U-Th-Pb geochronology of the Coast Mountains batholith in north-coastal British Columbia: Constraints on age and tectonic evolution

Abstract

Research Article| September 01, 2009 U-Th-Pb geochronology of the Coast Mountains batholith in north-coastal British Columbia: Constraints on age and tectonic evolution G. Gehrels; G. Gehrels † 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA †E-mail: [e-mail] Search for other works by this author on: GSW Google Scholar M. Rusmore; M. Rusmore 2Department of Geology, Occidental College, Los Angeles, California 90041, USA Search for other works by this author on: GSW Google Scholar G. Woodsworth; G. Woodsworth 3Geological Survey of Canada, Vancouver, British Columbia V6B-5J3, Canada Search for other works by this author on: GSW Google Scholar M. Crawford; M. Crawford 4Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA Search for other works by this author on: GSW Google Scholar C. Andronicos; C. Andronicos 5Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA Search for other works by this author on: GSW Google Scholar L. Hollister; L. Hollister 6Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA Search for other works by this author on: GSW Google Scholar J. Patchett; J. Patchett 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar M. Ducea; M. Ducea 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar R. Butler; R. Butler 7Department of Chemistry and Physics, University of Portland, Portland, Oregon 97203, USA Search for other works by this author on: GSW Google Scholar K. Klepeis; K. Klepeis 8Department of Geology, University of Vermont, Burlington, Vermont 05405, USA Search for other works by this author on: GSW Google Scholar C. Davidson; C. Davidson 9Department of Geology, Carleton College, Northfield, Minnesota 55057, USA Search for other works by this author on: GSW Google Scholar R. Friedman; R. Friedman 10Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada Search for other works by this author on: GSW Google Scholar J. Haggart; J. Haggart 3Geological Survey of Canada, Vancouver, British Columbia V6B-5J3, Canada Search for other works by this author on: GSW Google Scholar B. Mahoney; B. Mahoney 11Department of Geology, University of Wisconsin, Eau Claire, Wisconsin 54702, USA Search for other works by this author on: GSW Google Scholar W. Crawford; W. Crawford 4Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA Search for other works by this author on: GSW Google Scholar D. Pearson; D. Pearson 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar J. Girardi J. Girardi 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2009) 121 (9-10): 1341–1361. https://doi.org/10.1130/B26404.1 Article history received: 08 Jan 2008 rev-recd: 06 Oct 2008 accepted: 30 Oct 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. Gehrels, M. Rusmore, G. Woodsworth, M. Crawford, C. Andronicos, L. Hollister, J. Patchett, M. Ducea, R. Butler, K. Klepeis, C. Davidson, R. Friedman, J. Haggart, B. Mahoney, W. Crawford, D. Pearson, J. Girardi; U-Th-Pb geochronology of the Coast Mountains batholith in north-coastal British Columbia: Constraints on age and tectonic evolution. GSA Bulletin 2009;; 121 (9-10): 1341–1361. doi: https://doi.org/10.1130/B26404.1 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 Previously published and new U-Pb geochronologic analyses provide 313 zircon and 59 titanite ages that constrain the igneous and cooling history of the Coast Mountains batholith in north-coastal British Columbia. First-order findings are as follows: (1) This segment of the batholith consists of three portions: a western magmatic belt (emplaced into the outboard Alexander and Wrangellia terranes) that was active 177–162 Ma, 157–142 Ma, and 118–100 Ma; an eastern belt (emplaced into the inboard Stikine and Yukon-Tanana terranes) that was active ca. 180–110 Ma; and a 100–50 Ma belt that was emplaced across much of the orogen during and following mid-Cretaceous juxtaposition of outboard and inboard terranes.(2) Magmatism migrated eastward from 120 to 80 (or 60) Ma at a rate of 2.0–2.7 km/Ma, a rate similar to that recorded by the Sierra Nevada batholith.(3) Magmatic flux was quite variable through time, with high (>35–50 km3/Ma per km strike length) flux at 160–140 Ma, 120–78 Ma, and 55–48 Ma, and magmatic lulls at 140–120 Ma and 78–55 Ma.(4) High U/Th values record widespread growth (and/or recrystallization) of metamorphic zircon at 88–76 Ma and 62–52 Ma.(5) U-Pb ages of titanite record rapid cooling of axial portions of the batholith at ca. 55–48 Ma in response to east-side-down motion on regional extensional structures.(6) The magmatic history of this portion of the Coast Mountains batholith is consistent with a tectonic model involving formation of a Late Jurassic–earliest Cretaceous magmatic arc along the northern Cordilleran margin; duplication of this arc system in Early Cretaceous time by >800 km (perhaps 1000–1200 km) of sinistral motion (bringing the northern portion outboard of the southern portion); high-flux magmatism prior to and during orthogonal mid-Cretaceous terrane accretion; low-flux magmatism during Late Cretaceous–Paleocene dextral transpressional motion; and high-flux Eocene magmatism during rapid exhumation in a regime of regional crustal extension. 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