe. Between the sole and the upper part of the massif, anintermediate structural level is identified, characterized by the presence of plurimetric shear zones that probably merge with the sole.The 3D characterization of the nickel distribution in the saprolite level, at both deposit and outcrop scales, gives evidence for processes implying not only vertical (as commonly assumed) but also lateral nickel redistribution. This lateral transport ismechanical or associated with fluids and leads to significant local enrichments. The isotopic characterization of the quartz veins associated with garnieritic ore shows that they formed under low temperature hydrothermal conditions. The structural and isotopic (coupling “stable isotope” and “clumped isotope thermometry”) characterization of the magnesite veins located at the serpentine sole shows that they are syn-tectonic and derived from low temperature meteoric water. As a result, we propose that active tectonics has enhanced the infiltration of the meteoric waters involved in the laterization process down to the base of the nappe.

Detailed structural and petrologic mapping near Azure Lake, British Columbia provides an overview of geologic relations along the northeast margin of the Shuswap Metamorphic Complex. Four phases of deformation have been recognized in the Shuswap Complex and the adjacent lower grade metasediments of the cover sequence. The first deformation consists of west-verging isoclinal folds plunging north and northwest. The second phase resulted in large upright folds with a shallow northwest or southeast plunge. The third and fourth phases are only locally developed as faults, fractures, and brittle folds trending north and northeast, respectively. Mineral assemblages range from garnet-biotite through first sillimanite zones of the Barrovian facies series. Metamorphic grade increases toward the southwest. Regional metamorphism is associated with the first phase of deformation. The Complex is separated from the adjacent cover sequence by a first phase tectonic slide. Structural and metamorphic discontinuities across this slide probably resulted from reactivation of the slide surface during the second phase of deformation. Microprobe analyses have been combined with linear regression techniques to outline probable sillimanite-forming reactions in pelites of the Complex. The regressions show that reaction textures are partly preserved because of the exhaustion of rutile as a reactant phase. Metamorphic conditions in the Complex are estimated from the mutual intersection of experimentally studied mineral equilibria. These conditions are: P=7600 ± 400 bars, T=705 ± 40°C, aH₂O =0.5 ⁺⁰•⁵­₀․₂ . Carbonate mineral assemblages initially buffered fluid phase compositions to high X CO₂ values near 0.75 during metamorphism. Therefore the fluid phase was not homogeneous in composition throughout all rock types during metamorphism. Whole rock Rb-Sr dates of 138 ± 12 Ma (all five samples) and 163 ± 7 Ma were obtained for granodiorite stocks in the Azure Lake area. Two biotite-whole rock ± hornblende dates of 119 ± 11 Ma and 77 ± 20 Ma indicate isotopic resetting. Initial Sr⁸⁷ -Sr⁸⁶ ratios vary from 0.7061 ± 0.0001 to 0.7103 ± 0.0002 for rock and mineral dates. These dated stocks cross-cut structural trends for the first two deformations and impose a hornfelsic contact aureole on regional metamorphic assemblages. Therefore regional metamorphism and deformation were completed by Late Jurassic time. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate