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In this thesis, an integrated structural and chemical approach has been used to investigate the spatial and temporal evolution of fluid chemistry, and fluid flow pathways, during crustal shortening. The Taemas Vein Swarm is hosted in a limestone-shale sequence, the Murrumbidgee Group, in the Eastern Belt of the Lachlan Orogen, in New South Wales, Australia. The Taemas Vein Swarm (TVS) is composed of calcite ± quartz veins, hosted in a series of faults and fractures, which extends over an area of approximately 20 km2. The Murrumbidgee Group is composed of several formations, comprising massive grey micritic limestones, redbed sandstones and shales,and thinly interbedded (10–20 cm scale) limestones and shales. ¶ The sedimentary sequence has been folded into a series of upright, open to close folds, and was probably deformed during either mid-late Devonian, or early Carboniferous, crustal shortening. To the east, the Murrumbidgee Group is overthrust by a Silurian volcanic sedimentary sequence along the Deakin-Warroo Fault System. Crosscutting and overprinting relationships demonstrate that vein growth was synchronous with folding, with different vein types related to different fold mechanisms at various stages of fold growth. ¶ Flexural slip folding led to the development of bedding-concordant veins (hereafter called bedding-parallel veins). Flexural flow in semicompetent to incompetent beds caused en echelon extension vein arrays to grow. Decoupling between beds, and dilatancy at fold hinges led to significant vein growth. In addition, fold lock-up led to limb-parallel stretching, and the growth of bedding-orthogonal extension fractures. ¶ Vein growth is inferred to have occurred in a compressional tectonic regime (i.e. sigma3=vertical). Oxygen isotope quartz-calcite thermometry suggests that veins formed at temperatures of 100–200 oC. The depth of vein formation may have been between about 5 and 8 km. Vein textures indicate that growth of veins occurred during multiple cycles of permeability enhancement and destruction. Subhorizontal extension fractures, and faults at unfavourable angles for reactivation, imply that fluid pressures exceeded lithostatic levels during the growth of some veins. Coexisting extension and shear fractures imply that differential stress levels varied over time. ¶ Flexural slip continued throughout folding at Taemas, despite some fold limbs being at angles extremely unfavourable for reactivation ( > 60). As folds approached frictional lock-up, flexural slip continued to occur when supralithostatic fluid pressures were developed. Therefore, large, bedding-discordant faults were not developed to accommodate strain during folding, explaining a deficiency of larger faults in the TVS. ¶ Infiltration of overpressured fluids occurred into the base of the Murrumbidgee Group, and was channelled into a distributed mesh of small faults and fractures. At the point that a connected ‘backbone’ flow network developed in the TVS, highpressure fluids would no longer be available to allow continuing flexural slip on fold limbs approaching lockup. Thereafter, larger faults would develop, which would adjust the fault population in the TVS to a more ‘typical’ displacement-frequency distribution. This had not occurred in the Taemas area by the time crustal shortening ceased. An abundance of small faults, and fracturing driven by invasion of overpressured fluid, implies that the TVS formed via an ‘earthquake swarm’ process. ¶ Modern analytical techniques, utilising laser ablation sampling technology, allow high-spatial resolution chemical data to be collected from syntectonic veins. Insights into the role that fluid-mineral interface processes may have on the chemistry of minerals grown in syntectonic veins were provided by an experimental study. Moderate sized ( < 1−5 mm) synthetic calcite crystals were successfully grown to investigate the uptake of rare earth elements (REE) into calcite. Changes in crystal morphology are linked to variable solution chemistry, which has important implications for the interpretation of hydrothermal vein textures. High-spatial resolution chemical analyses of synthetic calcite crystals demonstrate significant fluctuations in REE concentrations over distances of < 200 μm within calcite crystals. Time-equivalent regions on different crystal faces have significantly different REE concentrations, indicating that fluctuations in calcite trace element composition cannot be interpreted exclusively in terms of changing ‘bulk fluid’ composition. Rare earth element anomalies (Eu/Eu* and Ce/Ce*) are not significantly influenced by compositional zoning, and may be robust indicators of changes in solution bulk chemistry and fluid oxidation state. ¶ Changes in isotopic ratios (13C, 18O and 87Sr/86Sr), and trace element concentrations in veins from the TVS are related to variations in fluid source, flow pathways and chemical conditions (e.g. trace element complexation, precipitation rate, fluid oxidation) during hydrothermal fluid flow. This integrated structural, textural and chemical approach has direct application to the examination of hydrothermal veins in fracture-hosted ore deposits, and may allow the fluid source and/or chemical conditions conducive to the formation of high-grade ore to be discerned. ¶ Vein 18O compositions systematically increase upwards through the Murrumbidgee Group, caused by progressive reaction of an externally derived, low-18O fluid (of probable meteoric origin) with host limestones. Vein 18O and 87Sr/86Sr compositions vary spatially and temporally within the same outcrop, and within individual veins, which is inferred to be caused by the ascent of packages of fluid along constantly changing flow pathways. Fluid-buffered oxygen isotope ratios at the earliest stages of deformation imply that the TVS formed via an ‘invasion percolation’ process. Fluid pathways are inferred to have changed constantly, with fractures ‘toggleswitching’ between high-permeability and low-permeability states, due to repeated fracture opening and sealing events.

