Thesis advisor: Ethan F. Baxter / Spiral garnets are well-documented metamorphic microstructures that have been observed in orogens throughout the world. The preferred orientation of spiral garnet axes has been proposed (Bell and Johnson, 1989) to record and preserve information about the timing, rate, and orientation of the tectonic-scale processes. Using the model of Be Spiral garnets are well-documented metamorphic microstructures that have been observed in orogens throughout the world. The preferred orientation of spiral garnet axes has been proposed (Bell and Johnson, 1989) to record and preserve information about the timing, rate, and orientation of the tectonic-scale processes. Using the model of Bell and Johnson (1989), Aerden et al. (2013) proposed a link between the preferred orientation of spiral garnets and changes in relative plate motion between Iberia and Africa. The goal of this thesis is to this relationship by absolutely dating, eight samples from the Betic-Rif arc with measurable spiral axis orientations were chosen for Sm-Nd garnet geochronology. Chapter one is a detailed literature review of prior work on the formation and interpretation of spiral garnets. In chapter two we present 11 bulk Sm-Nd garnet ages from eight samples, these ages range from 35.6 ± 2.8 to 13.62 ± 0.69 Ma. The results from the obtained bulk garnet ages reveal a more complex relationship between FIA orientations and plate motion that originally hypothesized in Aerden et al. (2013). Large-scale rigid block rotations that postdate garnet growth may have influenced the current orientation of FIA from the western Betic-Rif. In chapter three, zoned geochronology was conducted on a single sample from the Nevado-Filabride Complex. This study revealed spiral garnet formation occurring on a rapid timescale, just 〖0.45〗_(-0.32)^(+0.51) Myr. While other zoned garnet studies have shown similar rapid growth in subduction zone setting (Dragovic et al., 2012), this is the first such documentation of such rapid growth from a garnet hosting spiral inclusion trails in a regional metamorphic setting. We calculated strain rates considering different genetic models for the spiral inclusion trails either by garnet rotation in simple shear, or by episodic overgrowth of suborthogonal crenulation cleavages due to switching stress axes. In both cases a similar fast strain rate of ca. 10-13 s-1 was obtained, which is an order of magnitude faster than typical regional strain rates and faster than previous spiral garnet studies regardless of the method used to calculate strain-rate. / Thesis (MS) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Thesis advisor: Amy E. Frappier / A ~7,000 year stable isotope record from a Central American stalagmite is presented as a record of rainfall and consequently Intertropical Convergence Zone (ITCZ) tropical rain belt strength over the late Pleistocene to mid-Holocene. The "amount effect" explains the well-documented inverse relationship between rainfall amount and stable oxygen isotope values observed in tropical monsoon regions and consequently in stalagmite calcite from those regions. ITCZ rainfall influences much of the Central American tropical region and here a ~7,000 year stable isotope record from stalagmite ATM1 harvested from Actún Tunichil Muknal Cave in Belize is presented as a record of ITCZ influenced rainfall during the late Pleistocene to mid-Holocene (5,561 ± 2,488 BP - 12,605 ± 284 BP). Three major oxygen isotope excursions occur within the record. These excursions correspond to the global cold Younger Dryas and 8.2 ka events and a relatively undocumented wet period around 6,300 bp. The Younger Dryas manifests as a relatively moist period in central Belize while the 8.2 ka event manifests as a relatively dry period. The reason for the opposite responses to cooling elsewhere in the globe is posited to be due to orbital forcings. The 6,300 bp relatively wet period appears to be synoptic in scale and two possible triggers for the isotope excursion are presented: eustatic sea level rise causing lagoonal constriction, warming of water off the coast of Belize, and thus increased evaporation and precipitation over the study region; and hurricane clusters, evidenced in the region in the succeeding 1,000 years, in which the location of the Azores High funnels hurricanes to make landfall near the central Belize region. ATM1 provides evidence for tropical leads and/or lags to global climate events and bolsters the idea that high and low latitude climate relationships are complexly interlinked. / Thesis (MS) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Thesis advisor: Rudolph Hon / In the northeast United States, arsenic (As) contamination in groundwater is frequently associated with historical landfill leachate plumes. Based on the history of Shepley's Hill Landfill (SHL) in Devens, MA, solid waste