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Publication Open Access Vein textures at the Moss low-sulfidation epithermal gold deposit, Arizona: constraints on the processes of mineral deposition(Colorado School of Mines. Arthur Lakes Library, 2025)The Moss low-sulfidation epithermal deposit in the northern Oatman district in northwest Arizona formed as a result of the Miocene extension in the Colorado River extensional corridor. The main vein zone can be traced over a strike length of ~6.2 km although elevated precious metal grades occur primarily along a central, ~1.9 km-long segment. The vein zone crosscuts the medium-grained Moss monzonite and the Peach Springs Tuff, which was deposited during the 18.78 ± 0.02 Ma eruption of the Silver Creek Caldera. The highest precious metals grades occur where vein intersections contain dark gray bands of ore minerals, including native gold, acanthite, and silver sulfosalts. The ore minerals occur as dendritic aggregates hosted by a matrix of quartz that formed through recrystallization of a noncrystalline silica precursor originally deposited along vein walls and cementing wall rock clasts in breccias. Recrystallization of the noncrystalline silica matrix has progressed to completeness resulting in the development of characteristic quartz textures such as mosaic quartz characterized by interpenetrating grain boundaries and flamboyant quartz showing radiating arrays of inclusions. Prismatic quartz transected by recrystallization fronts containing abundant inclusions is common. The ore-bearing bands alternate with bands that contain bladed calcite. The texture of the calcite is inconsistent with calcite growth in open space. Similar to the ore mineral dendrites, the textural evidence suggests that the calcite blades grew in the gel-like silica matrix. This type of calcite is texturally distinct from lattice-bladed calcite in which polyhedral cavities separate blades. Microthermometric investigations suggest that calcite deposition occurred at ~265°C at approximately 600 m below the paleosurface. It is proposed here that ore mineral formation and the growth of calcite in the noncrystalline silica precursor took place during short-lived events of fluid flashing at far-from-equilibrium conditions. The amount of vapor present during flashing presumably played a key control on mineral precipitation and growth.Publication Open Access Additive manufacturing framework, and cost evaluation tool for use in the cis-lunar ecosystem, An(Colorado School of Mines. Arthur Lakes Library, 2025)Manufacturing and construction on the lunar surface will heavily depend on lunar regolith. Regolith can serve as a feedstock in various additive manufacturing technologies to create equipment for use within lunar habitats. The costs associated with lunar additive manufacturing are influenced by both the printing location and the feedstock source. Therefore, there is a need for a method to predict costs for additive manufacturing during various operational stages. This thesis consists of two major topics related to lunar regolith. The first presents research on a terramechanics study on the excavation forces required to mine regolith for subsequent use in additive manufacturing. The second is the development of a comprehensive AM framework, complete with a custom-built Cost Estimation Tool (CET) model. The terramechanics study describes experimental and analytical work, evaluating the effect of lunar agglutinates on bulk regolith simulant properties. Three predictive terramechanics models were employed to compare the predicted horizontal excavation forces to measured values in atmosphere and vacuum conditions. The introduction of agglutinates increased the excavation forces when measured during a shallow, vertical blade cut. The AM framework developed in this thesis outlines the progression of AM usage through four stages, with each stage representing an increase in technological capability. The CET model improves modern AM costing tools by incorporating machine-specific parameters and simulation-driven design. Results show cost-per-part savings utilizing AM on the lunar surface when leveraging fully in-situ based feedstock compared to terrestrially based manufacturing and shipment of parts to the Moon. Furthermore, the AM framework illustrates the viability of ISRU-produced components, which have undergone minimal post-processing. This reduces the total cost of potential components such as building materials or rover equipment.Publication Open Access Measurement system for in situ application of strain in silicon and silicon–germanium quantum dots, A(Colorado School of Mines. Arthur Lakes Library, 2025)Engineering tunable valley splitting in silicon/silicon–germanium quantum-dot spin qubits is a central route to suppressing spin–valley leakage, minimizing charge-noise sensitivity, and extending coherence times to the fault-tolerant regime. Here we develop and characterize a cryogenic measurement platform to engineer this valley splitting via uniaxial strain applied in situ to foundry-fabricated Tunnel Falls qubit chips. Strain is transferred through commercial longitudinal piezoelectric actuators and calibrated with four-wire measurement and a temperature-compensated Wheatstone bridge employing modified-Karma nickel–chromium gauges. Four-wire resistance and balanced-bridge readouts enable microstrain resolution from a room-temperature environment down to cryogenic temperatures. Thermal and mechanical anchoring of the actuators to a stage presents challenges to prevent restriction of the actuator stroke and hence the applied strain. We