Glacial Dispersal of Indicator Minerals from the Izok Lake Zn-Cu-Pb-Ag VMS Deposit, Nunavut, Canada
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Volcanogenic massive sulphide (VMS) deposits have a characteristic geochemical suite of enriched metals, mineralization and related hydrothermal alteration minerals; however, very little research has been carried out to determine which of these minerals may be useful for exploration in glaciated terrains and there are very few case studies in the public realm that document down-ice dispersal of these from known volcanogenic massive sulphide (VMS) deposits. In response to these needs and to refine and optimize surficial exploration methods in northern Canada, this study was conducted to examine the mineralogical signature of the Izok Lake Zn-Cu-Pb-Ag VMS deposit, Nunavut and its glacial till dispersal. Glacial sediments were deposited in the Izok Lake region by the Laurentide Ice Sheet. Detailed ice flow mapping indicates four stages of ice flow (oldest to youngest): 1) southwest (255 ̊); 2) weak flow to the northwest (315 ̊); a dominant ice flow and landform trend to the west-northwest (292 ̊), and 4) northwest (318 ̊) that was only observed east of the Iznogoudh Lake area (Hicken et al., 2011). The till geochemical signature (aqua regia digestion ICP-MS analysis) for the <0.063 mm fraction of the till matrix is defined by elevated (above the 95th percentile) contents of Zn, Cu, Pb, Fe, Ag, Cd, Bi, Hg, Se, In and Tl. These element signatures in till can be detected up to 8 km down-ice from the deposit. Till geochemical data is used to evaluate which till samples are metal-rich and may contain indicator minerals. Indicator minerals for the amphibolite metamorphic grade Izok Lake VMS deposit includes: gahnite, staurolite, axinite, chalcopyrite, sphalerite and pyrite. Sulphide minerals are present at lower abundances than gahnite and staurolite as they are not physically and chemically as robust/resistant during postglacial weathering. Gahnite is the most useful VMS indicator mineral in the postglaciated Izok Lake area, as it was readily identified in till heavy mineral concentrates, it is abundant (100 of grains), its chemically stable in the surficial weathering environment, and can be detected up to 40 km down-ice. This study is one of the first to document indicator minerals down-ice from a VMS deposit in a postglaciated terrain.