I have studied syntectonic veins from shales and coarse calcareous sands of the Ordovician Womble Shale, Benton uplift, Arkansas. All veins are composed of calcite with minor quartz and trace feldspar and dolomite or high-Mg calcite in the coarser veins. All host lithologies have a pressure-solution cleavage, more closely spaced in the fine-grained shale beds. The vein internal fabrics are coarsely to finely fibered, with a strong host-rock grain size control on fiber width. The finest fibers are in veins with shale host and the coarsest in the coarse-grained calcareous sandstone. Fiber aspect ratio is inversely proportional to host grain size; more equant vein grains are found in the veins hosted in the coarse host fraction. Within one outcrop, the δ13C and δ18O compositions of the host lithologies range from 1.5 to -3.0 per mil and 7.5 to -14.0 per mil (VPDB), respectively. By contrast, the δ18O composition of the veins is remarkably constant (-13.5 per mil) among veins of starkly different fabrics. This composition is identical to that of the coarse calcareous sandstone lithology in the outcrop. No cathodoluminescence or stable isotope zoning was observed in the veins. In addition, there were no gradients in Ca or Si in the vicinity of the veins, suggesting either that the host did not contribute these elements or that diffusion was not the rate-limiting step to vein formation. In any case, the wide variety of veins was probably formed from meter-scale migration of fluid derived from local calcite-rich layers in calcareous sandstone.

The goal of this thesis is to provide a unified framework in which to analyze the dynamics of two seemingly unrelated families of one-dimensional dynamical systems, namely the family of quadratic polynomials and continued fractions. We develop a combinatorial calculus to describe the bifurcation set of both families and prove they are isomorphic. As a corollary, we establish a series of results describing the behavior of entropy as a function of the parameter. One of the most important applications is the relation between the topological entropy of quadratic polynomials and the Hausdorff dimension of sets of external rays landing on principal veins of the Mandelbrot set. / Mathematics

I have studied syntectonic veins from shales and coarse calcareous sands of the Ordovician Womble Shale, Benton uplift, Arkansas. All veins are composed of calcite with minor quartz and trace feldspar and dolomite or high-Mg calcite in the coarser veins. All host lithologies have a pressure-solution cleavage, more closely spaced in the fine-grained shale beds. The vein internal fabrics are coarsely to finely fibered, with a strong host-rock grain size control on fiber width. The finest fibers are in veins with shale host and the coarsest in the coarse-grained calcareous sandstone. Fiber aspect ratio is inversely proportional to host grain size; more equant vein grains are found in the veins hosted in the coarse host fraction. Within one outcrop, the δ13C and δ18O compositions of the host lithologies range from 1.5 to -3.0 per mil and 7.5 to -14.0 per mil (VPDB), respectively. By contrast, the δ18O composition of the veins is remarkably constant (-13.5 per mil) among veins of starkly different fabrics. This composition is identical to that of the coarse calcareous sandstone lithology in the outcrop. No cathodoluminescence or stable isotope zoning was observed in the veins. In addition, there were no gradients in Ca or Si in the vicinity of the veins, suggesting either that the host did not contribute these elements or that diffusion was not the rate-limiting step to vein formation. In any case, the wide variety of veins was probably formed from meter-scale migration of fluid derived from local calcite-rich layers in calcareous sandstone.

Akademisk avhandling--Göteborgs universitet. / Extra t.p. with thesis statement inserted. Bibliography: leaves 45-47.

