The eastern margin of the Proterozoic Athabasca Basin in northern Saskatchewan is host to several of the highest-grade unconformity-related (U/C-related) uranium deposits in the world. Many researchers agree that uranium deposition occurred due to oxidized basinal brines transporting uranium mixing with reducing fluids or interacting with reduced rock causing uranium to precipitate, although the source of the uranium is still an unresolved and highly debated subject. Boron isotopic signatures, preserved in refractory minerals such as tourmaline, can aid in determining the source of fluids and P-T conditions during crystallization whereas lithium isotopic fractionation is indicative of weathering, hydrothermal alteration, and/or igneous and metamorphic processes. For this study a suite of fresh to strongly altered basement samples were selected from multiple sites below the eastern Athabasca Basin to measure the bulk delta7Li, delta11B and Pb-Pb isotopic signatures. Kinetic modelling of the Li and B isotopic systems suggest that both systems are slightly conservative of their original fluid reservoir, and by calculating the Damkohler numbers (ND) it is predicted that delta11B will be more indicative of the fluid source whereas lithium isotopes will equilibrate over shorter distance. However, both isotopic systems will fractionate with large concentration changes. Significant variations were observed for both delta7Li and delta11B, delta7Li values ranged from 0 to 14 ‰, the range in delta7Li was interpreted to be representative of both partial melting of metasediments to form granitic pegmatites and hydrothermal fluids. In comparison the range for delta11B was much larger from -16 to +17‰, within the dataset there appeared to be regional isotopic differences but unfortunately this dataset was too small to determine regional isotopic patterns. For each region the delta11B for the pegmatites was often heavier than the metasedimentary samples suggesting a metasedimentary source for the granitic pegmatites. Elevated U concentrations and decreasing 207Pb/206Pb ratios in both altered and unaltered samples suggest radiogenic Pb and U are present both in the basement and in fluids transporting U through the basement. Partial digestion 207Pb/206Pb ratios range from the common 207Pb/206Pb ratios of 0.7 to radiogenic 207Pb/206Pb ratios of 0.1. The radiogenic 207Pb/206Pb are indicative of either resetting of residual material during fluid migration or radiogenic fluids sources interacting with the rocks of this study.

The Coats-Hines site (40WM31) is a potential pre-Clovis site located in Franklin, Tennessee. The site rests, geographically, at the convergence of the Central Basin and Western Highland Rim. The site was discovered during the construction of a nearby golf course when a salvage team uncovered a mature female mastodon.. The site was later excavated in 1994-1995, during which time two additional mastodons were uncovered, in direct association with lithic artifacts. Preliminary radiocarbon dates reveal the site was deposited during the late Pleistocene epoch at roughly 12,000^(14)C yr BP. During the summer of 2012, the site was excavated with the goal of determining the depositional setting of the site and geographic region, as well as establishing the antiquity of the archaeological remains. The site geology was determined through field interpretation and texturing, micromorphological analysis, laboratory particle size analysis, and radiocarbon dating. Sedimentation at the site is a combination of cherty colluvium from upslope as well as alluvium. Four chronostratigraphic sequences of sedimentation were determined to have occurred during the last glacial, the Pleistocene-Holocene transition, the Holocene, and modern time periods. The volume, distribution, and composition of the nine defined stratigraphic units are dependent on the fluctuations occurring in the climate during these time periods. The climate changes and rates of deposition occurring at Coats-Hines were correlated to similar sites in the region. The Coats-Hines site was surveyed along the wet-weather drainage that bounds the site during in the spring of 2013. A channel unconformity was discovered, likely dating to the Pleistocene-Holocene transition and providing context to the 1994/1995 excavation.

