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We report on recent geoscience data collected by the Geological Survey of Canada in collaboration with Northwest Territories Geoscience Office and Carleton University. Fifty sediment-water interface samples from 19 lakes were collected between July and August 2009 along a 90 km east-west transect and analyzed for grain size, organic matter, nutrients, and metals. The work was undertaken to establish a dataset to contribute to the determination of natural variability of arsenic in freshwater sediments in the Yellowknife area, Northwest Territories. Geochemistry results of lake sediments are compared to previous work, bedrock geochemistry where available, and the Canadian Council of Ministers of the Environment Interim Sediment Quality Guidelines and Probable Effects Levels for the Protection of Aquatic Life. Concentrations of arsenic in bulk lake sediment samples are elevated above Interim Sediment Quality Quidelines and Probable Effects Levels in lakes located west of the city of Yellowknife. These lakes occur on granitoid bedrock, which contain low arsenic relative to other bedrock types in the study region. The spatial pattern of arsenic in lake sediments is consistent with aerial dispersion of emitted particulates from mine smelting point sources and transportation by prevailing winds west of the city of Yellowknife.

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The Hudson Bay Basin is the largest intracratonic basin in North America but also the least known from a geological point of view and the only one without hydrocarbon production and reserves. The Hudson Bay Basin, in north-central Canada, is bounded by smaller satellite basins, Moose River Basin to the south and Foxe and Hudson Strait basins to the north. It was explored for hydrocarbons from the late 1960's to the mid 1980's. However, after the drilling of five offshore wells, the industry stopped exploration programs as the basin was considered to be thermally immature with a too thin succession and problematic source rock distribution. As part of its new Geomapping for Energy and Minerals program, the Geological Survey of Canada included the Hudson Bay Basin in its research portfolio with the goal to generate a modern understanding of the geological framework of the basin and a precise knowledge of its hydrocarbon systems. The Hudson-Foxe basins GEM-1 project benefited from limited but significant research activities before its official launch in 2008. The evaluation of recent and vintage geoscientific data led to the definition of the most pertinent research activities and the development of collaborative networks with provincial, territorial and academia stakeholders. The first phase of the research led to the proposal of modern stratigraphic frameworks at the local (provincial, territorial) and regional (offshore) scales and extensive geochemistry works on hydrocarbon source rocks and their burial and thermal histories. Satellite data were acquired over the entire offshore domain of the Hudson Bay and Foxe basins in the search for evidence for active hydrocarbon systems. After the completion of Phase 1 (2008-2013), a new round of research activities were defined as part of the GEM-2 program (2013-2020). For the new Hudson Bay - Ungava project, research activities were defined aiming to understand local and/or regional factors responsible for burial and exhumation histories as they pertain to regional or local hydrocarbon prospectivity. The research led to a basin-scale stratigraphic framework coupled with detailed analyses of hydrocarbon generation and appraisal of the best potential reservoir unit. GEM supported research for the intracratonic Hudson Bay, Foxe and Moose River basins has resulted, in early 2019, in the publication of 14 peer-reviewed papers, 43 Open File reports (GSC, CNGO, GC, MGS and OGS), 13 GSC paleontological reports, 11 B.Sc. theses and 1 M.Sc. thesis. The main conclusion of the 11 years of research suggests that the Hudson Bay Basin has an oil potential likely significant compared to the belief at the start of the research and integration of the multiple data set allows to propose Paleozoic-Cenozoic filled half grabens as the potential most significant hydrocarbon play of the basin.

Ecological and human health risk assessments at active and abandoned metal mines require accurate geochemical data for earth materials, including soils, sediments, dusts, and mine wastes. Reliable data on metal(loid) concentrations are also important for establishing geochemical baselines and to support environmental monitoring activities. However, the reported concentration for an element in a given sample can be affected by many factors, including mineralogy, grain size, laboratory digestion conditions (reagents, temperature, time), and the instrument(s) used for elemental analysis. In particular, aggressive multi-acid digestion methods used to provide 'near-total' data for some metals of environmental interest (e.g. chromium (Cr), uranium (U)) may result in the loss of other elements (e.g. antimony (Sb), arsenic (As), sulfur (S)) through volatilization prior to analysis. When comparing data from different studies or sampling periods, it is crucial to ensure that the analytical protocols used are consistent and that changes in element concentrations over time are not simply due to variations in sample processing or laboratory procedures. The purpose of this study is to compare common digestion protocols used in the analysis of geological materials and provide recommendations on the most appropriate techniques for use in environmental risk assessments. We analyzed samples of lake sediments, stream sediments, soils, and mine tailings collected at metal mine sites across Canada. These samples were digested using two of the most commonly employed procedures in exploration and environmental geochemistry: a modified aqua regia digestion and a 4-acid digestion. All solutions were analyzed using ICP-ES/MS, and certified reference materials (CRMs) and duplicate samples were used to monitor analytical accuracy and precision. The concentration of elements (e.g. Cr) hosted in relatively insoluble mineral phases are consistently higher following 4-acid digestions as compared to digestions using aqua regia, but generally lower than total values measured using direct methods of analysis (e.g. Instrumental Neutron Activation Analysis). In contrast, the concentrations of As are often higher in samples following aqua regia versus 4-acid digestions and generally in good agreement with total values in CRMs. The behaviour of other elements (e.g. Sb, copper (Cu), lead (Pb), S, zinc (Zn)) was more variable and for many samples, the results following 4-acid and aqua regia digestions were statistically indistinguishable. Variations in the mineralogy of different samples play a key role in determining the fraction of different metal(loid)s released by these digestion techniques. This poster highlights some of the advantages and disadvantages of using each of these digestion protocols for risk assessment and environmental monitoring purposes, and provides recommendations for using geochemical data to help guide environmental decision-making at both active and abandoned metal mines.