U–Pb zircon geochronology of the Ediacaran volcano-sedimentary succession of the NE Saghro inlier (Anti-Atlas,Morocco): Chronostratigraphic correlation on the northwestern margin of Gondwana |
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| Institution: | 1. Department of Geology, Faculty of Sciences-Semlalia, Cadi Ayyad University, P.O. Box 2390, Marrakech, Morocco;2. LGE. Department of Geology, ENS, Cadi Ayyad University, BP S2400, Marrakech, Morocco;3. Em. Pr. Université de Paris-Sud, 10 rue des Jeûneurs, 75002, Paris, France;4. Department of Mineralogy and Petrology, University of Granada, Campus Fuentenueva, 18002, Granada, Spain;5. UMR Geoazur, 250 rue A. Einstein, Université de Nice - Sophia-Antipolis, 06560, Valbonne, France;6. Direction de la Géologie, Ministère de l''Energie et des Mines, B.P. 6208, Rabat Instituts, Haut Agdal, Rabat, Morocco;7. Laboratoire Géosciences, Université Hassan II-Casablanca, BP 5366, Maârif, Casablanca, Morocco;8. Marine Science, Safety and Environmental Protection Department, Massachusetts Maritime Academy, Buzzards Bay, MA, USA, 02532;1. Department of Geology, Faculty of Sciences-Semlalia, Cadi Ayyad University, Prince Moulay Abdellah Boulevard, P.O. Box 2390, 40 000, Marrakech, Morocco;2. LAGAGE Laboratory, Department of Geology, Faculty of Sciences, Ibn Zohr University, P.O. Box 28/S, 80 000, Agadir, Morocco;3. Université de Lorraine, CNRS, CRPG, F-54000, Nancy, France;4. Ottawa-Carleton Geoscience Centre, Department of Earth Sciences Carleton University, 1125 Colonel By Drive Ottawa, Ontario, K1S5B6, Canada;5. LGCA, Département de Géologie, Université Hassan II de Casablanca, Morocco;6. Managem Group, Twin Center, 20100, Casablanca, Morocco;1. Isotope Geochemistry/Geochronology Lab, Department of Geological Sciences, University of North Carolina – Chapel Hill, Chapel Hill, NC 27516, USA;2. Geography and Geology Department, University of Wisconsin – Stevens Point, Stevens Point, WI 54481, USA;3. Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, USA;4. Department of Geology, Faculty of Sciences Semlalia, Cadi Ayyad University, Boulevard Prince My Abdellah, B.P. 2390 MAROC, Marrakech 40005, Morocco;5. Reminex Mining, Marrakech, Morocco;1. BRGM, BP 6009, 45060 Orléans Cédex, France;2. Geology Department, Faculty of Sciences-Semlalia, Cadi Ayyad University, PO Box 2390, 40000 Marrakech, Morocco;3. Laboratoire EDYTEM, Université de Savoie, CNRS, Campus Scientifique, 73376 Le Bourget du Lac Cedex, France;4. EGID, Université de Bordeaux 3, 33607 Pessac Cedex, France;5. GEODE Terre et Patrimoine, B.P. 7004, 40014 Marrakech, Morocco;6. Universidade de Lisboa, Faculdade de Ciências, Departamento de Geologia, Centro de Geologia, Portugal;1. Laboratory of Geodynamics of Old Chains, Faculty of Sciences Ben M''Sik, University Hassan II of Casablanca, B.P.7955, Casablanca, Morocco;2. Laboratory of Geo-biodiversity and Natural Patrimony, Scientific Institut, Geophysics, Natural, Patrimony and Green Chemistry Research Center (GEOPAC), Mohammed V University in Rabat, Morocco;3. Department of Geodynamics, Faculty of Sciences, University of Granada, Granada, Spain;4. EDYTEM, Université Savoie Mont Blanc, CNRS-UMR 5204, Campus Scientifique, 73376, Le Bourget du Lac Cédex, France |
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| Abstract: | We report a new regional correlation for the Ediacaran succession in the Anti-Atlas belt on the northwestern margin of Gondwana, based on U-Pb LA-ICP-MS zircon geochronology of volcanic rocks in the NE edge of the Saghro inlier. The thick volcano-sedimentary succession comprises a diverse suite of rhyolitic-ignimbrite, basaltic to andesitic lava fields, rhyolitic lava, mafic hydroclastic complex, fallout and surge deposits, pyroclastic dyke, interbedded clastic sediment and subvolcanic bodies.Ten volcanic rocks yield crystallization ages ranging from 573 to 547 Ma, consistent with a lower and upper Ouarzazate Supergroup affinity respectively. Inherited zircon ages range from 623 Ma to 600 Ma, analogous to zircon peaks in the older volcano-sedimentary rocks of the Bou Salda, and Saghro groups in the Anti-Atlas, suggesting the continuity of the Saghro Group beneath the Ouarzazate Supergroup at the NE edge of the Saghro inlier.Rocks with a lower Ouarzazate Supergroup affinity include lithic-poor ignimbrites which yield ages of 573.6 ± 1.9 Ma, 571.8 ± 4.2 Ma, 571.3 ± 2.6 Ma, and 567.4 ± 2.9 Ma, two fallout deposits which yield ages of 563.5 ± 2.1 Ma and 569.2 ± 1.9 Ma, a surge deposit dated at 571.6 ± 2.8 Ma and a rhyolite lava dated at 562.5 ± 3.1 Ma. Two lithic-poor ignimbrites from the upper Ouarzazate Supergroup are dated at 557.3 ± 2.6 Ma and 547.9 ± 3.1 Ma.Volcanic activity at the NE edge of the Saghro inlier is related to West African Cadomian orogenic (WACadomian) activity between 620 and 560 Ma. During this period the Saghro and Bou Salda groups were deposited, followed by the lower Ouarzazate Supergroup. Later extension along the Gondwanan margin took place close to Ediacaran – Cambrian boundary, contemporaneous with upper Ouarzazate Supergroup deposition. |
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