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TitleGeophysical inversion contributions to mineral exploration: lessons from the Footprints project
AuthorVallée, M A; Morris, W A; Perrouty, S; Lee, R G; Wasyliuk, K; King, J J; Ansdell, K; Mir, R; Shamsipour, P; Farquharson, C G; Chouteau, M; Enkin, R JORCID logo; Smith, R S
SourceGeophysics applied to mineral exploration; by Pinet, N (ed.); Gloaguen, E (ed.); Giroux, B (ed.); Canadian Journal of Earth Sciences vol. 56, no. 5, 2019 p. 525-543,
Alt SeriesNatural Resources Canada, Contribution Series 20190112
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
ProvinceQuebec; Saskatchewan; British Columbia
NTS32C/04; 32D/01; 74A; 74B; 74G; 74H; 74I; 92I/02; 92I/03; 92I/06; 92I/07; 92I/10; 92I/11
AreaMalartic; McArthur River; Kamloops
Lat/Long WENS -78.2667 -77.9833 48.1833 48.0167
Lat/Long WENS-106.5000 -104.5000 58.2500 56.7500
Lat/Long WENS-121.2500 -120.8333 50.6167 50.1833
Subjectseconomic geology; geophysics; Science and Technology; mineral deposits; gold; copper; uranium; mineral exploration; exploration methods; geophysical surveys; geophysical interpretations; gravity models; densities; magnetic modelling; magnetic susceptibility; modelling; models; mapping techniques; bedrock geology; lithology; structural features; petrophysics; Canadian Malartic Deposit; Highland Valley Copper Deposit; McArthur River Deposit; Millennium Deposit; Piché Group; Fournière Batholith; Guichon Creek Batholith; Athabasca Basin; Methodology; Data processing
Illustrationslocation maps; geoscientific sketch maps; tables; 3-D models; 3-D images; models
Released2019 04 18
AbstractMagnetic and gravity inversions are used to create 2D or 3D models of the magnetic susceptibility and density, respectively, using potential field data. Unconstrained inversions generate an output based on mathematical constraints imposed by the inversion algorithm. Constrained inversions integrate lithological, structural, and petrophysical information in the inversion process to produce more geologically meaningful results. This study analyses the validity of this assertion in the context of the NSERC-CMIC Mineral Exploration Footprints project. Unconstrained and constrained geophysical inversions were computed for three mining sites: a gold site (Canadian Malartic, Québec), a copper site (Highland Valley, British Columbia), and a uranium site (Millennium-McArthur River, Saskatchewan). After initially computing unconstrained inversions, constrained inversions were developed using physical property measurements, which directly link geophysics to geology, and lithological boundaries extracted from an interpreted geological model. While each derived geological model is consistent with the geophysical data, each site exhibited some magnetic complexity that confounded the inversion. The gold site includes regions with a strong magnetic signature that masks the more weakly magnetic zone, thereby hiding the magnetic signature associated with the ore body. Initial unconstrained inversions for the copper site yielded solutions with invalid depth extent. A consistency between the constrained model and the geological model is reached with iterative changes to the depth extent of the model. At the uranium site, the observed magnetic signal is weak, but the inversion provided some insights that could be interpreted in terms of an already known complexly folded geological model.

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