GEOSCAN, résultats de la recherche


TitreThe Arrowsmith orogeny: geochronological and thermobarometric constraints on its extent and tectonic setting in the Rae craton, with implications for pre-Nuna supercontinent reconstruction
AuteurBerman, R G; Pehrsson, S; Davis, W J; Ryan, J J; Qui, H; Ashton, K E
SourcePaleoproterozoic tectonic assembly of the western Canadian shield: new findings and implications for the reconstruction of Laurentia/Nuna; par Berman, R G (éd.); Bethune, K M (éd.); Precambrian Research vol. 232, 2013 p. 44-69,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100390
Documentpublication en série
Mediaen ligne; numérique
ProvinceAlberta; Saskatchewan; Territoires du Nord-Ouest; Nunavut
SNRC55; 56; 57; 65; 66; 75; 76
Lat/Long OENS-112.0000 -88.0000 72.0000 59.0000
Sujetscadre tectonique; datation au uranium-plomb; thermobarométrie; conditions de pression-température; roches métamorphiques; migmatites; métapsammites; faciès métamorphiques; faciès à granulite; gneiss; lithologie; évolution tectonique; Archéen; Craton de Rae ; Orogenèse d'Arrowsmith ; tectonique; géochronologie; Précambrien
Illustrationsanalyses; geological sketch maps
ProgrammeGEM Tri-Territorial Information Management & Dissemination (Data management - Minerals component), GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Geochronological and thermobarometric data for two widely spaced and previously unknown areas of the Rae craton provide important temporal and spatial links between previously studied areas in the northern and southern Rae craton that had been interpreted to have been reworked during the Arrowsmith orogeny. In southern Boothia Peninsula (SBP), upper amphibolite to granulite facies metamorphism is dated by in situ SHRIMP monazite ages of 2.64 - 2.60, 2.54, 2.50 - 2.49 2.44, and 2.38-2.34 Ga, with retrograde monazite growth at 2.27 Ga. SHRIMP zircon ages of two metasedimentary rocks provide a further indication of metamorphism at ca. 2.56 - 2.54 Ga and at ca. 2.50 Ga, which is also the age determined for a K-feldspar augen granite. Textural relationships indicate that regional foliation formed at 2.54 Ga and 2.5 - 2.49 Ga. Peak metamorphic conditions of ~700 °C and 5 - 6 kbar are interpreted to have been quenched during the 2.38 - 2.34 Ga event. In the McCann - McArthur Lake region (MMLR) of the southwestern Rae craton, upper amphibolite to granulite facies metamorphism is dated by in situ SHRIMP monazite ages of ca. 2.53, 2.47, and 2.37 - 2.28 Ga, with retrograde monazite growth at ca. 2.26 Ga. Textural relationships indicate deformation initiated by ca. 2.37 Ga and terminated by ca. 2.30 Ga. Metamorphic conditions between ~5 kbar and 700 - 735 °C were quenched during at ca. 2.3 Ga following peak conditions of ~7 kbar and 800 °C.
The evidence for regional deformation at 2.54 - 2.50 Ga in SBP supports an Andean-type accretionary margin setting for the Arrowsmith orogeny. A collisional event may have terminated high-grade activity in the northern region by ca. 2.35 Ga while metamorphism associated with continental arc magmatism continued in the south until at least ca. 2.28 Ga. The combined data demonstrate the continuity and broad extent of the Arrowsmith orogen along the western flank of the Rae craton, extending from northern Saskatchewan to northern Baffin Island. The broad extent of a globally rare orogenic period provides an important piercing point for supercontinent reconstructions that are discussed in a companion paper. The inferred convergent tectonic activity between ca. 2.5 - 2.28 Ga is interpreted to have occurred on the flank of a growing supercontinent, a setting that would account for an apparent slowdown, but not shutdown in global tectonics.