Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

Research Article| December 01, 2003 Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics Jonathan Kim; Jonathan Kim 1Vermont Geological Survey, 103 South Main Street, Waterbury, Vermont 05671, USA Search for other works by this author on: GSW Google Scholar Raymond Coish; Raymond Coish 2Geology Department, Middlebury College, Bicentennial Hall, Middlebury, Vermont 05753, USA Search for other works by this author on: GSW Google Scholar Matthew Evans; Matthew Evans 2Geology Department, Middlebury College, Bicentennial Hall, Middlebury, Vermont 05753, USA Search for other works by this author on: GSW Google Scholar Gregory Dick Gregory Dick 2Geology Department, Middlebury College, Bicentennial Hall, Middlebury, Vermont 05753, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2003) 115 (12): 1552–1569. https://doi.org/10.1130/B25343.1 Article history received: 24 Feb 2003 rev-recd: 03 Jun 2003 accepted: 12 Jun 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Jonathan Kim, Raymond Coish, Matthew Evans, Gregory Dick; Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics. GSA Bulletin 2003;; 115 (12): 1552–1569. doi: https://doi.org/10.1130/B25343.1 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 Metadiabasic intrusions of the Mount Norris Intrusive Suite occur in fault-bounded lithotectonic packages containing Stowe, Moretown, and Cram Hill Formation lithologies in the northern Vermont Rowe-Hawley belt, a proposed Ordovician arc-trench gap above an east-dipping subduction zone. Rocks of the Mount Norris Intrusive Suite are characteristically massive and weakly foliated, have chilled margins, contain xenoliths, and have sharp contacts that both crosscut and are parallel to early structural fabrics in the host metasedimentary rocks. Although the mineral assemblage of the Mount Norris Intrusive Suite is albite + actinolite + epidote + chlorite + calcite + quartz, intergrowths of albite + actinolite are probably pseudomorphs after plagioclase + clinopyroxene. The metadiabases are subalkaline, tholeiitic, hypabyssal basalts with preserved ophitic texture. A backarc-basin tectonic setting for the intrusive suite is suggested by its LREE (light rare earth element) enrichment, negative Nb-Ta anomalies, and Ta/Yb vs. Th/Yb trends. Although no direct isotopic age data are available, the intrusions are broadly Ordovician because their contacts are clearly folded by the earliest Acadian (Silurian–Devonian) folds. Field evidence and geochemical data suggest compelling along-strike correlations with the Coburn Hill Volcanics of northern Vermont and the Bolton Igneous Group of southern Quebec. Isotopic and stratigraphic age constraints for the Bolton Igneous Group bracket these backarc magmas to the 477–458 Ma interval. A tectonic model that begins with east-dipping subduction and progresses to outboard west-dipping subduction after a syncollisional polarity reversal best explains the intrusion of deformed metamorphosed metasedimentary rocks by backarc magmas. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.