| Titre | Assembly of the Paleoproterozoic core of Laurentia: new results from the Churchill Province and its bounding orogens |
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| Auteur | Martel, E; Pehrsson, S J; Berman, R G ; Davis, W J; Hamilton, M A;
Sanborn-Barrie, M; White, J C |
| Source | Joint Assembly, AGU-GAC-MAC-CGU, abstracts listing/Réunion conjointe, AGC-AGU-AMC-UGC, abstracts listing; Association géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme
et résumés vol. 38, 2015 p. 373-374  Accès ouvert |
| Liens | Online - En ligne (complete
volume, volume complet, PDF, 10.7 MB)
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| Année | 2015 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190435 |
| Éditeur | Association géologique du Canada |
| Réunion | AGU-GAC-MAC-CGU Joint Assembly; Montréal, QC; CA; mai 3-7, 2015 |
| Document | publication en série |
| Lang. | anglais |
| Media | en ligne; numérique |
| Formats | pdf |
| Sujets | Laurentie; Province de Churchill ; géochronologie; tectonique; Sciences et technologie; Nature et environnement |
| Programme | GEM2 : La géocartographie de l'énergie et des minéraux Géologie du substratum rocheux et des dépôts meubles du sud de la province de Rae |
| Diffusé | 2015 05 01 |
| Résumé | (disponible en anglais seulement)
Integration of over sixty new U-Pb isotopic ages from the Churchill Province and its bounding orogens yields new insights and questions about the assembly of
Laurentia as part of Earths first supercontinent Nuna. A transect across the Thelon Tectonic Zone (TTZ) from the Mesoarchean Queen Maud block finds the latter reworked during Arrowsmith and Thelon orogenesis and the former characterized by a major
2.03-1.99 Ga magmatic and thermal pulse. A widespread 1.91 Ga thermal event is also recognized. The TTZ appears structurally complex, with imbricated slices of Mesoarchean basement and differing Paleoproterozoic crustal levels possibly due to
thick-skinned thrusting also involving the adjacent Slave Province. Previous models of an east-facing rift margin on the Slave, now possibly coeval with the start of TTZ subduction, raise questions about subduction polarity, microcontinent formation
and the heretofore simple Slave-Rae collisional interface. Other Churchill studies reveal a Paleoproterozoic lower crustal domain stretching from Athabasca basin to Hudson strait and characterized by 8- 12 kbar paleopressures in both Archean
basement and Paleoproterozoic supracrustal rocks. A transect of this domain in the NWT reveals a shallowly-dipping crustal stack of 2.7-2.0 Ga ortho- and paragneisses transected by ductile shear zones and blastomylonites. Archean rocks record
MacQuoid and Arrowsmith tectonometamorphism at MPHT conditions. U-Pb metamorphic zircon ages (ca. 1.88 Ga and 1.83 Ga) in 2.3- 2.0 Ga magmatic rocks show that regional 10-12 kbar assemblages (Grt- Cpx; Grt-Hbl) are Paleoproterozoic. Exhumation of
the lower crust was largely complete by ca. 1.82 Ga when ultrapotassic volcano-sedimentary rocks were deposited in transtensional basins. The scale and character of the Churchill-wide lower crustal domain is reminiscent of the Western Gneiss region
of Norway and consistent with others formed worldwide during major collision-accretion events. |
| GEOSCAN ID | 321710 |
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