The missing Rheic Ocean magmatic arcs: Provenance analysis of Late Paleozoic sedimentary clastic rocks of SW Iberia |
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| Institution: | 1. British Geological Survey, Columbus House, Cardiff, CF15 7NE, UK;2. Department of Earth Sciences, The University of Western Ontario, London, Ontario N6A 5B7, Canada;3. Department of Earth and Environmental Science, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada;4. National Museum of Wales, Cathays Park, Cardiff, CF10 3NP, UK;5. NERC Isotope Geoscience Laboratory, Keyworth, Nottingham, NG12 5GG, UK;1. Department of Geodynamics, University of Granada, Granada, Spain;2. School of Geosciences, University of Edinburgh, Edinburgh, UK;3. John de Laeter Centre, Curtin University, Bentley, Australia;4. School of Earth and Planetary Science, John the Laeter Centre, Curtin University, Perth, Australia;5. Faculté Pluridisciplinaire de Nador et Laboratoire des Géosciences Appliquées, Faculté des Sciences, Université Mohammed I, Oujda, Morocco;6. Geo-Biodiversity and Natural Patrimony Laboratory (GeoBio), Scientific Institute, Geophysics, Natural Patrimony Research Center (GEOPAC) Mohammed V University, Rabat, Morocco;7. Faculté des Sciences Ben M''Sik, Université Hassan II, Casablanca, Morocco;1. Dipartimento di Geoscienze, Università di Padova, 35131 Padova, Italy;2. IGG-CNR, 35131, Padova, Italy;3. Section of Earth and Environmental Science, Université de Genève, Genève 1205, Switzerland;4. Geology Department, Faculty of Sciences Semlalia, Cadi Ayyad University, Prince Moulay Abdellah Boulevard, P.O. Box 2390, Marrakech, Morocco;5. Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal;6. Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;7. Australian National University, Research School of Earth Sciences, 142 Mills Rd, Acton, ACT 2601, Australia;8. Hanse-Wissenschaftskolleg (HWK), Lehmkuhlenbusch 4, 27753 Delmenhorst, Germany;9. Institute of Geological Sciences, Polish Academy of Sciences, Warsaw, Poland;10. Moroccan Association of Geosciences, Rabat, Morocco;11. Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland;12. 9 Dexters Lane, Grand Manan, New Brunswick, Canada E5G 3A6 |
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| Abstract: | Early Carboniferous turbiditic sedimentary rocks in synorogenic basins located on both sides of the Rheic suture in SW Iberia were studied for provenance analysis. An enigmatic feature of this suture, which resulted from closure of the Rheic Ocean with the amalgamation of Pangea in the Late Carboniferous, is that there are no recognizable mid- to Late Devonian subduction-related magmatic rocks, which should have been generated during the process of subduction, on either side of it. U–Pb LA–ICP-MS geochronology of detrital zircons from Early Carboniferous turbidites in the vicinity of the Rheic suture in SW Iberia, where it separates the Ossa–Morena Zone (with Gondwana continental basement) to the north from the South Portuguese Zone (with unknown/Meguma? continental basement) to the south, reveals the abundance of mid- to Late Devonian (51–81%) and Early Carboniferous (13–25%) ages. The Cabrela and Mértola turbidites of the Ossa–Morena and South Portuguese zones, respectively, are largely devoid of older zircons, differing from the age spectra of detrital zircons in the oldest (Late Devonian) strata in the underlying South Portuguese Zone, which contain abundant Cambrian and Neoproterozoic ages. Mid- to Late Devonian zircons in the Cabrela Formation (age cluster at c. 391 Ma, Eifelian–Givetian transition) and Mértola Formation (age clusters at c. 369 Ma and at c. 387 Ma, Famennian and Givetian respectively) are attributable to a source terrane made up of magmatic rocks with a simple geological history lacking both multiple tectonic events and older continental basement. The terrane capable of sourcing sediments dispersed on both sides of the suture is interpreted to have been completely removed by erosion in SW Iberia. Given that closure of the Rheic Ocean required subduction of its oceanic lithosphere and the absence of significant arc magmatism on either side of the Rheic suture, we suggest: 1) the source of the zircons in the SW Iberia basins was a short-lived Rheic ocean magmatic arc, and 2) given the lack of older zircons in the SW Iberia basins, this short-lived arc was probably developed in an intra-oceanic environment. |
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