The Thelon basin, Nunavut, is similar to the uranium-producing Athabasca Basin, Saskatchewan; however, the uranium deposits associated with the Thelon Basin are poorly understood. The objective of this research is to develop a genetic model for the Bong uranium deposit, located in the Northeast Thelon region on the Kiggavik project of AREVA Resources Canada Inc. The Bong deposit formed in four stages. The first stage involved silicification of the host rocks. Stage 2 is characterized by pervasive argillization of the host rock and the formation of Stage A uraninite in veins and coating graphite (~1120 Ma). This stage is characterized by ~225°C fluids with calculated δ18O and δD values of -7.9‰ and -100.9‰, respectively. During Stage 3, organic matter formed, along fractures in permeable clay-rich alteration zones. At ~1040 Ma, an oxidizing fluid event (Stage 4) reconcentrated uraninite into redox fronts (Stage B) and altered Stage A uraninite to uranophane.

The Thelon basin, Nunavut, is similar to the uranium-producing Athabasca Basin, Saskatchewan; however, the uranium deposits associated with the Thelon Basin are poorly understood. The objective of this research is to develop a genetic model for the Bong uranium deposit, located in the Northeast Thelon region on the Kiggavik project of AREVA Resources Canada Inc. The Bong deposit formed in four stages. The first stage involved silicification of the host rocks. Stage 2 is characterized by pervasive argillization of the host rock and the formation of Stage A uraninite in veins and coating graphite (~1120 Ma). This stage is characterized by ~225°C fluids with calculated δ18O and δD values of -7.9‰ and -100.9‰, respectively. During Stage 3, organic matter formed, along fractures in permeable clay-rich alteration zones. At ~1040 Ma, an oxidizing fluid event (Stage 4) reconcentrated uraninite into redox fronts (Stage B) and altered Stage A uraninite to uranophane.

This thesis presents a 40Ar/39Ar geochronological analyses of biotite from thin ductile shear zones in Paleoproterozoic granulite-facies gneisses from the Ellesmere-Devon crystalline terrane, Nunavut, Canada. The gneisses are part of the Paleoproterozoic Thelon tectonic zone. U-Pb dates of zircon show that the gneisses have magmatic protolith ages ranging from 2007–1958 Ma. The quartzofeldspathic gneisses in southeast Ellesmere Island display centimeter-scale E- to NE-striking sinistral and dextral mylonite zones offsetting pegmatitic dikes that are the last stage of ductile deformation of the basement rocks. Samples were taken from nearshore outcrops at Hayes Fiord, Pim Island, NE of the Leffert Glacier and NW of Cape Isabella. Biotite clusters replace orthopyroxene as the result of post-granulite facies metamorphism in the gneisses. Biotite in mylonitic and ultramylonitic fabrics is found as flattened clusters and also as individual crystals defining shear bands related to mylonitization. Eight samples were dated, including biotite from five mylonites, one deformed pegmatite, one tonalite and muscovite from a pegmatite. Major element X-ray maps demonstrate that the biotite is chemically homogenous. Backscattered electron images and electron dispersive spectroscopy via scanning electron microscopy confirm that biotite lacks intercrystalline layering with other K phases. Step-heating analysis of mica at the University of Vermont yielded Paleoproterozoic 40Ar/39Ar ages. The apparent age spectra form plateau ages in all but one mylonite sample. Biotite from a protomylonite was 2051 ± 26 Ma, older than the protolith ages obtained from U-Pb zircon geochronology, and most likely indicates excess Ar. Pegmatitic muscovite was 1977 ± 35 Ma. Biotite dates range from 1874 ± 13 Ma to 1838 ± 14 Ma for the five mylonites without excess Ar. Biotite dated from ductile shear zones signals the latest deformation in the basement, which was active as early as 1887 Ma.

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

Thesis (Ph.D)--Harvard University, 1952. / Typescripts, signed; typescripts; typescripts (carbon copies). Gift of Elmer Harp.

<p> The Thelon Tectonic Zone is a major structural, metamorphic and lithological feature of the Precambrian Shield in the Northwest Territories. Situated within this Zone is a 30 square kilometre plutonic body. Rubidium- Strontium whole rock geochronology yields an age range of 1650 - 2200 Ma for the emplacement of this pluton. Field and petrographic evidence indicates that the pluton has suffered post-emplacement deformation, representative of a late Proterozoic metamorphic event. Major and trace element geochemistry suggests that this high Ca, ferrogranodiorite-tonalite intrusive body is associated with a subduction-related, continental margin tectonic environment. </p> / Thesis / Bachelor of Science (BSc)

