Eva Yu, MSc
E. Yu1, D. Gregory1, M.A. Reynolds2, S. Viehmann3, S. Weyer3
1Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
2Department of Industry, Tourism, and Investment, Northwest Territories Geological Survey, Yellowknife, Northwest Territories, Canada
3Institute of Earth System Sciences, Leibniz University Hannover, Hannover, Lower Saxony, Germany
Howard’s Pass is located along the Yukon-Northwest Territories border in the Selwyn Basin and hosts 15 sediment hosted massive sulfide deposits (SHMS), a resource yielding >400Mt grading 4.84% Zn. These 15 SHMS deposits are strata bound in the Active Member subunit (ACTM) within siliceous, calcareous, and carbonaceous mudstones of the Ordovician-Silurian Duo Lake Formation (DLF). Throughout the DLF, enrichments of vanadium, up to 2890 ppm, held in clay minerals and organic matter, occur in intervals, and in the footwall of the ACTM. Approximately 80km southeast of Howard’s Pass is the Van Property, at a similar stratigraphic position in the Duo Lake Formation, vanadium, up to 6000 ppm, is found in rutile, clay minerals, and organic matter. Recent studies indicate that vanadium at Howard’s Pass is not hosted in rutile, suggesting that the enrichment may represent either a less evolved form of the mineralization observed at the Van Property or a distal extension of that mineralization system. Although three competing genetic models have been proposed to explain the base metal accumulation in sediments, the sources of metals and their transport pathways remain underexplored in the Howard’s Pass District. This research will focus on the Zn- and V-rich mineralization in the DLF, where we employ geochemical proxies (Fe-speciation, acid volatile sulfides/chromium reducible sulfides, whole rock bulk geochemistry, stable isotopes, and reflected light microscopy, scanning electron microscopy) to infer the paleo-depositional conditions of the metal enrichment. Lithogeochemical analysis on three drill cores across the DLF at HP, indicate intervals enriched with V, U, Mo, and Ni correlating with elevated concentrations of organic matter. These intervals show elevated levels of metal enrichment relative to average shale compositions worldwide. Local episodic euxinia occurs throughout the formation, suggested by the degree of pyritization, reactive iron, and sulfur systematics. Stable isotopes can aid in cross validating and refining these interpretations of redox conditions by determining the extent of euxinia, sulfate reduction, and basin restriction. The results will provide insights into how redox fluctuations during sediment deposition may have impacted metal concentration and preservation in sediment and potentially have broader implications for the understanding of sediment-hosted ore deposits.