The record of the Late Palaeozoic active margin of the Palaeotethys in NE Iran: Constraints on the Cimmerian orogeny |
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| Affiliation: | 1. Dipartimento di Scienze Geologiche e Geotecnologie, Università degli Studi di Milano Bicocca, Piazza della Scienza 4, 20126 Milano, Italy;2. Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli 34, 20133 Milano, Italy;3. CNRS “Géosystèmes”, Université de Lille 1 UMR 8217, 59655 Villeneuve d''Ascq cedex, France;4. Geological Survey of Iran, Azadi Square, Meraj Avenue, 13185-1494 Tehran, Iran;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. CAS Center for Excellence in Tibetan Plateau Earth Sciences, China;4. Department of Geology, Payame Noor University, Iran;1. Geology Department, Faculty of Basic Sciences, Tarbiat Modares University, Tehran, Iran;2. Mining Departments, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran;3. AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Al. Mickiewicza 30, 30-059 Krakow, Poland;4. Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan;5. Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan;6. Department of Applied Chemistry for Environment, School of Science and Technology, Kwansei Gakuin University, Sanda 669-1337, Japan;7. Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan;1. Department of Earth and Environmental Sciences, Kumamoto University, Kumamoto 860-8555, Japan;2. Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan;3. Department of Earth and Sea Sciences, University of Palermo, Via Archirafi 22, 90123 Palermo, Italy;4. Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padova, Italy;5. IGG-CNR, Via Gradenigo 6, 35131 Padova, Italy;1. Sorbonne Universités, UPMC Univ Paris06, ISTEP, Institut des Sciences de la Terre de Paris, France;2. CNRS, Centre National de la Recherche Scientifique, UMR 7193, Paris, France;3. Institut Universitaire de France, IUF, Paris, France;4. Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier, Centre National de la Recherche Scientifique (CNRS), UMR 5275, F-38041 Grenoble, France;5. Department of Geosciences, National Taiwan University, Taipei, 106, Taiwan;6. Department of Geology, University of Birjand, Birjand, Iran;7. Géosciences Montpellier, UMR 5243, 349095 Montpellier, France |
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| Abstract: | The Cimmerian orogen resulted from the collision and accretion of several Perigondwanan blocks to the southern margin of Eurasia between the Late Triassic and Early Jurassic, following the closure of the Palaeotethys ocean. Remnants of this orogen discontinuously crop out in N (Alborz range) and NE Iran (Mashhad–Fariman area) below the syn- to post-collisional clastic successions of the Shemshak Group (Upper Triassic–Middle Jurassic) and the Kashaf Rud Formation (Bajocian). In NE Iran rock associations exposed in the Binalood Mountains, Fariman and Darreh Anjir areas include mafic–ultramafic intrusive rocks, basalts, silicoclastic turbidites and minor limestones, which have been interpreted in the past as ophiolitic remnants of the Palaeotethys ocean. Original stratigraphic, structural, geochemical and geochronological data, described in this paper, suggest a different interpretation. The volcano-sedimentary units of Fariman and Darreh Anjir complexes where deposited during Permian in a subsiding basin were siliciclastic turbidites, derived from the erosion of a magmatic arc and its basement, interfinger with carbonates and basaltic lava flows with both transitional and calc-alkaline affinity. The coexistence of magmatic rocks with different geochemical signature and the sedimentary evolution of the basin can be related to a supra-subduction setting, possibly represented by a fault-controlled intra-arc basin. The Fariman and the Darreh Anjir complexes are thus interpreted as remnants of a magmatic arc and related basins developed at the southern Eurasia margin, on top of the north-directed Palaeotethys subduction zone long before the collision of Iran with Eurasia. They were later involved in the Cimmerian collision during the Triassic. New radiometric ages obtained on I-type post-collisional granitoids postdating the collision-related deformational structures suggest that the suture zone closed before mid-Norian times. Deformation propagated later northward into the Turan domain involving the Triassic successions of the Aghdarband region. |
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