Acadian metamorphism in the Dunnage zone of southern Québec, northern Appalachians: 40Ar/39Ar evidence for collision diachronism

Abstract

Research Article| January 01, 2000 Acadian metamorphism in the Dunnage zone of southern Québec, northern Appalachians: 40Ar/39Ar evidence for collision diachronism Alain Tremblay; Alain Tremblay 1Centre Géoscientifique de Québec, INRS-Géoressources, 2535 Boulevard Laurier, Ste-Foy, Québec G1V 4C7, Canada Search for other works by this author on: GSW Google Scholar Gilles Ruffet; Gilles Ruffet 2UMR-Géosciences Azur, Centre National de Recherche Scientifique, Université de Nice-Sophia Antipolis, 06108 Nice Cedex 02, France Search for other works by this author on: GSW Google Scholar Sébastien Castonguay Sébastien Castonguay 1Centre Géoscientifique de Québec, INRS-Géoressources, 2535 Boulevard Laurier, Ste-Foy, Québec G1V 4C7, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2000) 112 (1): 136–146. https://doi.org/10.1130/0016-7606(2000)112<136:AMITDZ>2.0.CO;2 Article history received: 17 Aug 1998 rev-recd: 02 Mar 1999 accepted: 12 Mar 1999 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Alain Tremblay, Gilles Ruffet, Sébastien Castonguay; Acadian metamorphism in the Dunnage zone of southern Québec, northern Appalachians: 40Ar/39Ar evidence for collision diachronism. GSA Bulletin 2000;; 112 (1): 136–146. doi: https://doi.org/10.1130/0016-7606(2000)112<136:AMITDZ>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract In New England, the Acadian orogen is divided into Western and Eastern metamorphic belts on the basis of contrasting pressure-temperature (P-T) paths, peak metamorphism conditions, and ages. Along-strike correlations of structures indicate that rock units affected by Devonian metamorphism and deformation in southern Québec belong to the Western Acadian belt, and share the same tectonic evolution as in New England. Muscovite 40Ar/39Ar ages obtained from greenschist-grade, Ordovician volcanic and plutonic rocks of the Ascot Complex in southern Québec indicate that Acadian metamorphism and deformation peaked ca. 380–375 Ma. Ordovician muscovite ages of ca. 462 Ma are locally well preserved in the granitic intrusion of the Ascot Complex, and provide constraints on the timing of island-arc plutonism in the Dunnage zone of southern Québec. Ordovician 40Ar/39Ar age spectra do not show important losses of radiogenic argon, indicating that Acadian metamorphism has been low grade, with temperatures below the Ar isotopic closure temperature proposed for muscovite. Acadian peak metamorphism is significantly younger, and P-T conditions of regional deformation have been lower in southern Québec than in amphibolite-grade rocks of the Western Acadian belt of New England. In the northern Appalachians, Acadian metamorphism and deformation are attributed to Devonian age crustal overthickening related to plate convergence. The comparison of Devonian tectonic fabrics in New England and southern Québec suggests that progression in the timing and P-T conditions of Acadian peak metamorphism in both areas are the result of the irregular geometry of the collision zone and of the northward migration of metamorphic and structural fronts along the orogen. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.