Tectonometamorphic evolution of the southern Quebec Appalachians: 40Ar/39Ar evidence for Middle Ordovician crustal thickening and Silurian–Early Devonian exhumation of the internal Humber zone

Abstract

Research Article| January 01, 2001 Tectonometamorphic evolution of the southern Quebec Appalachians: 40Ar/39Ar evidence for Middle Ordovician crustal thickening and Silurian–Early Devonian exhumation of the internal Humber zone Sébastien Castonguay; Sébastien Castonguay 1Geological Survey of Canada, Centre Géoscientifique de Québec, C.P. 7500, Sainte-Foy, Quebec G1V 4C7, Canada Search for other works by this author on: GSW Google Scholar Gilles Ruffet; Gilles Ruffet 1Geological Survey of Canada, Centre Géoscientifique de Québec, C.P. 7500, Sainte-Foy, Quebec G1V 4C7, Canada Search for other works by this author on: GSW Google Scholar Alain Tremblay; Alain Tremblay 1Geological Survey of Canada, Centre Géoscientifique de Québec, C.P. 7500, Sainte-Foy, Quebec G1V 4C7, Canada Search for other works by this author on: GSW Google Scholar Gilbert Féraud Gilbert Féraud 4UMR-Géosciences Azur, Centre National de la Recherche Scientifique–Université de Nice–Sophia Antipolis, 06108 Nice Cedex 02, France Search for other works by this author on: GSW Google Scholar GSA Bulletin (2001) 113 (1): 144–160. https://doi.org/10.1130/0016-7606(2001)113<0144:TEOTSQ>2.0.CO;2 Article history received: 08 Jan 1999 rev-recd: 09 Feb 2000 accepted: 10 Feb 2000 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Sébastien Castonguay, Gilles Ruffet, Alain Tremblay, Gilbert Féraud; Tectonometamorphic evolution of the southern Quebec Appalachians: 40Ar/39Ar evidence for Middle Ordovician crustal thickening and Silurian–Early Devonian exhumation of the internal Humber zone. GSA Bulletin 2001;; 113 (1): 144–160. doi: https://doi.org/10.1130/0016-7606(2001)113<0144:TEOTSQ>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 Published age data from the Humber zone of the southern Quebec Appalachians indicate that deformation and metamorphism occurred during Middle to Late Ordovician time. This paper presents the results of a regional-scale geochronological study of 70 amphibole and mica single grains by the 40Ar/39Ar laser step-heating method, which brings forward a more complete Middle Ordovician–Early Devonian tectonometamorphic evolution of the Quebec Appalachian Humber zone. Biotites have plateau ages varying between 420 and 411 Ma. Amphiboles are often compositionally rimmed and/or contain biotite inclusions. Their age spectra are generally disturbed, but may suggest the occurrence of two distinct events: Silurian (429–424 Ma) and Middle Ordovician (462–460 Ma). Two main groups of muscovite ages have been obtained: Middle Ordovician (469–461 Ma) and Silurian–Early Devonian (431–411 Ma), but Middle to Late Devonian (387–376 Ma) ages are also locally present. Middle Ordovician ages are interpreted to record crustal thickening by nappe emplacement during regional Taconian metamorphism. Silurian–Early Devonian ages are attributed to consequences of backthrusting and normal faulting. A statistical analysis of Silurian–Early Devonian muscovite age spectra reveals an irregular decrease in weighted apparent age maxima across the internal Humber zone. This age-decreasing trend is interpreted to result from the temporal (ca. 431–411 Ma) and possibly spatial (northwest to southeast) progression of deformation, recrystallization, and fluid circulation during tectonic exhumation of the internal Humber zone in southern Quebec. Tectonic models for the Northern Appalachian internal Humber zone should take into account the strong body of evidence for Silurian–Early Devonian hinterland-directed and extensional deformation as documented in southern Quebec. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.