Thesis (Ph.D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 17, 2009). Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Neil Lundberg, Florida State University, College of Arts and Sciences, Dept. of Geological Sciences. Title and description from dissertation home page (viewed Mar. 2, 2004). Includes bibliographical references.

The development of an open pit mine at the Endeavour 42 (E42) epithermal gold deposit, situated in the Junee-Narromine Volcanic Belt of the Ordovician Macquarie Arc, central New South Wales, has provided a 3D view of the structurally controlled deposit which was hitherto not available due to the paucity of outcrop in the region. Outcropping geological relationships present a complicated history of overprinting structural deformation and vein events, including the spatial characterization of the gold-mineralizing system. Host rocks consisting of interbedded sedimentary and resedimented volcaniclastic facies, trachyandesite and porphyritic andesite lavas and intrusions (coherent and autoclastic facies), intruded by a large diorite sill, were initially tilted and faulted, followed by the emplacement of multiple dyke phases along faults. Economic gold mineralization at E42 is restricted to faults, fault-hosted breccias, and veins, and was deposited over a period spanning two distinct structural regimes. Early gold-bearing veins are steeply dipping and interpreted as forming coevally along two sets of faults and dykes within a tensional stress regime. High grade fault-hosted, hydrothermally cemented breccia intervals are included temporally with early gold-bearing veins based on comparable mineralogy and steep, fault parallel orientations. Crosscutting the early steep gold-bearing vein sets are two populations of coeval inclined gold-bearing veins, dipping moderately to the southwest and northwest, respectively, which formed in a compressional stress regime with tension directed subvertically. The E42 epithermal deposit likely developed in the period of overall crustal extension, ca. 443-433 Ma, following Phase 1 of the Late Ordovician – Early Silurian Benambran Orogeny. The generation of permeability, styles of fracture propagation, and the reactivation of pre-existing planes of weakness in the rock package are key factors in the development and current geometry of the E42 gold deposit. High grade veins and faults are commonly flanked by sericite-quartz ± carbonate alteration haloes, which exhibit consistent geochemical patterns for metals and pathfinder elements, both laterally away from structures, and vertically within the deposit. Au, Ag, As, Hg, Sb, Tl, Cu, Pb, and Zn, all display increasing concentrations towards high-grade structures, as well as higher up in the epithermal system, with varying dispersion haloes.

Syn-convergent low-angle normal-sense detachments (LANDs) are found in many orogens around the world. However, those tectonic processes which result in their formation are little known. The South Tibetan detachment system (STDS) is the best-studied example worldwide of a syn-convergent LAND, and formed in the Miocene due to the continental collision of India and Asia. In Bhutan, eastern Himalaya, the STDS is duplicated. Here I investigate the tectonic history of the inner STDS and particularly the outer STDS in Bhutan, to determine whether the duplicated STDS can be explained by or used to constrain models of Himalayan orogenesis. A range of geochronometric, thermochronologic, petrologic, structural, thermobarometric, thermometric, and isotopic tools are used to constrain: the onset and cessation of motion on the outer STDS; the cessation of motion on the inner STDS; the peak metamorphic conditions in the hanging wall and footwall of the outer STDS; the pressure-temperature-time paths of tectonites in the hanging wall and footwall of the outer STDS; the structural history of the hanging wall rocks of the outer STDS, and; the paleogeographic affinity of the hanging wall rocks of the outer STDS. The results of these studies are compared to thermo-mechanical models of Himalayan- type continental collision. Similarities in model predictions of the type and timing of structures, peak metamorphic conditions of hanging wall and footwall tectonites, pressure-temperature-time paths, and other regional tectonic observations lead to two main conclusions. 1. The STDS is a system of three main types of LANDs: those that formed during channel flow of low-viscosity mid-crustal rocks, those that formed by extrusion of cooled channel rocks to the surface, and those that formed by destabilization of the upper crust above a dome of mid-crustal channel rocks. 2. The STDS was duplicated by underthrusting of a crustal ramp into the Himalayan orogen since early Miocene. The underthrusting led to extrusion of a dome of weak mid-crustal above a previously-extruded channel. The crustal ramp may be local to the eastern Himalaya due to higher convergence and/or erosion rates, or due to local underthrusting of relatively strong crust behind weaker crust.

Understanding the development of the Himalaya is critical to elucidating continental collisional processes. The Greater Himalayan sequence (GHS), the exhumed mid-crust of the Himalayan orogen, records the tectonometamorphic evolution of the Himalaya from its deep hinterland to its foreland. The GHS in central Nepal and adjacent Tibet is deformed pervasively; quartz c-axis orientation fabrics from across the GHS indicate that it was deformed at high temperatures (~550-650˚C). The asymmetries of these quartz c-axis fabrics confirm field observations that define a reversal in shear sense from top-south shear near the bottom and middle of the GHS to top-north shear near the top of the package proximal to the South Tibetan detachment system (STDS). Estimates of mean kinematic vorticity from across the GHS indicate a pure shear contribution between 33% and 67%. U-Pb geochronologic data from the upper GHS exposed in the Changgo culmination in south Tibet indicate that melt crystallization and metamorphism related to crustal thickening occurred at ca. 35 Ma and was succeeded by a second metamorphic episode and syn-kinematic voluminous anatexis at ca. 22 Ma. The upper GHS was thinned vertically by 50% and extended horizontally during and immediately after the second metamorphic event, in a manner typical of the deep hinterland regions of orogens. In central Nepal, the ductile lateral extrusion of the upper GHS between the Main Central thrust (MCT) below and STDS above ceased by ~19 Ma. The cessation of lateral extrusion followed the collapse of the orogenic wedge and a reduction in the gravitational potential necessary to drive the propagation of deformation southwards towards the foreland. To restore the geometry of the wedge, deformation stepped out-of-sequence into southern Tibet, with the exhumation of the Changgo culmination and the North Himalayan antiform, before migrating incrementally back toward the foreland. Subsequently, the MCT migrated downward structurally adding material to the lower GHS as thrust slices, characteristic of foreland-style deformation. Thus, the transition between the upper and lower GHS in central Nepal records the transition from hinterland-style deformation to foreland-style deformation. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2009-04-13 11:48:45.702

