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TitleLithospheric architecture of the Slave craton, northwest Canada, as determined from an interdisciplinary 3-D model
AuthorSnyder, D B; Hillier, M J; Kjarsgaard, B A; de Kemp, E A; Craven, J A
SourceGeochemistry, Geophysics, Geosystems (G3) vol. 15, 2014 p. 1-16,
Alt SeriesEarth Sciences Sector, Contribution Series 20130298
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut; Northwest Territories
NTS75E; 75I; 75J; 75K; 75L; 75M; 75N; 75O; 75P; 76; 77A; 77B; 85F; 85G; 85H; 85I; 85J; 85K; 85N; 85O; 85P; 86A; 86B; 86C; 86F; 86G; 86H; 86I; 86J; 86K; 86N; 86O; 86P
Lat/Long WENS-117.0000 -105.0000 69.0000 61.0000
Subjectstectonics; lithosphere; models; modelling; mapping techniques; gold; mineralization; Archean; craton; metasomatism; Slave Craton
Illustrationslocation maps; models; plots
ProgramDiamonds, GEM: Geo-mapping for Energy and Minerals
Released2014 05 29
AbstractRegional-scale geologic structures characteristic of mantle lithosphere within cratons found in continent interiors are interpreted using geo-registered diverse data sets from the Slave craton of northwest Canada. We developed and applied a new method for mapping seismic discontinuities in three dimensions using multiyear observations at sparse, individual broadband receivers. New, fully 3-D conductivity models used all available magnetotelluric data. Discontinuity surfaces and conductivity models were geo-registered with previously published P-wave and surface-wave velocity models to confirm first-order structures such as a midlithosphere discontinuity. Our 3-D model to 400 km depth was calibrated by ''drill hole'' observations derived from xenolith suites extracted from kimberlites. A number of new structural discontinuities emerge from direct comparison of coregistered data sets and models. Importantly, we distinguish primary mantle layers from secondary features related to younger metasomatism. Subhorizontal Slave craton layers with tapered, wedge-shaped margins indicate construction of the craton core at 2.7 Ga by underthrusting and flat stacking of lithosphere. Mapping of conductivity and metasomatism in 3-D, the latter inferred via mineral recrystallization and resetting of isotopic ages in xenoliths, indicates overprinting of the primary layered structures. The observed distribution of relatively conductive mantle at 100-200 km depths is consistent with pervasive metasomatism; vertical ''chimneys'' reaching to crustal depths in locations where kimberlites erupted or where Au mineralization is known.
Summary(Plain Language Summary, not published)
The GEM program was designed to map Canada's North. In order to support diamond exploration, this mapping is best done at 150-300 km depths, the so-called 'diamond window'. Fully three-dimensional mapping using geophysical methods, as calibrated by rare rock and garnet samples from these depths is required. A regional 3-D model now exists for the ancient Slave province within the Canadian Shield and can be presented in stereo using gOcad software. The Slave region of northwest Canada has undergone relatively intense exploration by the diamond industry so that geochemistry of the mantle can be estimated where diamond-bearing kimberlite volcanic deposits have been discovered and studied. Observed or modelled geophysical properties can thus be calibrated or 'ground truthed' in these sparse locations and extrapolated outward across North America. Our new 3-D models place this 'spot', 1-D geochemical information into a fuller context on a continental-wide scale and allow comparisons with similar ancient terranes on other continents. New insights may suggest new avenues for exploration.