Episodic arc-ophiolite emplacement and the growth of continental margins: Late accretion in the Northern Irish sector of the Grampian-Taconic orogeny

Abstract

Research Article| November 01, 2012 Episodic arc-ophiolite emplacement and the growth of continental margins: Late accretion in the Northern Irish sector of the Grampian-Taconic orogeny Steven P. Hollis; Steven P. Hollis 1Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, UK †Current address: CSIRO Earth Science and Resource Engineering, 26 Dick Perry Avenue, Kensington, Western Australia, 6151, Australia; e-mail: steven.hollis@csiro.au Search for other works by this author on: GSW Google Scholar Stephen Roberts; Stephen Roberts 1Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, UK Search for other works by this author on: GSW Google Scholar Mark R. Cooper; Mark R. Cooper 2Geological Survey of Northern Ireland, Colby House, Stranmillis Court, Malone Lower, Belfast BT9 5BJ, UK Search for other works by this author on: GSW Google Scholar Garth Earls; Garth Earls 316 Mill Road, Ballygowan, Newtownards, County Down, BT23 6NG, UK Search for other works by this author on: GSW Google Scholar Richard Herrington; Richard Herrington 4Department of Mineralogy, Natural History Museum, London SW7 5BD, UK Search for other works by this author on: GSW Google Scholar Daniel J. Condon; Daniel J. Condon 5Natural Environment Research Council Isotope Geosciences Laboratory, British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK Search for other works by this author on: GSW Google Scholar Matthew J. Cooper; Matthew J. Cooper 1Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, UK Search for other works by this author on: GSW Google Scholar Sandy M. Archibald; Sandy M. Archibald 6Aurum Exploration Services, Unit S/C, Kells Business Park, Kells, County Meath, Ireland Search for other works by this author on: GSW Google Scholar Stephen J. Piercey Stephen J. Piercey 7Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X5, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2012) 124 (11-12): 1702–1723. https://doi.org/10.1130/B30619.1 Article history received: 09 Oct 2011 rev-recd: 03 May 2012 accepted: 18 May 2012 first online: 08 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 Steven P. Hollis, Stephen Roberts, Mark R. Cooper, Garth Earls, Richard Herrington, Daniel J. Condon, Matthew J. Cooper, Sandy M. Archibald, Stephen J. Piercey; Episodic arc-ophiolite emplacement and the growth of continental margins: Late accretion in the Northern Irish sector of the Grampian-Taconic orogeny. GSA Bulletin 2012;; 124 (11-12): 1702–1723. doi: https://doi.org/10.1130/B30619.1 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 In order to understand the progressive growth of continental margins and the evolution of continental crust, we must first understand the formation of allochthonous ophiolitic and island-arc terranes within ancient orogens and the nature of their accretion. During the early Paleozoic closure of the Iapetus Ocean, diverse sets of arc terranes, oceanic tracts, and ribbon-shaped microcontinental blocks were accreted to the passive continental margin of Laurentia during the Grampian-Taconic orogeny. In the northern Appalachians in central Newfoundland, Canada, three distinct phases of arc-ophiolite accretion have been recognized. New field mapping, high-resolution airborne geophysics, whole-rock and Nd-isotope geochemistry, and U-Pb zircon geochronology within the Tyrone Volcanic Group of Northern Ireland have allowed all three episodes to now be correlated into the British and Irish Caledonides. The Tyrone Volcanic Group (ca. 475–469 Ma) is characterized by mafic to intermediate lavas, tuffs, rhyolite, banded chert, ferruginous jasperoid, and argillaceous sedimentary rocks cut by numerous high-level intrusive rocks. Geochemical signatures are consistent with formation within an evolving peri-Laurentian island-arc/backarc, which underwent several episodes of intra-arc rifting prior to its accretion at ca. 470 Ma to an outboard peri-Laurentian microcontinental block. Outriding microcontinental blocks played a fundamental role within the orogen, explaining the range of ages for Iapetan ophiolites and the timing of their accretion, as well as discrepancies between the timing of ophiolite emplacement and the termination of the Laurentian Cambrian–Ordovician shelf sequences. Accretion of the Tyrone arc and its associated suprasubduction-zone ophiolite represents the third stage of arc-ophiolite emplacement to the Laurentian margin during the Grampian-Taconic orogeny in the British and Irish Caledonides. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.