Geochemical baselines and metal(loid) mobility in a changing northern climate, Courageous-Mackay Lake Greenstone Belt, Slave Geological Province, NWT

Geochemical baselines provide guidance for mineral exploration and facilitate the development of remediation objectives. Presently, national guidelines based on Canada-wide average metal(loid) concentrations in environmental media are used as reference. Metal(loid) concentrations reflect local variations in the concentration of elements in the environment and are influenced by many variables, including bedrock composition, degree of weathering, and biological processes. In northern regions, accelerated climate change has been shown to impact the mobility of some metal(loid)s and influence lacustrine geochemistry. The influence of climate change on the mobility of arsenic, is not well established. As arsenic is both a pathfinder element for mineral exploration as well as a mobile and potentially harmful by-product of mining activities, this study aims to determine the anticipated changes to arsenic mobility in sub-arctic mineralized regions. This study will examine the speciation and mobility of arsenic in lakes located near a former gold mine in the Slave Geological Province (SGP), Northwest Territories, over two notable climate cycles during the Holocene period (last 11,700 years). Preliminary results indicate the highest arsenic concentrations are found in close proximity to the tailings confinement area. At depth solid-phase arsenic concentrations are higher in non-impacted lakes (Control Lake: 110 mg/kg) than in lakes impacted by mine tailings seepage (Powder Mag: 65 mg/kg, Bulldog: 45 mg/kg). In addition, a gradual increase in dissolved arsenic concentrations with depth is observed in lakes un-impacted by mining activities. These findings will direct the subsequent steps of this project and aid in determining the extents of historical mining impacts and the influence of climate-related variables on the mobility of arsenic within sub-arctic lacustrine systems.