Gravimetric transect of eastern Ungava Bay, northern Torngat Orogen.

• Main Authors: Seguin, Maurice K., Goulet, Normand
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Association of Canada 1990
• Subjects: Ungava Bay; Rivière George; Lake Harbour; Keglo Bay; Baie d'Ungava
• Online Access: https://journals.lib.unb.ca/index.php/GC/article/view/3703

Detailed gravity data, collected in the northern part of Québec along a SW-NE transect across the northern Torngat Orogen, provide constraints on the deep structure of this segment of the orogen. The section, located in the Rae Province east of Ungava Bay, traverses the Archean gneissic terrane of the George River segment, the Early Proterozoic metasedimentary rocks of the Lake Harbour Group, the Abloviak shear zone and the granulite-facies migmatitic complex of the Burwell terrane. The Bouguer gravity profile indicates four distinct zones: (1) in the SW, a low density zone from George River to the east of Keglo Bay; (2) a zone of intermediate density further to the NE from the Lake Harbour Group extending to Abloviak Fiord; (3) a steep, narrow, Bouguer gravity gradient (positive to the N) which is prominent along the Abloviak shear zone; and (4) a high density zone in the extreme NE of the area. The gravity trend on the contoured Bouguer gravity map is NE in zones 1 and 2, where as it is E-W in zones 3 and 4 and could be correlated with a similar trend in the northern part of the Superior Province west of Ungava Bay. Short wavelength anomalies in zone 1 indicate the presence of basin-and-dome structures in the gneissic terrane. Résumé La structure interne de l'orogène Torngat nous est dévoilée à partir de données gravimétriques obtenues dans la partie septentrionale du Québec et du Labrador, le long d'une section orientée SO-NE. Le cheminement situé sur la côte orientale de la baie d'Ungava recoupe le terrene de gneiss archéens du segment de la rivière George, les métasédiments du Groupe de Lake Harbour (Protérozoϊque inférieur), la zone de cisaillement Abloviak et le terrane de Burwell, un complexe migmatitique au facies granulite. Le profil gravimétrique de Bouguer indique quatre zones distinctes : (1) dans le SO, une zone à faible densité à partir de la Rivière George jusqu'à l'est de Keglo Bay; (2) une zone de densité intermédiaire plus loin vers le NE, soit à partir du groupe de Lake Harbour jusqu'au fiord ...