disposal activities spanned nearly a century of landfilling with little or no documentation of when or what waste material was disposed. Past geochemical investigations proved the presence of high levels of As in groundwaters within and around the SHL region. A total of 114 samples were collected from the SHL region and analyzed for their hydrogeochemistry and isotopic signature. Since the isotopic ratios of äD and ä18O can potentially be influenced by the mobilization process of As, this study attempts to identify any correlations between the stable isotopic ratios and the hydrogeochemistry of SHL waters. The results of the groundwater hydrogeochemical analysis show multiple relationships between metal concentrations and As concentration levels, typical of groundwater undergoing redox reactions. The result of the stable isotope analysis show significant fractionation of stable isotope ratios away from the meteoric water line. However, the role of strong redox gradients and various redox ladder reactions involving water did not produce a significant correlation with the isotopic fractionations present within different zones of the landfill. In most cases, the fractionations stand independent of the increase/decrease in As concentration and can be attributed to either unrelated chemical reactions within groundwater or evaporation. / Thesis (MS) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

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Orientador: Carlos Ducatti / Banca: José Roberto Sartori / Banca: Alfredo Sampaio Carrijo / Resumo: Este trabalho objetivou determinar o turnover do carbono-13 no Pectoralis major, quilha, tíbia e fígado de frangos de corte em diferentes períodos de crescimento, utilizando a técnica de isótopos estáveis. Foram utilizados 184 pintos de corte, machos, Cobb, distribuídos ao acaso em sete tratamentos com dias de substituição das dietas distintos: 0; 7; 14; 21; 28; 35; 42 dias de idade, denominados: T0-14, T7-21, T14-28, T21-35, T28-42, T35-49 e T42-56 respectivamente. Para mensurar o turnover do carbono-13 (diluição isotópica) nos tecidos em determinado intervalo de tempo, foram utilizados o modelo sigmoidal de regressão de Boltzmann ou função exponencial do tempo. Os valores de meias-vidas foram: 2,5; 2,8; 2,9; 4,9; 5,1; 5,5 e 6,0 dias para músculo peitoral; 2,7; 2,9; 3,1; 4,6; 5,3; 4,1 e 8,0 dias para quilha; 4,4; 3,6; 5,4; 5,8; 4,3; 5,2 e 6,3 dias para tíbia e 1,3; 1,9; 1,4; 1,5; 1,9; 1,7 e 2,1 dias para fígado, nos tratamentos T0-14, T7-21, T14-28, T21-35, T28-42, T35-49 e T42-56 respectivamente. Dessa forma, a meia-vida dos tecidos estudados, em geral, aumentou de acordo com o avanço da idade de avaliação. Dentre os tecidos estudados, a tíbia apresentou maiores valores de meia-vida, indicando lenta incorporação do carbono-13 e o fígado, os menores, sugerindo rápida incorporação. De acordo com os resultados deste estudo, pode-se concluir que a tíbia apresenta turnover e metabolismo lento indicando o sinal isotópico das dietas iniciais da criação dos frangos de corte; e o fígado, turnover e metabolismo rápido, indicado para refletir a dieta próxima da fase de avaliação. / Abstract: This study aimed to evaluate carbon-13 turnover on Pectoralis major, keel, tibia and liver of poultry at different life stages using the carbon stable isotopes technique. In this trial, 216 male chick lings (Cobb) were allocated in 36 galvanized iron cages with gutter-like feeders and nipple-like water dispensers. The trial was conduced in a totally random distribution consisting on seven treatments with distinct days for diet substitution (0, 7, 14, 21, 28, 35, 42 days old). Either Boltzmann sigmoid regression or the exponential time function was used in order to measure the carbon-13 turnover (isotopic dilution) in a specific period of time. The values of half-life was: 2.5, 2.8, 2.9, 4.9, 5.1, 5.5 and 6.0 days for muscle tissue, 2.7, 2.9, 3.1, 4.6, 5.3, 4.1 and 8.0 days for keel, 4.4, 3.6, 5.4, 5.8, 4.3, 5.2 and 6.3 days for tibia; and 1.3, 1.9, 1.4, 1.5, 1.9, 1.7 and 2.1 days for liver, on T1, T2, T3, T4, T5, T6 and T7 treatments, respectively. Generally, the half-life of the studied tissues increased along with the increase on the evaluated ages. The half-life of tibia was higher than the other tissues, indicating the slow carbon- 13 incorporation. The half-life of liver presented the smallest value indicating fast incorporation of carbon-13. According to the results of this study, it is possible to conclude that tibia has slow metabolism and it may indicate the isotopic signature of initial broiler diets, and the liver, fast metabolism tissue, is appropriated to reflect the diets fed at a closer evaluation period. / Mestre

