none 10.1190/geo2021-0199.1 Society of Exploration Geophysicists Society of Exploration Geophysicists 186 133050447 5981 2025121211201908500 10.1190 2025-12-12T16:20:27Z 2021-12-16T07:53:19Z 2 Geophysics 0016-8033 1942-2156 03 01 2022 87 2 Reza Mir Laurentian University 1 , Harquail School of Earth Sciences, Sudbury, Ontario P3E 2C6, Canada. reza.mir@gmail.com (corresponding author) http://orcid.org/0000-0001-6463-8263 Peter Fullagar Fullagar Geophysics Pty Ltd 2 , Blackmans Bay 7052, Australia. peter@fullagargeophysics.com . http://orcid.org/0000-0001-9691-850X Mehrdad Darijani Memorial University of Newfoundland 3 , Department of Earth Sciences, St. John’s, Newfoundland A1B 3X7, Canada. m.darijani@mun.ca . Richard Smith Laurentian University 1 , Harquail School of Earth Sciences, Sudbury, Ontario P3E 2C6, Canada. rssmith@laurentian.ca . http://orcid.org/0000-0003-2307-6529 Shawn Scott University of Waterloo 4 , Department of Earth and Environmental Sciences, Waterloo, Ontario N2L 3G1, Canada. shawn.scott@uwaterloo.ca Martin Ross University of Waterloo 4 , Department of Earth and Environmental Sciences, Waterloo, Ontario N2L 3G1, Canada. maross@uwaterloo.ca Pejman Shamsipour Polytechnique Montréal 5 , Department of Civil, Geological and Mining Engineering, Montreal, Quebec H3C 3A7, Canada. pejman.shamsipour@gmail.com Michel Chouteau Polytechnique Montréal 5 , Department of Civil, Geological and Mining Engineering, Montreal, Quebec H3C 3A7, Canada. michel.chouteau@polymtl.ca . http://orcid.org/0000-0002-8538-1775 Kevin Ansdell University of Saskatchewan 6 , Department of Geological Sciences, Saskatoon, Saskatchewan S7N 5E2, Canada. kevin.ansdell@usask.ca http://orcid.org/0000-0002-0911-8537 Mohamed Gouiza University of Saskatchewan 7 , Department of Geological Sciences, Saskatoon, Saskatchewan S7N 5E2, Canada and , School of Earth and Environment, Leeds LS2 9JT, UK. m.gouiza@leeds.ac.uk University of Leeds 7 , Department of Geological Sciences, Saskatoon, Saskatchewan S7N 5E2, Canada and , School of Earth and Environment, Leeds LS2 9JT, UK. m.gouiza@leeds.ac.uk http://orcid.org/0000-0001-5438-2698 ABSTRACT Detection and assessment of the deeply buried high-grade uranium deposits in the Athabasca Basin rely on geophysical methods to map conductive rocks. Variable Quaternary surface cover can mask the anomalous signals from depth and affect the interpretation of inverted conductivity models. We present the analysis of several electromagnetic (EM) modeling studies and two field data sets to demonstrate the effects of varying Quaternary cover resistivity and thickness, on the ability to resolve the parameters of underlying sandstone, alteration, and basement conductors. Synthetic data, assuming a typical shallow EM sounding system and realistic resistivities found in the Athabasca Basin, indicate that resistivity and thickness parameters of the Quaternary cover can be separately recovered in cases in which this cover is more conductive than the underlying sandstone, but not when the cover is significantly more resistive. A 3D modeling study indicates that by using airborne EM data, it is possible to detect a basement conductor of 20 S at a depth of at least 600 m below the surface, even in the presence of Quaternary cover thickness variations of the up to 20% (40–60 m). Furthermore, although Quaternary cover variations and deeper sandstone alteration can produce comparable anomalous signal amplitudes in a time-domain EM response, their effects are most visible in distinctly separate time windows. Ground-penetrating radar and other data to characterize the Quaternary cover in the McArthur River area indicate that this cover consists mostly of sandy tills ranging in thickness from 0 to 117 m. Constrained 3D inversion of an airborne EM data set from the same area indicates basement conductors consistent with the depth and location of a known fault. 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