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The development of surface geochemical technologies for the detection of kimberlites concealed by glacial drift in the Northwest Territories, Canada Cayer, Erika Mary

Abstract

Many diamondiferous kimberlites in the Lac de Gras region of the Northwest Territories are concealed by several metres of glacial drift and are therefore challenging to detect by traditional exploration techniques. Soil samples were collected in a 50x60 metre grid crossing the DO-18 kimberlite (Peregrine Diamonds Ltd.), concealed by 5-20 metres of glacial sediments, to evaluate the potential of surface geochemical target discrimination techniques to detect the presence of a kimberlite through cover. Physicochemical measurements were recorded at each sample site, and soil samples were analysed by ICP-MS following 4-Acid, Aqua Regia and De-Ionized Water digestions, as well as field portable X-Ray Fluorescence (fp-XRF), spatiotemporal geochemical hydrocarbons (SGH), and select samples by X-Ray Diffraction (XRD) and Sequential Leach. AGI Inc. Goresorber™ Hydrocarbon Collectors were also installed at each site. Surficial material, soil type, topographic variation and vegetation were mapped to give insight to the influences of geomorphological processes on geochemistry. An east-west trending slope break divides the research site into a topographically high region in the north, and a low-lying region in the south. The north consists of till, and the south comprises till, organics and glaciofluvial and glaciolacustrine sediments. 4-Acid and Aqua Regia digestion data display a dispersal of Cr, Mg, Nb, and Ni from directly above the kimberlite in the north, to the edge of the sampling grid, in the down-ice direction. Fp-XRF data exhibits a similar distribution in all elements except Mg, as does SGH data in light benzenes. Ni and Mg concentrations in the kimberlite demonstrate that it is the source of the geochemical anomalies. Glacial transport is hypothesized to have generated the geochemical anomalies, and glaciolacustrine and glaciofluvial processes are considered to have generated the lower topography and diluted the geochemical responses in the south.

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