Two Paleoproterozoic basins, the western Thelon Basin, and the Otish Basin, Canada, were investigated using basin analysis to evaluate critical factors for the formation of unconformity-related uranium deposits. The results serve to guide ongoing exploration at two under-studied uranium prospects in each basin, and help predict whether or not these basins have the potential to host high-grade uranium deposits in other locations. Sequence stratigraphy, in combination with mineral paragenesis indicates that unmetamorphosed basinal sandstones overlying the Boomerang Lake prospect, western Thelon Basin, were compacted and occluded by kaolinite and muscovite during diagenesis, and became diagenetic aquicludes that were unable to effectively conduct uranium-bearing basinal brines. Based on the high δ18O values of basinal and basement-influenced fluids, and the preservation of pre-Thelon-Basin 40Ar/39Ar dates of poorly-crystalline phyllosilicates in the basement rocks, hydrothermal alteration and uranium mineralization must have occurred at low water/rock ratios. This produced uneconomic amounts of U-bearing phosphate that was misidentified as uraninite in a previous report. A significant uranium deposit is unprobable based on the lack of unsupported radiogenic Pb near the prospect. However, intersections of thick, stratigraphically-higher diagenetic aquifers, which are marked by abundant dickite, and structurally-reactivated basement rocks on a different exploration trend remain the most prospective locations for a uranium deposit in the area. At the Camie River prospect, Otish Basin, diagenesis of basinal sediments in thick diagenetic aquifers was associated with fluids that were isotopically similar to seawater-derived basinal brines. The 1721 ±20 Ma Pb/Pb date obtained for Camie River uraninite coincides with intrusions of the Otish Gabbro, which triggered basinal fluid flow in diagenetic aquifers and uranium mineralization throughout the basin. The effects of late hydrothermal, metamorphic, and meteoric fluid events are restricted to fractures and faults. These zones also preferentially host radiogenic Pb and pathfinder elements that dispersed from the prospect, which can be utilized to vector towards additional deposits. The unconformity-type deposit model can be extended to basins as old as 2.0 Ga, as the Otish Basin demonstrates that atmospheric oxygen contents were high enough at this time to allow the evolution of U-leaching oxidizing basinal brines. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2011-01-29 15:45:53.651

During the Paleoproterozoic Era (ca. 2.5 Ga to 1.6 Ga), Earth underwent dramatic changes to its tectonic and atmospheric parameters. These changes included: the formation and breakup of the supercontinent Nuna (Columbia) and the gradual rise in atmospheric oxygen levels. The gradual rise in atmospheric oxygen, referred to as the Great Oxidation Event (GOE), altered the behaviour of silicate mineral weathering, and permitted the formation of new types of economic uranium deposits. Beaverlodge Lake, Northwest Territories (NT), allows for the study of a weathering profile and uranium mineralization post GOE. At Beaverlodge Lake, NT, a regolith is preserved in a rhyodacitic porphyry of the ca. 1.93 Ga Hottah plutonic complex, which is unconformably overlain by the ca. 1.9 Ga quartz arenite of the Conjuror Bay Formation. Coincident with the unconformity is a past-producing uranium deposit (called the Tatie U deposit), which was mined out in the 1930s. Other uranium showings have been discovered at Beaverlodge Lake including the Bee showing. The initial purpose of this project was to examine the regolith through field, petrography, electron microprobe analysis (EMPA), whole-rock geochemistry, and mass balance calculations. The weathering profile shows an increase in Al2O3, Fe2O3T, K2O, P2O5, Ba, and Rb, a loss in SiO2, Na2O, MgO, and Sr, and constant and low abundance of CaO. Titanium remains constant in the weathering profile. Rare earth element (REE) analysis reveals remobilization of light REE (LREE) on a micrometer scale, but no cerium anomaly is preserved in the weathering profile. The weathering profile displays characteristics similar to other post GOE paleoweathering profiles developed on felsic parental material. The timing of uranium mineralization at Tatie and Bee was constrained by in-situ U-Pb uraninite dating by Secondary Ion Mass Spectrometer (SIMS), which yielded two variably discordant ages of 1370.2 ± 7.9 Ma and 407 ± 21 Ma. In addition, REE contents of uraninite were determined by in-situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results revealed two types of uraninite mineralization are preserved at Beaverlodge Lake and they consist of synmetamorphic at Bee and basement-hosted unconformity-type at Tatie similar to those in the Athabasca Basin. The ca. 1370 Ma uraninite (Tatie) is characterized by an asymmetric bell-shaped REE pattern centered on Tb to Er where LREEs are depleted compared to heavy REEs (HREE). The ca. 407 Ma uraninite at Bee has low La concentrations and a flat to slightly negative REE pattern. The Mesoproterozoic age is similar to a Pb loss age of ca. 1400 Ma found in the Athabasca Basin. The younger Devonian age may be related to meteoric fluids cycling and uranium remobilization during the Phanerozoic.