Major and trace metal loading to mountains in the western US depends on dust sources, intensity of storms and their availability for transport during snowmelt and runoff. Previous work has been conducted on dust production, composition, and its affect on solar radiation and timing of snow melt. This study was conducted to 1) examine temporal and spatial variability in dust chemistry; 2) evaluate form and availability of major and trace elements in dust; and 3) identify potential dust sources affecting mountains in Utah and Nevada. Spring and summertime dust was collected across northern Utah over the course of three years (2013-2015). Additional dust samples were collected from eastern Nevada for comparison. All samples were analyzed for mineralogy. The spring dust samples were also leached with 1 M acetic acid, 0.8 M nitric acid, and aqua regia and analyzed for 87Sr/86Sr ratios and concentrations of 40+ trace and major elements. Nearly all dust samples were enriched in playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Mn, Zn, Cu, Pb, Se, Cd) relative to average upper continental crust. Leachate results showed that nearly 60% Ca, Sr, and Cd mass is potentially available for transport during snowmelt and that the rare earth elements could be mobilized under lower pH conditions in the soil zone. A major dust event on 17 March 2014 that was sampled across the study area showed spatially variable trace element concentrations and 87Sr/86Sr ratios, indicating that dust deposited to mountain snowpack originated from multiple upwind desert dust source areas. The NOAA HYSPLIT model was used to calculate back trajectories for this dust event and showed potential dust sources ranged from the Sevier, West and Great Salt Lake deserts in Utah and the Snake River Plain in Idaho. In contrast, multivariate statistical analysis showed that over the course of the study samples had unique geochemical signatures within each sample area. These findings suggest that spatial variability is more important than temporal variability in terms of the chemistry of dust deposition. With increasing populations and land use change in the western US, the short and long term effects of aeolian dust deposition to mountain environments need to continual monitored and constrained.

Cova des Pas de Vallgornera (CPV) is morphologically and scientifically, the most prominent karst feature of Mallorca Island (Spain). It consists of over 74 km of passages developed within two carbonate lithologies (reef front and back reef facies) of Upper Miocene age. Two distinct cave patterns are recognized, both tightly controlled by the type of facies; spongework mazes and collapse chambers are characteristic for the reef front unit, whereas linear, fracture-guided galleries develop in the back reef carbonates. CPV is abundantly decorated with a variety of speleothems. The overarching goal of this study is to provide evidence towards the cave's major speleogenetic pathways using diagnostic mineral assemblages and a set of micro- and macro-scale morphological features. In particular, this research investigates whether hypogene processes were/are the main driving force in CPV's speleogenesis and how mineral assemblages and cave morphologies help untangle the complex evolution of the cave. The mineralogy of speleothems (crusts, nodules, crystals, earthy masses) deposited in the vicinity of hypogene features in the reef front is characterized by the presence of aragonite, ankerite, huntite, clay minerals, and quartz. In the back reef limestone, however, the dominant mineral is dolomite, along with aragonite, celestine, huntite, clay minerals, and quartz. Calcite is by far the most ubiquitous mineral throughout the cave. A total of twenty-six minerals were identified throughout the cave; the highest diversity (20 species) is around or inside typical hypogene features occurring within the back reef limestone, whereas in the seaward part only 13 minerals occur. Detailed macroscopic and scanning electron micro-chemical analysis and imaging have permitted the investigation of textural relationships between the minerals associated with vents, rims, and corrosion cupolas above them. These studies along with morphological and stable isotope analyses (δ13C, δ18O, δ34S), confirm that not all minerals are connected with a hypogene stage in the cave evolution, and furthermore, none of them appears to be sulfuric acid by-products. Instead, the mineral assemblages documented in speleothems from CPV clearly support at least three speleogenetic pathways, namely seacoast mixing, ascending of warm groundwaters (basal recharge), and vadose (meteoric recharge). In summary, we have shown that cave minerals (in association with particular cave morphologies) in CPV hold the keys to understanding mineral-forming processes, conditions, and events, allowing establishing their relationship with various speleogenetic pathways.

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.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 139-147. Also available online.