http://hdl.handle.net/1974/799 Sun, 19 May 2013 12:42:03 GMT 2013-05-19T12:42:03Z http://hdl.handle.net/1974/8022 Title: Characterization of Uranium and Rare Earth Element Mobility and Attenuation Downstream of Decommissioned Tailings Impoundments at the Bicroft Mine near Bancroft, Ontario Authors: Laidlow, Allison Abstract: Attenuation of uranium (U) and rare earth elements (REEs) has been observed in stream and wetland sediments, but the geochemical and mineralogical processes involved in sequestering these elements in natural systems are not well understood. The decommissioned Bicroft Uranium Mine near Bancroft, ON uses a modified stream and wetland system to reduce the concentrations of U and other metals in tailings pond effluent to levels below the Provincial Water Quality Objectives. The Bicroft Mine was operated from 1957 to 1963, and processed low-grade (~0.17 wt% U3O8), disseminated U hosted by pegmatite dykes in amphibolite gneiss, forming 2,284,421 tonnes of tailings, deposited into two tailings impoundments. The Bicroft site has since operated as a passively attenuating stream and wetland remediation system for 55 years, demonstrating the potential longevity and viability for long-term sequestration of U and REEs through natural attenuation. To identify U and REE hosts and their stability in the natural environment, colloids, tailings, stream and wetland sediments were analyzed using various methods, including tangential flow filtration (TFF), ICP-ES/MS, scanning electron microscopy, and synchrotron techniques (bulk and µXANES, µXRF, and µXRD). The results show that Fe- and Mn-oxyhydroxides, goethite, and birnessite are the main mineral hosts for U and REEs in both the colloids and sediments. In addition, detrital grains of U- and REE-bearing minerals were found >200 m downstream in colloids and wetland sediments, showing the potential for long range transport of colloids and particulates in the stream system. Seasonal influences on the stability of trace metals in sediments were observed, and may demonstrate the limitations of passively attenuating remediation systems as a viable method for attenuation. Changes in the redox state of the stream system were observed to influence the attenuation of U and REEs, however, changes in the redox state with depth in the wetland sediments were not observed, and showed no direct influence on the attenuation of U and REEs. The results of this study will help to develop better monitoring strategies for U tailings sites and should reduce the impacts of future U mining operations. Description: Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-05-06 07:44:03.327 Mon, 06 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8022 2013-05-06T04:00:00Z http://hdl.handle.net/1974/8003 Title: IN SITU STRESS ESTIMATION METHODS AND THE INTEGRATION OF NUMERICAL MODELLING FOR STRESS RECONSTRUCTION AND FUTURE STRESS EVOLUTION Authors: Gaines, Steven Abstract: A reliable estimation of in situ stress orientation and magnitude is necessary for determining wellbore stability in the oil and gas industry, or assessing excavation stability for mining and civil engineering projects. Methods of stress estimation in deep borehole investigations are generally limited to the use of hydraulic methods or borehole imaging techniques, which identify borehole breakouts and/or borehole deformation. However, the collection of data in a thrust regime, or in horizontally laminated ground, can be difficult and lead to unreliable results. Moreover, the back analysis of stress magnitude from both hydraulic methods and borehole imaging methods are sensitive to estimates of strength and elastic properties around the borehole. This research has shown that the magnitude of the axial stress relative to the stresses normal to the borehole axis contributes to the magnitude and distribution of maximum deviatoric stress experienced around an advancing borehole. Furthermore, an analysis of the stress path incorporating the complete stress tensor shows that the maximum deviatoric stress does not always correlate with the typical solutions for induced stresses around a circular excavation. As a result of the limitations and uncertainties associated with traditional stress estimation methods, an integrated approach to determining the stress conditions at a given site using numerical models to simulate the loading history has been evaluated. A 2-dimensional finite element model of the Paleozoic sedimentary sequence of the eastern edge of the Michigan basin has shown that a systematic incorporation of the geological and stress history can approximate a given stress profile. Numerical models are also applied for estimating the magnitude of glacially induced stress change in the upper crust for the purpose of estimating long-term stress evolution. The framework and methodology used for numerical stress reconstruction and evolution can be included at the site characterization and engineering design stages for various types of projects, including deep geologic repositories, where estimates of in situ stress and future stress change are important. Description: Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-04-29 13:26:53.082 Wed, 01 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8003 2013-05-01T04:00:00Z http://hdl.handle.net/1974/7811 Title: The Role of the Tyrrell Sea Aquitard and Bioherms in the Hydrogeology of the James Bay Lowlands Under Dewatering Conditions Authors: Ali, KELLY Abstract: The Hudson-James Bay Lowlands (HJBL) are composed of fens and bogs frequently intersected by rivers and punctured by bioherms (ancient reef mounds) rising from bedrock aquifer. The peatlands exist partly due to minimal vertical losses limited by the low hydraulic conductivity (K) of the Tyrrell Sea sediments and small vertical gradients between the surface and bedrock aquifers. The recent development of an open-pit mine; DeBeers Victor Diamond Mine within the HJBL requires dewatering of the regional limestone aquifer to a depth of 200 mbgs. Two major components in assessing the potential impacts of dewatering on the hydrogeological regime and the sensitive peatland ecosystem are: the characteristics and behaviour of the Tyrrell Sea aquitard, and bioherms as potential recharge enhancing features. The Victor Tyrrell Sea (VTS) deposits are clayey silt with low LL, low PI, and no smectite clay minerals. The clay fraction consists of quartz, illite, chlinochlore, and usually calcite. The deposits are normally consolidated with Cc values of 0.08-0.155 and void ratios of 0.52-0.77. The VTS deposits are grey with pockets of black graphite and frequent shells. The K rages from 6.6x10-9 to 4.7x10-8 m/s. GEO-SLOPE™ finite element modeling software was used to investigate the sensitivity of surface drainage and consolidation behaviour in regard to the range of measured VTS parameters. The behaviours were also compared to classic clay aquitard types such as Lake Agassiz and Lake Champlain. Unit thickness, K, and the K modifier function have the greatest impact on the rate and magnitude of consolidation, and vertical drainage of the surface. The K of the underlying till is extremely important because they can be a buffer between the dewatered bedrock aquifer and the VTS. The characteristics of the sediments and the flow regime surrounding three outcropping bioherms which increase vertical drainage are investigated and a conceptual model of flow is proposed. The sediments in profile around bioherms have different levels of stratification but always contain silt and sand units. The hydraulic conditions at eight nested piezometers and the stratigraphy as defined by a series of auger hole profiles was considered to develop a conceptual model. The flow regime presented is of radial flow towards the bioherms enhanced by high K sediments between the peat and bedrock becoming vertical flow when the high K sediments contact vertical channels in the rock. Description: Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-02-06 14:47:13.582 Thu, 07 Feb 2013 05:00:00 GMT http://hdl.handle.net/1974/7811 2013-02-07T05:00:00Z http://hdl.handle.net/1974/7628 Title: GEOCHEMICAL AND MINERALOGICAL EVOLUTION OF THE MCARTHUR RIVER ZONE 4 UNCONFORMITY-RELATED URANIUM ORE BODY AND APPLICATION OF IRON OXIDATION STATE IN CLAY ALTERATION AS INDICATOR OF URANIUM MINERALIZATION Authors: Ng, RONALD Abstract: 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. Description: Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-11-01 14:08:33.51 Mon, 05 Nov 2012 05:00:00 GMT http://hdl.handle.net/1974/7628 2012-11-05T05:00:00Z