The sandstone-hosted McArthur River Zone 4 U ore body and alteration system, located in the Athabasca Basin, are the focus of a detailed mineralogical and geochemical study aimed at reconstructing its evolution. The oxidation state of Fe in clay alteration from Zone 4 is measured using 57Fe Mössbauer spectroscopy and compared with other mineralized and barren sandstone-hosted alteration systems in the Athabasca Basin. The aim is to ascertain the role of Fe in forming U deposits and determine whether Fe oxidation state in alteration minerals can indicate proximity to mineralization. At Zone 4, early diagenetic kaolin is overprinted by zones of dravite, illite, chlorite, and late kaolinite forming around the P2 fault. Uranium mineralization occurred at ca. 1600 Ma and was triggered by mixing between oxidizing U-bearing basinal fluids and reducing basement-modified basinal fluids, the latter forming when basinal fluids interacted with basement lithologies. Early pre-ore silicification in the lower 200 metres of the Manitou Falls Formation above the ore body created favourable conditions for mineralization by focusing basinal fluids into the reduction site and enhancing ore preservation. However, it obstructed the post-ore migration of radiogenic Pb and U pathfinder elements from the deposit and limited the extent of hydrothermal sudoite alteration in the overlying strata. Sandstone-hosted alteration systems in the Athabasca Basin are commonly surrounded by an outer illite and an inner chlorite zone. Illites have high Fe3+/ƩFe ratios characteristic of formation from oxidizing basinal fluids, whereas, chlorites have lower and more varied Fe3+/ƩFe ratios, reflecting their origin from reducing, Fe2+-bearing basement-derived fluids having undergone variable mixing with oxidizing basinal fluids. Chlorites in mineralized systems where fluid-mixing occurred, such as at McArthur River Zone 4 and Maurice Bay, record higher Fe3+/ƩFe ratios than barren systems where fluid-mixing did not, such as at Wheeler River Zone K and Spring Point. The scarcity of U-bearing basinal fluids available for mixing with Fe2+-bearing basement fluids is a critical geochemical factor precluding mineralization in barren sandstone-hosted systems. The Fe3+/ƩFe ratio of chlorites has potential applications for discriminating barren and mineralized systems and as spatial vectors to ore when coupled with Pb isotope ratios. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-11-01 14:08:33.51

In the Death Valley and Mojave Desert regions of southeastern California, the contact separating the lower and middle members of the Wood Canyon Formation (WCF) is currently interpreted as a regional scale unconformity coincident with the base of the Sauk Sequence. Regional mapping of this surface, however, reveals a nonconformable contact with underlying crystalline basement in cratonic settings, and a relatively conformable contact atop a northwest thickening wedge of miogeoclinal strata that is capped by the lower member of the WCF. Consistent with an unconformity, the progressive loss of three carbonate units within the lower member of the WCF has been attributed to incision by the base of the middle member WCF. However, fossil evidence and correlation based on carbon isotope compositions of each lower member WCF dolostone units rejects top-down erosion to describe their loss and overall cratonward thinning. Results from multiple detailed, measured, stratigraphic sections of a conglomerate found at the base or low in the middle member WCF also do not support a top-down erosion model because the conglomerate has variable stratigraphic position and absence in some locations. Middle member WCF conglomerate clasts also reveal variation in composition and grain size across the regions. Sequence stratigraphic architecture indicates that filling of available accommodation space and short period normal regression, as opposed to a forced regression, are the causal mechanisms for formation of the basal middle member WCF unconformity, and that the base of the Sauk Sequence rests lower in the stratigraphic section.

