Ground truthing of the 'Eastern Athabasca Basin' regional airborne gamma-ray survey: context for exploration of deeply buried unconformity-related uranium deposits in the Athabasca Basin of northern Saskatchewan

Abstract

With uranium exploration shifting to greater depths and more indirect targets, new tools and better use of existing data are needed to maximize exploration efficiency. Recent and historical research has demonstrated that although deeply-buried beneath Athabasca Group sandstones, unconformity-related uranium deposits still may be targeted by understanding subtle surficial geochemical anomalies. Airborne gamma-ray spectrometric surveys can be used for effective surficial geochemical mapping of K, U and Th over large areas and have been conducted by the Geological Survey of Canada across much of the Canadian Shield over the past 50 years, notably in partnership with Saskatchewan over the Athabasca Basin. To apply the results of these surveys to uranium exploration, the effects of deposit-related geochemical anomalies on airborne gamma-ray measurements must be predicted. And, just as importantly, the background in terms of K, U and Th above which these anomalies have to be detected, has to be quantified and its genetic linkages understood. The "Eastern Athabasca Basin" airborne gamma-ray survey was conducted in partnership with the Saskatchewan Geological Survey in 2009. This regional survey was ground-truthed along the corridor between Key Lake and the McArthur River mine site in 2013. High-resolution helicopter-borne gamma-ray acquisition, ground gamma-ray spectrometry, surficial material mapping, sampling and laboratory analyses were performed. Results indicate that the relationships between subsurface processes, glacial dispersal and airborne gamma-ray measurements are very intricate and responsive to detailed local surficial geological processes that have modified elemental dispersion from bedrock sources. In many cases, surficial sediments and landforms can be discriminated based on their K, U and Th geochemistry, relating in turn, to their provenance. Quantitative analysis of the airborne data, integrated with surficial geological knowledge, can differentiate between the complex patchwork of background domain levels and deposit-related surficial geochemical anomalies.