Geochemical Characterization and Reactive Transport Simulation of Metal Leaching and Acid Generation in Waste Rock from the Ekati Diamond Mine, NT

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Mining activities generate significant quantities of waste materials, which can negatively impact water and soil quality, and the health of receiving ecosystems. Weathering of sulfide-bearing mine wastes, including uneconomic waste rock, can generate acidic drainage and promote the release of inorganic constituents, including metal(loid)s and sulfate. The Ekati Diamond Mine is located approximately 300 km northeast of Yellowknife, NWT. Ekati will generate ~820 MT of waste rock, including ~50 MT of waste rock from the Pigeon Open Pit, which is comprised primarily of mixed metasediment and granite-diabase. Under field conditions, the material is of uncertain acid-generating potential; this finding differs from results of laboratory-scale humidity-cell tests conducted using core-sample charges, which classified the rock as potentially acid generating. The scope of the proposed research project is to re-assess the acid-generating and metal-leaching potential of waste rock from the Pigeon Pit through an integrated program of field-sample collection, laboratory experimentation and characterization, and reactive transport modelling. The proposed project will provide critical insights into the potential long-term water-quality impacts that may arise from waste-rock weathering, and develop scaling relationships to predict contaminant release, transport, and attenuation in the field; these outcomes will be integrated by Ekati into closure planning and cover design.