The continental margin off Nova Scotia (the Scotian margin) forms the northern edge of the North American Basin. The Cenozoic stratigraphy and geological history of the outer margin is not well known. This study examines aspects of the Upper Cretaceous-Cenozoic geological history of the outer Scotian margin addressing the following objectives: 1) determine the geological history of a large deep-water depocenter, 2) investigate processes that led to deep-water unconformity formation in the study area, 3) determine the role of deep-ocean circulation in margin evolution, 4) examine the effects of morphological heritage on subsequent depositional patterns. High quality 2-D and 3-D seismic reflection data along with lithostratigraphic and biostratigraphic data from hydrocarbon exploration wells provide the basis for this investigation. The seismic stratigraphy of a large deep-water depocenter along the western Scotian margin was broadly divided into four units. Unit 1 (Upper Cretaceous-Upper Eocene) is attributed to repeated, widespread erosion events interspersed with periods of hemipelagic and pelagic, carbonate-rich sedimentation. Unit 2 (Lower Oligocene-Middle Miocene) consists of a variety of seismic facies overprinted by dense, small-offset faults. Unit 3 (Middle Miocene-Upper Pliocene) is dominated by sediment drift deposition. Unit 4 (Upper Pliocene-present) is characterized by channel development and gravity flow deposition. The processes that led to regional seismic stratigraphic horizons were complex. Both large mass-wasting events and along-slope bottom currents contributed to the formation of unconformities in the study area. Most of the succession preserved in the depocenter belongs to seismic units 2 and 3. These deposits are mainly confined to the area seaward of the Abenaki carbonate bank and landward of shallow salt structures below the slope. Locally, however, modification of the slope profile through mass-wasting and bottom current processes greatly influenced subsequent depositional patterns. The Cenozoic geological evolution of the study area was strongly affected by northeast-to-southwest flowing bottom currents. The earliest indication of bottom current activity was in the Eocene. Upper Miocene and Pliocene sediment drifts represent >50% of the preserved stratigraphic section in the thickest part of the depocenter. It is clear that along-slope sedimentary processes were far more important in shaping the margin than previously understood.

A study of the Millennium and Eagle Point basement-hosted deposits was conducted to obtain a comprehensive understanding of the alteration in these two atypical uraniferous systems and to apply these findings in formulating effective exploration strategies. In addition, an investigation of the Wheeler River “apparently barren” sandstone-hosted alteration system was conducted to provide insights into the critical events needed in order to form sandstone-hosted unconformity-related deposits. At Millennium, the atypical alteration halo, wherein the inner chlorite halo is much smaller than other basement-hosted deposits, is the result of pervasive muscovite alteration of the basement rocks by Na-K-Fe basinal brines during the pre-ore stage at ca. 250°C. As alteration of the basement rocks progressed, the basinal brines acquired Ca, Fe and Mg while creating up to 20% voids in the basement rocks. Prior to the mineralizing event, the chemically modified basinal fluids formed a minor Fe-rich chamoisite halo that demarcates a redox front during the ca. 1590 Ma syn-ore stage, where uranium ore was precipitated. At Eagle Point, the atypical alteration halo, wherein dolomite and calcite alteration is more significant than other basement-hosted deposits, is the result of more intense pre-Athabasca Basin alteration. The Eagle Point deposit is also distinct by significant late remobilization of primary uraninite into secondary structures that occurred at ca. 535 Ma. At the Wheeler River “apparently barren” alteration system, the critical factor for the lack of uranium mineralization in the sandstone is the temporal relationship between the different fluids with the uranium-bearing oxidized basinal fluids present prior to the reduced chemically modified basinal fluids and reduced basement fluids. However, the possibility of a small basement-hosted uranium deposit at Wheeler River cannot be excluded because the sudoite-producing basement fluids may represent basinal brines that reacted with basement lithologies to become reducing and Mg-rich, and therefore may have precipitated uraninite during this process. The results of this study support the genetic model in which basinal fluids were likely the source of uranium deposits and that the basement fluids were unlikely significant sources of uranium in sandstone-hosted deposits. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2009-09-30 14:49:03.688

This study aimed to contribute to baseline knowledge of permafrost geochemistry within the uppermost 3-4 m of permafrost at 8 sites on the Peel Plateau and east of the Mackenzie Delta, NWT (67-68oN). The following variables were measured: gravimetric water content (GWC), pore water conductivity (PWC), leachate conductivity (LC), dissolved ions by ICP-AES (i.e. Ca, SO4, Mg, Fe, K, Na, Mn, Cl), organic carbon content (calculated by linear regression from organic matter content), as well as inorganic carbon content (obtained from loss on ignition analysis). PWC was positively correlated to GWC and values were generally at least 5 times less than LC values, likely underestimating total dissolved solutes using the former method. LC increased with depth to reach maximum values below the paleo thaw unconformity (>10 mS/cm). Carbon content typically remained low throughout the cores with the exception of samples associated to the shallow-rooted vegetation cover at the ground surface. Results showed that the active layer, relict active layer and the permafrost below the thaw unconformity can be divided into three statistically significant layers. PCA results indicated some spatial patterns with increasing LC values at greater depth, suggesting that layer geochemical profiles reflect varying degrees of soil chemical weathering processes since the early Holocene.

