The Abloviak shear zone and the NW Torngat Orogen, eastern Ungava Bay,Québec.

• Main Authors: Goulet, Normand, Ciesielski, André
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Association of Canada 1990
• Subjects: Lake Harbour; Ungava Bay; Baie d'Ungava
• Online Access: https://journals.lib.unb.ca/index.php/GC/article/view/3702

The NW-trending Torngat Orogen in eastern Ungava Bay, which contains Early Proterozoic sedimentary rocks and Archean orthogneiss, is subdivided into the Burwell terrane, Tasiuyak gneiss, Lake Harbour Group and the George River segment. The Burwell terrane, a granulite-facies migmatitic complex, grades to the southwest into the Tasiuyak gneiss composed of plagioclase-garnet-quartz-sillimanite and graphite. Further to the southwest, the Tasiuyak gneiss passes gradationally into amphibolite-facies pelitic gneiss, quartzite and marble of the Lake Harbour Group, which is associated with granodioritic Archean orthogneiss of the George River segment. The 15 km wide Abloviak shear zone, a high strain zone within the eastern Torngat Orogen, overprints and subvertically transposes the Tasiuyak gneiss, part of the Lake Harbour Group and its Archean basement. D1 deformation is interpreted to have resulted in development of early foliation, and west- to southwest-verging thrusts that interleaved Lake Harbour Group rocks and George River segment gneiss. D2 was a transpressional deformation event responsible for refolding in the Lake Harbour Group and development of mylonitic fabrics in the Abloviak shear zone. The latter comprises medium- to highly-strained rocks (mylonites) formed in a major transcurrent sinistral shear environment. The Lake Harbour Group is deformed into km-scale NNW-trending dome-and-basin structures, involving Archean basement, that were vertically transposed in a northwest ward direction toward the Abloviak shear zone. Résumé L'orogène Torngat est orientée NO à l'est de la baie d'Ungava et contient des roches sédimentaires protérozoïques et des orthogneiss archéens. Le complexe de Burwell, un terrane migmatitique au faciès granulite passe graduellement vers le SO dans les gneiss de Tasiuyak composés de plagloclase-grenat-quartz-sillimanite et graphite. Au SO, les gneiss de Tasiuyak sont intercalés avec des métasédiments du groupe de Lake Harbour. Plus à l'ouest, le groupe de Lake Harbour formé de ...