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TitleThe 3-dimensional construction of the Rae craton, central Canada
AuthorSnyder, D B; Craven, J A; Pilkington, M; Hillier, M J
SourceGeochemistry, Geophysics, Geosystems (G3) 16, 2015 p. 3555-3574,
Alt SeriesEarth Sciences Sector, Contribution Series 20150111
PublisherAmerican Geophysical Union
Mediaon-line; digital
File formatpdf
NTS46; 47A; 47B; 47C; 47D; 55J; 55K; 55L; 55M; 55N; 55O; 55P; 56; 57A; 57B; 57C; 57D
AreaMelville Peninsula; Boothia Peninsula; Baker Lake; Rankin Inlet
Lat/Long WENS-96.0000 -80.0000 70.0000 62.0000
Subjectstectonics; geophysics; Archean; craton; modelling; bedrock geology; gravity; seismic interpretations; discontinuities; shear zones; radiometric dating; kimberlites; lithology; tonalites; trondhjemites; granodiorites; pyroxenites; orogenesis; faults, thrust; metasomatism; magnetic interpretations; conductivity; Mohorovicic discontinuity; Rae craton; Hudsonian orogeny
ProgramRae Province Project Management, GEM2: Geo-mapping for Energy and Minerals
AbstractReconstruction of the 3-dimensional tectonic assembly of early continents, first as Archean cratons and then Proterozoic shields, remains poorly understood. In this paper, all readily available geophysical and geochemical data are assembled in a 3-D model with the most accurate bedrock geology in order to understand better the geometry of major structures within the Rae craton of central Canada. Analysis of geophysical observations of gravity and seismic wave speed variations revealed several lithospheric-scale discontinuities in physical properties. Where these discontinuities project upward to correlate with mapped upper crustal geological structures, the discontinuities can be interpreted as shear zones. Radiometric dating of xenoliths provides estimates of rock types and ages at depth beneath sparse kimberlite occurrences. These ages can also be correlated to surface rocks. The 3.6--2.6 Ga Rae craton comprises at least three smaller continental terranes, which "cratonized" during a granitic bloom. Cratonization probably represents final differentiation of early crust into a relatively homogeneous, uniformly thin (35--42 km), tonalite-trondhjemite-granodiorite crust with pyroxenite layers near the Moho. The peak thermotectonic event at 1.86--1.7 Ga was associated with the Hudsonian orogeny that assembled several cratons and lesser continental blocks into the Canadian Shield using a number of southeast-dipping megathrusts. This orogeny metasomatized, mineralized, and recrystallized mantle and lower crustal rocks, apparently making them more conductive by introducing or concentrating sulfides or graphite. Little evidence exists of thin slabs similar to modern oceanic lithosphere in this Precambrian construction history whereas underthrusting and wedging of continental lithosphere is inferred from multiple dipping discontinuities.
Summary(Plain Language Summary, not published)
This paper describes a 3-dimensional model encompassing a volume of the Earth down to 300 km in central Nunavut. The region covered is between the northern communities of Baker Lake, Kugaruk, Repulse Bay and Rankin Inlet. Several geophysical data sets and derived 3-D models have been assembled: these include gravity gradients, P-wave speeds, surface wave speeds, conductivity, and receiver functions. These data and models are geo-registered with the GEM Tri-territorial geological map compilation. The 3-D models and their interpretation provide context and insights into the locations and sources of known diamond and gold deposits in this region as well as into the structure geometries associated with the tectonic construction of this ancient part of Canada.