Till Geochemical and Heavy Mineral Signatures of the Kiggavik Uranium Deposit, Nunavut, Canada
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Mineral exploration in glaciated terrain has successfully utilized till geochemistry and indicator mineral methods for diamonds and gold. More recently, methods for base metals and other commodities have been developed, however, few published cased studies have documented the glacial dispersal from uranium (U) deposits using indicator minerals and till geochemistry. In response to the need to develop surficial exploration methods to help discover drift covered U deposits, this study was conducted to document and interpret the mineralogical and geochemical signature of the Kiggavik U deposit and its glacial dispersal. The study area is within the zone affected by the migration of the Keewatin Ice Divide of the Laurentide Ice Sheet. Surface till samples (n=71) were collected directly overlying, up-ice and down-ice from the deposit with respect to the dominant north-northwest, northwest, and west ice flow directions. Till samples containing the highest metal contents were located directly to the west of the deposit in locally derived, basement-dominated grey till. Till geochemistry exhibits a polymetallic dispersal signature down-ice of the Kiggavik Main Zone (KMZ) outcrop. Uranium, Bi, Mo, Au, Ag, Co, Cs, Pb and W range from elevated to anomalously high concentrations up to 1 km down-ice of the KMZ and thus can be utilized as pathfinder elements. These pathfinder elements are also present down-ice from other U deposits within the Kiggavik camp, demonstrating their broad applicability to U exploration in basement rocks near the Thelon Basin. Laboratory gamma-ray spectrometry and Pb isotopic analysis were conducted on the till samples and show that eU and Pb isotope ratios in the till matrix share a strong correlation with U content in till. Heavy mineral picking of the sand-sized till fraction did not return any U bearing minerals as they are not physically and chemically resistant to post glacial weathering. However, elevated gold grains counts were encountered and can be used as an indicator for U mineralization. Lead rich apatites grains (up to 8% Pb) were discovered in mineralized bedrock and these are of particular interest due to their rarity and potential to be a an indicator mineral for such deposits, provided that new techniques to quantitatively separate and analyze the finer fraction of the HMC be can be developed.