Evaluation of a rapid, cost effective method to determine geochemical baseline in a legacy mining camp

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The TerraX Minerals Inc. Yellowknife City Gold Project, adjacent to the world-class Giant (1945-2004; 8.1 million oz.) gold mine, has real potential to host an economic ore deposit. The company must thus anticipate any environmental regulatory processes prior to mine development. Historical mineral processing and waste disposal practices created substantial environmental contamination (e.g. highly toxic and bioaccessible arsenic trioxide, As2O3). The TerraX property encompasses rocks with naturally elevated metal concentrations though. Elevated levels of As and other metals in lakes throughout their claims could result from any combination of natural weathering, past mining activities, or metal remobilization due to land-use changes. It is critical that geochemical baseline and past land-use impacts on lakes within the claims, currently lacking, be defined prior to mine development. The research challenge is to define geochemical baseline for selected lakes against which future TerraX land-use impacts can be assessed. The only previous high-resolution geochemical study carried out to date in the north was by my group at Matthews Lake, NT. We propose to use a new technique that builds on the Matthews Lake results. We will continue using a coring methodology where sediments are frozen in situ and extracted, thus eliminating disturbance of lake sediments caused by traditional coring devices. We will test an alternative analytical method with the potential to dramatically reduce analytical costs and throughput times. At Matthews lake we sliced the frozen sediment cores at mm-scale using our custom designed microtome, to achieve a temporal sampling resolution equivalent to a sample every 2-10 years, and analyzed the sample for their metal content using ICP-MS analysis. For the proposed research instead of slicing cores we will non-destructively scan them at 0.2 mm (annual) resolution using a newly available ITRAX XRF scanner at McMaster University. With this new approach we will make a major (order of magnitude) step in improving throughput and affordability of core analysis required to determine geochemical baseline and the rate of change of contaminants over time, a significant step forward in Canadian environmental stewardship.