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TitleLithotectonic framework of the Core Zone, southeastern Churchill Province, Canada
AuthorCorrigan, D; Wodicka, N; McFarlane, C; Lafrance, I; van Rooyen, D; Bandyayera, D; Bilodeau, C
SourceGeoscience Canada vol. 45, no. 1, 2018 p. 1-24,
Alt SeriesNatural Resources Canada, Contribution Series 20180058
PublisherGeological Association of Canada
Mediapaper; on-line; digital
File formatpdf
ProgramHudson/Ungava Core Zone, GEM2: Geo-mapping for Energy and Minerals
Released2018 03 01
AbstractThe Core Zone, a broad region located between the Superior and North Atlantic cratons and predominantly underlain by Archean gneiss and granitoid rocks, remained until recently one of the less well known parts of the Canadian Shield. Previously thought to form part of the Archean Rae Craton, and later referred to as the Southeastern Churchill Province, it has been regarded as an ancient continental block trapped between the Paleoproterozoic Torngat and New Quebec orogens, with its relationships to the adjacent Superior and North Atlantic cratons remaining unresolved. The geochronological data presented herein suggest that the Archean evolution of the Core Zone was distinct from that in both the Superior and North Atlantic (Nain) cratons. Moreover, the Core Zone itself consists of at least three distinct lithotectonic entities with different evolutions, referred to herein as the George River, Mistinibi-Raude and Falcoz River blocks, that are separated by steeply-dipping, crustal-scale shear zones interpreted as paleosutures. Specifically, the George River Block consists of ca. 2.70 Ga supracrustal rocks and associated ca. 2.70-2.57 Ga intrusions. The Mistinibi-Raude Block consists of remnants of a ca. 2.37 Ga volcanic arc intruded by a ca. 2.32 Ga arc plutonic suite (Pallatin) and penecontemporaneous alkali plutons (Pelland and Nekuashu suites). It also hosts a coarse clastic cover sequence (the Hutte Sauvage Group) which contains detrital zircons provided from locally-derived, ca. 2.57-2.50 Ga, 2.37-2.32 Ga, and 2.10-2.08 Ga sources, with the youngest concordant grain dated at 1987 ± 7 Ma. The Falcoz River Block consists of ca. 2.89-2.80 Ga orthogneiss intruded by ca. 2.74-2.70 granite, tonalite, and granodiorite. At the western margin of the Core Zone, the George River Block and Kuujjuaq Domain may have been proximal by ca. 1.84 Ga as both appear to have been sutured by the 1.84-1.82 Ga De Pas Batholith, whereas at its eastern margin, the determination of metamorphic ages of ca. 1.85 to 1.80 Ga in the Falcoz River Block suggests protracted interaction with the adjacent Lac Lomier Complex during their amalgamation and suturing, but with a younger, 'New Quebec' overprint as well. The three crustal blocks forming the Core Zone add to a growing list of 'exotic' Archean to earliest Paleoproterozoic microcontinents and crustal slices that extend around the Superior Craton from the Grenville Front through Hudson Strait, across Hudson Bay and into Manitoba and Saskatchewan, in what was the Manikewan Ocean realm, which closed between ca. 1.83-1.80 Ga during the formation of supercontinent Nuna.
Summary(Plain Language Summary, not published)
This paper presents 20 new radiogenic isotope ages (U-Pb on zircon) that permit the subdivision of the Core Zone (part of Labrador and Northeastern Quebec) into three separate micro-continents or crustal blocks separated by sutures. These three blocks were tectonically amalgamated about 1.83 billion years ago during convergence between the Superior and North Atlantic cratons.