design a two-piece stage that allows for easy loading of the actuators into a dilution refrigerator while providing the required anchoring. Finite-element simulations of the stage predict suppression of stray electrostatic fields by more than one order of magnitude at the device surface, helping to ensure that gate-defined potentials remain unperturbed while the crystal lattice is distorted. Our platform enables quantitative tests of deformation-potential and interface-roughness theories that predict how strain modifies the valley–orbit coupling parameter and, consequently, the spin relaxation and coherence times. Utilizing electrically driven strain therefore opens a path toward large, tunable valley splitting, important for future large-scale CMOS-compatible quantum processors.Publication Open Access Effects of nitrogen, ferrite morphology, and texture evolution on impact toughness in heat-affected zone simulations of V-microalloyed HSLA steel welds(Colorado School of Mines. Arthur Lakes Library, 2025)Microalloyed HSLA steels are used in lower-operating temperature structural applications, including bridges and pipelines, due to the wide range of achievable strength and toughness values obtained in the as-rolled products. However, the low temperature toughness associated with welds in high-impact applications remains an opportunity for improvement due to the tendency to form lower-toughness microconstituents such as bainite. Acicular ferrite (AF) is being investigated as a microconstituent to improve low temperature impact toughness in the coarse-grained heat affected zone of welds while maintaining required tensile strength levels for such applications. In this study, peak temperature and cooling rate were varied to simulate different HAZ regions in two experimental V-microalloyed steels differing in N content to produce microstructures with various ferritic microconstituents. Two alloys of different N contents of 80 and 200 ppm were utilized to change the volume fraction of VN precipitates in the microstructure. Optical microscopy and crystallographic analysis using EBSD were utilized to differentiate between the ferritic microconstituents and quantify microstructural evolution with processing parameters. A shift from primary ferrite to martensite/bainite microstructures was observed with increasing cooling rate at both peak temperatures selected for continuous cooling behavior analysis. Greater N content was associated with more grain-boundary ferrite. Crystallographic analysis further supported a shift towards a more displacive nature of the developed ferrite microconstituent with increasing cooling rate. The hardness increased as cooling rate increased due to less primary ferrite, with the alloy containing more N producing greater hardness values in all conditions as a result of grain refinement and a higher fraction of high dislocation density microconstituents, such as bainite. A higher N content produced finer prior-austenite grains at every cooling rate, yielding greater amounts of grain-boundary ferrite morphologies. Charpy impact toughness at -20 °C increased as cooling rate increased for both alloys in AF-predominant conditions due to the reduction in grain-boundary ferrite amount and effective ferrite grain size. A lower N content was associated with enhanced low-temperature toughness at every cooling rate due to less grain-boundary ferrite.Publication Open Access Multi-scale evaluation of groundwater flow and metal sourcing to streams in the Bonita Peak mining district(Colorado School of Mines. Arthur Lakes Library, 2025)Hydrologic and geochemical processes associated with acid mine drainage that result in the weathering of sulfide minerals and fluxes of metals to streams vary through space and time. Remediation of former mine sites relies on appropriate recognition and quantification of these changing processes. The need for both conceptual and quantitative understanding is particularly acute in headwater streams because these watersheds generate much of the water essential for ecosystem function and downstream human use, and headwater regions may be particularly sensitive to climatic changes. This research focuses on the Upper Animas River watershed in southwestern Colorado, a region substantially affected by historical mining over the past nearly 150 years to identify processes governing groundwater recharge and movement to streams, and associated metal weathering and fluxes, that operate over orders of magnitude in spatial and temporal extent. The three primary conclusions of this research are 1) metals are sourced from weathering of mineral deposits at depth (>500 meters below ground surface) and are transported long distances (multiple kilometers) by deep groundwater flow paths that terminate at springs and draining mines; 2) groundwater flow paths were modified by emplacement of hydraulic bulkheads resulting in new mineral equilibrium controls within the subsurface and a net decrease in iron and zinc export from the watershed; and 3) the solute budget of streams is controlled by discharge and metal fluxes from multiple distinctive groundwater systems with unique geochemical compositions and timescales of response to climatic perturbations. These results illustrate that groundwater flow, groundwater/surface-water interactions, and metal fluxes vary over spatial extents ranging from meters to multiple kilometers and on timescales ranging from days to decades. Data collection and modeling approaches that account for dynamic systems over these ranges of spatial and temporal extent are necessary when studying mountain headwater regions.