Ce travail présente une étude multi-échelle des relations entre altération et minéralisation en uranium le long de la bordure Sud Est du bassin Méso-Protérozoïque du Thelon, au Nunavut, Canada. Les altérations associées aux minéralisations sont développées dans une série volcano-sédimentaire Archéenne appartenant à la ceinture de roche verte du Woodburn Lake Group (WLG). Elles s'expriment majoritairement par un assemblage à illite (polytypes 1Mcis & 1Mtrans) ± sudoite ± hématite et phosphates sulfates d'aluminium hydratés (APS). De plus des composés carbonés, cogénétiques des minéralisations, ont été identifiés comme des produits des réactions hydrothermales. La signature de l'altération, fortement guidées par les structures Est-Ouest du corridor de Kiggavik-Andrew Lake, apparaît alors très similaire à celle rencontrée dans les roches de socles des parties profondes des autres gisements d'uranium de type discordance du bassin d'Athabasca (Canada) ou de la Kombolgie (Australie). L'étude des marqueurs minéralogiques tels que les APS ont permis de mettre en évidence les transferts élémentaires au cours des processus métallogéniques et de distinguer les caractéristiques pétrographique et chimiques des processus diagénétiques et hydrothermaux. Enfin la compréhension fine de l'expression de marqueurs cristallographiques issus de l'irradiation naturelle des minéraux argileux donne de nouvelles pistes pour le traçage et la compréhension des circulations des radios-éléments à l'échelle géologique. / This work presents a multi-scale study of the relationships between alteration and uranium mineralization along the South Eastern margin of the Meso-Proterozoic Thelon Basin, Nunavut, Canada. The ore associated alterations are hosted in an Archean volcano-sedimentary sequence belonging to the Woodburn Lake Group (WLG). Their main expression is a mineral assemblage composed of dominant illite (1Mcis & 1Mtrans polytypes) together with sudoite ± hematite and aluminum phosphate sulfate minerals. Moreover carbonaceous materials cogenetic with the uranium mineralization have been identified as potential indicators of the hydrothermal conditions. At a regional scale, alteration is strongly controlled via East-West faults forming the main frame of the Kiggavik-Andrew Lake structural trend. Then from the regional to the mineral scale, alterations signatures at Kiggavik are similar to the ones described in deep basement rocks of unconformity type uranium deposits in both Athabasca (Canada) and Kombolgie (Australia) Paleoproterozoic basins. In addition mineralogical markers studies (APS minerals) lead to the distinction between hydrothermal and diagenetic processes as well as elemental transfers during fluid rock interaction. Finally, detailed studies on radiation induced defects on illite revealed new ways to tracing and better understanding the radio elements mobility in such deep seated natural systems.

<p>The northeast Thelon Basin, Nunavut, is a rapidly developing albeit poorly studied, frontier exploration domain for unconformity-associated uranium deposits. Critical criteria for unconformity –associated uranium deposit models are knowledge of the basement geology, fault history and depth to unconformity surface. This thesis sets forth to derive working geological and geophysical models for the northeast Thelon Basin through the implementation of integrated geophysical techniques.</p> <p>A physical rock property database is compiled defining average density and susceptibility values for key map units for integration into subsequent modelling iterations. Forward and inverse potential field modelling using these petrophysical with geological controls define the structure and geometry of the Shultz Lake intrusive complex and northeast Amer Belt, both of which are present below the Thelon sedimentary cover. Implementation of a new source edge detection technique estimates fault development and location within the basin. This provides a quantitative analysis of fault timing, identifying potentially reactivated faults which have an increased likelihood to serve as conduits to transport uranium-rich fluids and focus deposition. Corroborating the geophysical signatures on the aeromagnetic map with petrophysical properties and outcrop observations, a predictive geological map is developed for area beneath the sedimentary cover sequences. Inversion and interpretation of several discrete aeromagnetic anomalies provides local source depth estimates. Knowledge of fault locations is employed to delineate fault block boundaries. Interpreted geological model profiles include abrupt changes in sediment thickness with faults while abiding with the integrated source depth estimates. Integrating the results from a number of profiles provides a pseudo-3D rendition of the unconformity surface and its relationship to known faults. The geological-geophysical models which are presented herein incorporate all currently available data while providing a framework for the inclusion of future information as the knowledge gap for this remote region diminishes.</p> / Doctor of Science (PhD)

<p>The Artillery Lake area is diagonally bisected by the north-northeasterly trending Thelon Front. The best single surface feature to represent the Thelon Front is the "straight zone" which is a zone of porphyroclastic metasediments that also contains the study area. Kinematic indicators observed in the study area include extensional shear surfaces, C&S fabric, mica "fish", asymmetrical porphyroclast tails, asymmetrical folds, microfaulted porphyroclasts and secondary quartz subgrain foliations. Kinematic analysis of these features has shown that right lateral simple shear displacements and "east-side-up" vertical shear displacements have been accommodated within the rocks of the study area. The displacement senses determined by kinematic analysis are consistent with the regional data indicating progressively deeper exposures of structural levels to the east which suggests vertical motions localized at the domain boundaries. The stretching lineation present in the area is a combination of passive and direct extensions due to sub-vertical motions in the shear zone. A transition from early-ductile to late-brittle feldspar deformation textures indicates that metamorphic conditions during initial deformation were at epidoteamphibolite facies and relaxed during the later stages of deformation to greenschist facies. </p> / Thesis / Bachelor of Science (BSc)