Geochemical constraints on the origin of the Annieopsquotch ophiolite belt, Newfoundland Appalachians

Abstract

Research Article| November 01, 2005 Geochemical constraints on the origin of the Annieopsquotch ophiolite belt, Newfoundland Appalachians C. Johan Lissenberg; C. Johan Lissenberg 1Department of Earth Sciences, University of Ottawa and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada Search for other works by this author on: GSW Google Scholar Cees R. van Staal; Cees R. van Staal 2Geological Survey of Canada, Natural Resources Canada, 615 Booth Street, Ottawa, Ontario K1A 0E8, Canada and Department of Earth Sciences, University of Ottawa and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada Search for other works by this author on: GSW Google Scholar Jean H. Bédard; Jean H. Bédard 3Geological Survey of Canada, Natural Resources Canada, 880 Chemin St.-Foy, Quebec, Quebec G1S 2L2, Canada Search for other works by this author on: GSW Google Scholar Alexandre Zagorevski Alexandre Zagorevski 4Department of Earth Sciences, University of Ottawa and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information C. Johan Lissenberg 1Department of Earth Sciences, University of Ottawa and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada Cees R. van Staal 2Geological Survey of Canada, Natural Resources Canada, 615 Booth Street, Ottawa, Ontario K1A 0E8, Canada and Department of Earth Sciences, University of Ottawa and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada Jean H. Bédard 3Geological Survey of Canada, Natural Resources Canada, 880 Chemin St.-Foy, Quebec, Quebec G1S 2L2, Canada Alexandre Zagorevski 4Department of Earth Sciences, University of Ottawa and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada Publisher: Geological Society of America Received: 24 Sep 2004 Revision Received: 26 May 2005 Accepted: 31 May 2005 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2005) 117 (11-12): 1413–1426. https://doi.org/10.1130/B25731.1 Article history Received: 24 Sep 2004 Revision Received: 26 May 2005 Accepted: 31 May 2005 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 C. Johan Lissenberg, Cees R. van Staal, Jean H. Bédard, Alexandre Zagorevski; Geochemical constraints on the origin of the Annieopsquotch ophiolite belt, Newfoundland Appalachians. GSA Bulletin 2005;; 117 (11-12): 1413–1426. doi: https://doi.org/10.1130/B25731.1 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 The Early Ordovician Annieopsquotch ophiolite belt occurs immediately west of the main Iapetus suture zone, and imposes important constraints on the tectonic processes associated with closure of the peri-Laurentian portion of Iapetus. The Annieopsquotch ophiolite, the most prominent ophiolite within the Annieopsquotch ophiolite belt, exposes a 5.5-km-thick section of gabbros, sheeted dikes, and pillow basalts, in which three magmatic episodes have been recognized based on field and geochemical data. The first phase is composed of layered troctolites, which are preserved as enclaves within the gabbro zone. Trace element modeling suggests the troctolites crystallized from boninitic melts. The troctolite substrate was intruded by the dominant, second, tholeiitic magmatic phase, which formed a gabbro-sheeted dike-basalt sequence. All tholeiites have suprasubduction zone chemical characteristics, but the suprasubduction zone signature decreases toward the top of the basalt sequence. The third magmatic episode is composed of primitive dikes, which are interpreted as off-axis intrusions. Other ophiolites within the Annieopsquotch ophiolite belt have comparable geochemical signatures, suggesting they may have constituted a single piece of oceanic lithosphere. Based on geochemical and regional tectonic constraints, the Annieopsquotch ophiolite belt is interpreted to have formed during initiation of west-directed subduction. Fast rollback of the subducting slab would have induced volatile-fluxed decompression melting of previously depleted mantle, yielding boninitic melts. The suprasubduction zone tholeiite sequence would have formed from ascending fertile mantle fluxed with sub-duction-related fluids as rollback continued. This suggests that the Annieopsquotch ophiolite belt does not represent the remnants of normal oceanic crust or backarc basin crust, as previously thought. Our model constrains the initiation and early evolution of a west-dipping peri-Laurentian subduction zone that was responsible for formation of several arc-backarc complexes currently preserved in the Annieopsquotch Accretionary Tract. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.