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TitleMagnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada
AuthorSpratt, J E; Skulski, T; Craven, J A; Jones, A G; Snyder, D B; Kiyan, D
SourceJournal of Geophysical Research, Solid Earth vol. 119, 2014 p. 2415-2439,
Alt SeriesEarth Sciences Sector, Contribution Series 20130056
PublisherAmerican Geophysical Union
Mediapaper; on-line; digital
File formatpdf
NTS56; 46J; 46K; 46L; 46M; 46N; 46O; 46P; 47A; 47B; 57A; 57B
AreaMelville Peninsula; Committee Bay; Boothia Peninsula; Wager Bay; Repulse Bay
Lat/Long WENS-98.0000 -80.0000 70.0000 63.0000
Subjectsgeophysics; magnetotelluric surveys; magnetotelluric data; magnetotelluric interpretations; resistivity; lithosphere; basement geology; bedrock geology; conductivity; models; modelling; Rae Craton
Illustrationslocation maps; profiles
ProgramDiamonds, GEM: Geo-mapping for Energy and Minerals
AbstractNew magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of>300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from ~3000 omega m in the northeast (beneath Baffin Island and the Melville Peninsula) to ~10,000 omega m beneath the central Rae craton, to >50,000 omega m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of ~500 omega m at depths of 180-220km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.
Summary(Plain Language Summary, not published)
New geophysical (magnetotelluric) soundings at 64 locations throughout the central Nunavut enabled new 2-dimensional modelling of the Earth's electrical conductivity to at least 300 km depth. This region has undergone recent intense diamond exploration, results with which to help understand the new conductivity models. Conductors indicate that surface units typically hosting gold probably extend deep into the crust and that the deeper conductors divide blocks of differing ages and thus presumed different diamond prospectivity.