Les circulations de fluides aux interfaces entres les socles cristallins et leur couvertures sédimentaires sont des événements majeurs de transferts élémentaires dans la croûte. Dans de nombreux contextes, des fluides de bassins peuvent pénétrer dans les socles de faible perméabilité, interagir avec eux, y lessiver des métaux, et donner lieu à des concentrations métalliques, notamment en Pb, Zn, Cu, Ag et U. Les gisements d’uranium de type discordance du bassin d’âge protérozoïque de l’Athabasca (Canada), sont des témoins essentiels de ce type de circulations de fluides, et sont des objets modèles pour comprendre les mécanismes et les conséquences de tels événements. Les inclusions fluides permettent d’échantillonner et d’analyser directement les paléofluides. Malgré les difficultés d’analyse, ces objets de taille micrométriques apportent des informations importantes sur les propriétés des fluides. Les techniques d’analyse disponibles (microthermométrie, LA-ICP-MS, écrasement-lessivage, écrasement sous vide) permettent de reconstituer la température, la pression, la composition chimique détaillée des fluides, dont les teneurs en métaux, ainsi que la composition isotopique de l’hydrogène de l’eau, du chlore et du carbone du CO2 dissous. De plus, l’analyse de la composition isotopique de l’oxygène et du carbone des minéraux dans lesquels sont piégées les inclusions fluides apporte des informations complémentaires sur la température des fluides et les interactions fluides-roches. Cette approche a été utilisée sur six gisements d’uranium du Bassin de l’Athabasca, et a permis d’apporter les résultats suivants, potentiellement généralisables à l’ensemble du bassin. (1) Deux saumures, une calcique et une sodique ont circulé et se sont mélangées à la base du bassin et dans le socle au cours de la formation des gisements à environ 150 ± 30°C. (2) Ces deux saumures ont transporté de l’uranium, dont les concentrations exceptionnelles et très hétérogènes (entre 0.2 et 600 ppm) indiquent qu’il a été lessivé dans le socle. (3) Ces saumures ont une origine commune et se sont formées essentiellement par évaporation en surface de l’eau de mer, et mélange avec des fluides issus de la dissolution de minéraux évaporitiques. (4) La saumure calcique s’est formée par interaction entre la saumure sodique et les roches du socle. (5) Les interactions des saumures avec les minéraux et le graphite du socle, la radiolyse de l’eau, et la synthèse de bitumes ont contrôlé la composition isotopique en oxygène, hydrogène et carbone de ces saumures. / Fluid circulations between crystalline basements and their sedimentary covers are major events for element transfer in the crust. In numerous settings, basinal fluids penetrate the low-permeability basement, interact with basement lithologies, leach metals, leading to metal concentrations, notably Pb, Zn, Cu, Ag and U. Unconformity-related uranium deposits from the Proterozoic Athabasca Basin (Canada) are crucial witnesses and useful tools for the understanding of mechanisms and consequences of such fluid events. Fluid inclusions allow us to directly sample and analyze paleofluids. Despite analytical difficulties, these micrometer size objects provide key information on fluid properties. Available analytical techniques (microthermometry, LA-ICP-MS, crush-leach, in-vacuo crushing) provide reconstruction of temperature, pressure, detailed fluid chemistry, including metal concentrations, as well as isotopic composition of water hydrogen, chlorine and of dissolved CO2 carbon. In addition, analysis of isotopic composition of oxygen and carbon from minerals in which fluid inclusions are trapped provide supplementary information on fluid temperatures and fluid-rock interactions. This approach was used on six uranium deposits from the Athabasca Basin and provided the following results, which can be potentially generalized to the entire basin. (1) Two brines, a calcium-rich brine and a sodium-rich brine have circulated and mixed at the base of the basin and in the basement at the time of formation of uranium deposits, at temperature close to 150 ± 30°C. (2) Both brines have transported uranium, whose exceptional and highly heterogeneous concentrations (0.2 to 600 ppm) indicate that it was leached in the basement. (3) Both brines share a common origin and were formed mainly by surface evaporation of seawater and mixing with fluids originating from dissolution of evaporitic minerals. (4) The calcium-rich brine was formed by interaction between the sodium-rich brine and basement lithologies. (5) Interaction with basement minerals and graphite, water radiolysis, and bitumen synthesis were the main controls on the oxygen, hydrogen and carbon isotopic composition of brines.