The Carleton University GeoSoc presents...
Integrated ITRAX-XRF and freeze coring as a method for high quality, rapid, and cost effective determination of baseline levels for elements of concern
Braden Gregory, Ph.D. student
Thursday, March 9th
To ensure sustainable resource development, the Northwest Territorial government established the “Mine Site Reclamation Policy”, which stipulates that companies must present detailed mine site remediation plans prior to the initiation of mining operations. Defining baseline concentrations for elements of concern (EOC) is integral for returning impacted systems to their natural state. This is challenging due to naturally elevated concentrations of EOC in bedrock, the presence of contamination from historical mining practices, and the environmental response of natural systems to climate variability. Lake systems can be used to establish EOC baseline because they act as a regional sediment sink. However, the low sedimentation rate found in most subarctic lakes results in coarse temporal resolution (centuries) when using traditional geochemical analysis (e.g., ICP-MS) due to high weight-per-sample requirements. To resolve this issue of resolution, we combine freeze-coring, a method that can reliably captures the sediment-water interface of lakes, with Itrax core-scanning X-ray fluorescence (Itrax-XRF), which can measure the geochemistry of sediments in intact cores at sub-mm resolution. In order for this technique to be relevant to policy makers and mine developers the semi-qualitative results obtained via Itrax-XRF analysis must be calibrated to obtain absolute values. To test calibration methods, one freeze core was recovered from Milner Lake, a lake adjacent to a prospective gold mine ~15 km north of Yellowknife. I tested linear and multivariate calibration models and comment on the relative merits of both techniques, as well as discuss my field experience in the north.