The Southern Uplands of Scotland is interpreted as a Lower Palaeozoic accretionary complex which formed on the northern margin of the Iapetus Ocean. Seven conglomerates which contain detritus derived from the north-west, from sources on the Laurentian continental margin, were studied. Granite clasts in five of the conglomerates have distinct petrographic and geochemical characteristics which indicate that separate source areas supplied detritus to the Southern Uplands at different times. The Llandeilo Corsewall Point and Caradoc Glen Afton conglomerates, which occur in Tracts 1 and 2 of the Northern Belt, contain granite clasts that yield similar Rb-Sr whole-rock isochron ages (c. 1,200 Ma, 600-660 Ma and c. 475 Ma) and similar Sm-Nd model ages. This suggests that the clasts in the two conglomerates were derived from related sources. Some of the granite clasts in the early Ashgill Shinnel Formation conglomerate, which occurs in Tract 3 of the Northern Belt, resemble those in the Corsewall Point conglomerate, but most are petrographically and geochemically distinct, and yield younger Sm-Nd model ages. The lower Llandovery Pinstane Hill conglomerate occurs in Tract 4 of the Central Belt, and contains granitic detritus which yields a Rb-Sr whole-rock isochron age of 458 ± 26 Ma and has similar characteristics to the clasts in the Shinnel Formation conglomerate. The granite clasts in the Corsewall Point and Glen Afton conglomerates are of a different age to the granite intrusions of northern Scotland, and are unlikely to have been derived from this region. Conglomerates in the Midland Valley contain granite clasts with different petrographic and isotopic characteristics to those supplied to the Southern Uplands during the Llandeilo and Caradoc. However, north-west Newfoundland has a similar igneous history to that recorded by the Southern Uplands clasts, which could be derived from this region. The clasts supplied to the Shinnel Formation and Pinstane Hill conglomerates during the Ashgill and Llandovery have more in common with the granitic detritus in the Midland Valley. Thus, the Southern Uplands form a distinct Caledonian terrane which was south-east of Newfoundland in the Llandeilo, and was affected by sinistral strike-slip displacements during and after accretion.

The development of an open pit mine at the Endeavour 42 (E42) epithermal gold deposit, situated in the Junee-Narromine Volcanic Belt of the Ordovician Macquarie Arc, central New South Wales, has provided a 3D view of the structurally controlled deposit which was hitherto not available due to the paucity of outcrop in the region. Outcropping geological relationships present a complicated history of overprinting structural deformation and vein events, including the spatial characterization of the gold-mineralizing system. Host rocks consisting of interbedded sedimentary and resedimented volcaniclastic facies, trachyandesite and porphyritic andesite lavas and intrusions (coherent and autoclastic facies), intruded by a large diorite sill, were initially tilted and faulted, followed by the emplacement of multiple dyke phases along faults. Economic gold mineralization at E42 is restricted to faults, fault-hosted breccias, and veins, and was deposited over a period spanning two distinct structural regimes. Early gold-bearing veins are steeply dipping and interpreted as forming coevally along two sets of faults and dykes within a tensional stress regime. High grade fault-hosted, hydrothermally cemented breccia intervals are included temporally with early gold-bearing veins based on comparable mineralogy and steep, fault parallel orientations. Crosscutting the early steep gold-bearing vein sets are two populations of coeval inclined gold-bearing veins, dipping moderately to the southwest and northwest, respectively, which formed in a compressional stress regime with tension directed subvertically. The E42 epithermal deposit likely developed in the period of overall crustal extension, ca. 443-433 Ma, following Phase 1 of the Late Ordovician – Early Silurian Benambran Orogeny. The generation of permeability, styles of fracture propagation, and the reactivation of pre-existing planes of weakness in the rock package are key factors in the development and current geometry of the E42 gold deposit. High grade veins and faults are commonly flanked by sericite-quartz ± carbonate alteration haloes, which exhibit consistent geochemical patterns for metals and pathfinder elements, both laterally away from structures, and vertically within the deposit. Au, Ag, As, Hg, Sb, Tl, Cu, Pb, and Zn, all display increasing concentrations towards high-grade structures, as well as higher up in the epithermal system, with varying dispersion haloes.

Thesis (M.S.)--Ohio University, August, 2006. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy). Bibliography: leaves D40-D43.

Thesis (Ph.D.) -- Memorial University of Newfoundland, 1990. / Typescript. Bibliography: leaves 304-323. Also available online.