Brick clay deposits, in the area north of Cape Town, were formed as a result of three independent geological processes. The intrusion of the syn- to post tectonic granitoids into micaceous (indicated by the absence of halloysite; Orris, 1998), feldspathic Malmesbury sandstone beds, approximately 500 Ma ago, created a hydrothermal vein structure, which enriched the shale with feldspar/kaolinite and quartz, restricted to the vein network. This was followed by extensive in-situ weathering of these hydrothermally altered rocks resulting in residual kaolin deposits, the effects of which were more pronounced along the more permeable shear zones. The final process, formation of ball clay deposits, initiated by the erosion of the primary kaolinite deposits, which have been transported in water, together with organic material, to shallow depressions where clays were deposited. Brick clay is exclusively used for the manufacturing of clay brick products and must derive its value from the sales revenue generated from these products. Evidence from the two exploration programs described, suggests that the clay deposits explored has no value as individual deposits as the clay from both deposits lack specific ceramic properties to successfully manufacture clay bricks. It is however clear that if the clay from the two deposits is mixed in specific proportions; body mixes with ceramic properties suitable for light coloured clay face brick manufacturing is possible. The value of the beneficiated product, clay bricks, may then be used to determine the value of both clay deposits. Discounted Cash Flow Models (DCFM) and Net Present Values (NPV) were used to determine the fundamental value of the clay deposits explored, as it determines the time value of money (Kernot, 1999). These models clearly showed the dependency of the value of clay brick deposits on variables such as raw material quality, capital expenditure and clay brick yields. Geological, chemical and ceramic knowledge of individual brick clay deposits and the management of the raw materials extracted from these deposits is key to the profitable manufacturing of clay bricks. Risks, at the quarrying level, related to these aspects need to be managed to ensure the profitable and efficient functioning of the entire brick production process. / Dissertation (MSc (Earth Science Practice and Management))--University of Pretoria, 2007. / Geology / MSc / unrestricted

Tungsten is listed on the European Commission list of critical raw materials that are crucial to Europe’s economy. By raising awareness of tungsten as a critical raw material the EU can prioritise to enhance exploration, mining and recycling of tungsten. In this thesis the structural relationship between wall rock and veins, in a greisen-tungsten vein deposit, were analysed with the intention to interpret how tectonic deformation events control the emplacement of tungsten-bearing veins. The objective of this thesis is to investigate if and how structures controlled hydrothermal fluid flow and ore formation in the Peña del Seo tungsten-greisen vein deposit. Greisen systems are associated with tin and tungsten-bearing minerals and are related to intrusive magmatic bodies of granitic composition. Greisen-related granites (leucogranites), form at shallow depths in the crust (1.5-4 km) generally in intracontinental tectonic settings such as orogenic belts. The study site is located in the West Asturian-Leonese Zone in northwest Spain. This zone marks the transition between the foreland and the hinterland and is recognized as being part of a continental margin, where Palaeozoic rocks were deposited unconformably. These rocks were subsequently subjected to folding during the Variscan orogeny (370-290 Ma). Three main types of structures were generated due to three deformational phases (D1, D2 and D3) during the Variscan orogeny. D1 resulted in east-verging recumbent folding and formation of a related axial-planar parallel cleavage (S1), D2 resulted in displacement along large thrust sheets and D3 produced upright folding and refolding of F1 folds. Geological mapping with a focus on structural geology was carried out in March 2019, covering an area of approximately 0.25 km2. Structural measurements and oriented rock samples for microstructural study in thin sections were collected in the field. Additionally, photogrammetric mapping of structures was performed on a 3D photogrammetry model derived from a UAS survey. The geometry of the Peña del Seo tungsten-greisen vein deposit is interpreted to result from two major deformation events. The axial planar foliation (S1) at Peña del Seo is correlated to the regional fabric that developed during D1 of the Variscan orogeny. The related F1 folds are caused by buckling accompanied by flexural slip folding mechanism during D1. Forceful intrusion of the granite underlying the Peña del Seo deposit caused bending of the overlying rocks layers during D2. Layer-parallel stretching is likely to have caused tension fractures perpendicular to bedding in the outer arc of the F2 fold hinge. The formation of local crenulation and related spaced cleavage can be explained by layer-parallel shortening in the inner arc of the F2-fold. Local transposition of S1-foliation occurred during emplacement of quartz veins and explains the different orientation of strike of foliation between the northern and southern parts of the area. Fractures forming during formation of F2-fold are likely to have worked as conduits for ascending hydrothermal, ore-bearing fluids forming the Peña del Seo tungsten-greisen vein deposit.

Deep Vein Thrombosis, a potentially fatal event, occurs when a blood clot forms within the deep veins of the body. This most frequently manifests in the lower extremities. The goal of this research was to build an inexpensive device that could apply therapeutic compressive pressure to the lower leg to aid in the prevention of deep vein thrombosis using only mechanical input from the user. Several different prototypes were designed and built with varying degrees of success. Characterization of the final prototype required calibration of pressure and force measurement sensors. Additionally, a mathematical model was developed in order to predict how changes in the design of the device, as well as differing sizes and shapes of lower legs, would impact the amount of applied pressure. The predictions of this mathematical model were found to be substantially larger when compared against empirical data. However, there is evidence to indicate that the final prototype could be minimally altered to apply ample therapeutic pressure. / Bioengineering