Till geochemical signatures of the Kiggavik uranium deposit, Nunavut

Abstract

In 2010, a drift prospecting study was initiated over the Kiggavik uranium deposit under the Geomapping for Energy and Minerals (GEM) Program. The objective of this study was to document the till geochemical signatures of the Kiggavik uranium deposit and to apply these geochemical characteristics for future exploration for buried, drift-covered uranium deposits. The study area is within the zone affected by the migration of the Keewatin Ice Divide of the Laurentide Ice Sheet. Mineralized bedrock and surface till samples (n=71) were collected directly overlying, up-ice, and at various distances (50 m, 100 m, 200 m, 500 m, 1 km, 2 km, 3 km, 5 km, and 10 km) in a fan-shaped pattern down-ice from the deposit with respect to the dominant north-northwest, northwest, and west ice-flow directions. Samples containing the highest metal contents were located directly to the west of the deposit in locally derived, basement-dominated grey till, which markedly contrasts with the regional red till dominated by material eroded from the Baker Lake and Wharton Groups of the Dubawnt Supergroup. Till geochemistry exhibits a polymetallic dispersal signature down-ice of the Kiggavik Main Zone 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 Main Zone 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. Analysis of the <0.063 mm and <0.002 mm fraction of the till matrix shows that elemental abundances are significantly greater in the finer fraction, indicating a strong geochemical partitioning based on grain size. Laboratory gamma-ray spectrometry, Pb isotopic analysis, and X-ray diffraction were conducted on the till samples. Results show that eU and Pb isotope ratios (206Pb/204Pb, 207Pb/204Pb, 207Pb/206Pb) in the till matrix share a strong correlation with U content in till and can be used as a geochemical tool for U exploration. The clay mineralogy of samples with elevated to anomalously high U is enriched in illite and kaolinite relative to quartz. Pebble lithological and Pb isotope ratio analyses have trends that can be applied to deciphering till matrix provenance.

Geochemistry of magnetite and hematite from unmineralized bedrock and local till at the Kiggavik uranium deposit: Implications for sediment provenance

“…is intimately associated with intense clay mineral alteration halos. The alteration halos comprise desilicification, replacement of feldspar and mica by illite/sericite and chlorite, and strong oxidation-reduction features, especially in sulfide-rich rocks (Pacquet, 1993;Robinson et al, 2014;Sharpe et al, 2015). Marcasite and pyrite are the most common sulfide minerals in association with uraninite and coffinite, the main ore minerals in the dominantly monometallic Kiggavik deposits.…”

“…Marcasite and pyrite are the most common sulfide minerals in association with uraninite and coffinite, the main ore minerals in the dominantly monometallic Kiggavik deposits. The surficial geology of the Kiggavik area is characterized by an absence of eskers and ribbed moraines (Aylsworth and Shilts, 1989), and a ubiquitous cover of till (McMartin et al, 2006;Robinson et al, 2014). At Kiggavik, there is about 10% bedrock exposure, typically Ketyet Group quartzite, Neoarchean basement granitic gneiss, or Hudson granitic rocks that are exposed only in hills (Robinson, et al, 2014).…”

“…The surficial geology of the Kiggavik area is characterized by an absence of eskers and ribbed moraines (Aylsworth and Shilts, 1989), and a ubiquitous cover of till (McMartin et al, 2006;Robinson et al, 2014). At Kiggavik, there is about 10% bedrock exposure, typically Ketyet Group quartzite, Neoarchean basement granitic gneiss, or Hudson granitic rocks that are exposed only in hills (Robinson, et al, 2014). Thin layers of till (<2 m) cover bedrock highs and resistant bedrocks, whereas till blankets (2-25 m thick) and hummocky till dominate in lower lying areas, and overlying less-resistant metasedimentary rocks (Robinson et al, 2014).…”

“…At Kiggavik, there is about 10% bedrock exposure, typically Ketyet Group quartzite, Neoarchean basement granitic gneiss, or Hudson granitic rocks that are exposed only in hills (Robinson, et al, 2014). Thin layers of till (<2 m) cover bedrock highs and resistant bedrocks, whereas till blankets (2-25 m thick) and hummocky till dominate in lower lying areas, and overlying less-resistant metasedimentary rocks (Robinson et al, 2014). Faceted and striated surfaces that indicate multiple ice-flow trajectories characterize the Ketyet quartzite exposures to the north of the Kiggavik deposits (Robinson, et al, 2014).…”

Basement geology beneath the northeast Thelon Basin, Nunavut: insights from integrating new gravity, magnetic and geological data

“…Glacial till generally less than 10 m thick, but thicker in drumlins, covers all but 2% of the region and is tran-sected by eskers mainly in the northern and western parts of the study area (McMartin and Dredge 2005;LaRocque et al 2012;Robinson et al 2014). A single outlier of Ordovician dolostone (Fig.…”