Palaeozoic to Early Jurassic history of the northwestern corner of Gondwana,and implications for the evolution of the Iapetus,Rheic and Pacific Oceans |
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| Institution: | 1. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraichers 13, 1205 Geneva, Switzerland;2. Institute of Mineralogy and Geochemistry, University of Lausanne, 1015 Lausanne, Switzerland;3. Instituto Colombiano del Petróleo, Ecopetrol, Bucaramanga, Colombia;1. Department of Earth Sciences and the Environment, University of Geneva, Rue des Maraichers 13, Geneva 1205, Switzerland;2. HRH Geology, 19 Silverburn Place, Aberdeen AB23 8GE, United Kingdom;3. Institut für Geologie und Paläontologie, Corrensstrasse 24, D-48149 Münster, Germany;4. Deptartment of Earth, Ocean and Atmospheric Sciences, The University of British Columbia, Vancouver V6T 1Z4, Canada;5. Institute of Mineralogy and Geochemistry, University of Lausanne, Switzerland;6. Institute of Geosciences, Mineralogy, J. W. Goethe University, Frankfurt 60438, Germany;2. CRU, London, United Kingdom;3. Departamento de Geología, Facultad de Ingeniería en Geología y Petróleos, Escuela Politécnica Nacional, Quito, Ecuador;4. Norway Geological Survey, Trondheim, Norway;5. School of Geosciences, The University of Edinburgh, Edinburgh, Scotland;6. Geological Institute, ETH Zürich, Zürich, Switzerland;1. Instituto de Geociências, Universidade de São Paulo, Rua do Lago 562, CEP 05508-080, São Paulo, SP, Brazil;2. Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional, Carrera 80 # 65-223, Medellín, Colombia;3. Corporación Geológica Ares, Calle 44A # 53-96, Bogotá, Colombia;4. Department of the Environment, Washington State University, Pullman, Washington 99164, USA;1. Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carr. Ensenada-Tijuana 3918, 22860 Ensenada, B.C., Mexico;2. Instituto de Geología, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, 04510 Coyoacán, DF, Mexico;3. Institut für Geowissenschaften, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany;4. Centro de Geociencias, Campus UNAM 3001, 76230 Juriquilla, Querétaro, Mexico;5. Museum für Naturkunde, Leibniz Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany;6. Department of the Environment, Washington State University, Pullman, WA 99164, USA |
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| Abstract: | The Palaeozoic to Mesozoic igneous and metamorphic basement rocks exposed in the Mérida Andes of Venezuela and the Santander Massif of Colombia are generally considered to define allochthonous terranes that accreted to the margin of Gondwana during the Ordovician and the Carboniferous. However, terrane sutures have not been identified and there are no published isotopic data that support the existence of separate crustal domains. A general paucity of geochronological data led to published tectonic reconstructions for the evolution of the northwestern corner of Gondwana that do not account for the magmatic and metamorphic histories of the basement rocks of the Mérida Andes and the Santander Massif. We present new zircon U–Pb (ICP-MS) data from 52 igneous and metamorphic rocks, which we combine with whole rock geochemical and Pb isotopic data to constrain the tectonic history of the Precambrian to Mesozoic basement of the Mérida Andes and the Santander Massif. These data show that the basement rocks of these massifs are autochthonous to Gondwana and share a similar tectono-magmatic history with the Gondwanan margin of Peru, Chile and Argentina, which evolved during the subduction of oceanic lithosphere of the Iapetus Ocean. The oldest Palaeozoic arc magmatism is recorded at ~ 500 Ma, and was followed shortly by Barrovian metamorphism. Peak metamorphic conditions at upper amphibolite facies are recorded by anatexis at ~ 477 Ma and the intrusion of synkinematic granitoids until ~ 472 Ma. Subsequent retrogression resulted from localised back-arc or intra-arc extension at ~ 453 Ma, when volcanic tuffs and interfingered sedimentary rocks were deposited over the amphibolite facies basement. Continental arc magmatism dwindled after ~ 430 Ma and terminated at ~ 415 Ma, coevally with most of the western margin of Gondwana. After Pangaea amalgamation in the Late Carboniferous to Early Permian, a magmatic arc developed on its western margin at ~ 294 Ma as a result of subduction of oceanic crust of the palaeo-Pacific ocean. Intermittent arc magmatism recorded between ~ 294 and ~ 225 Ma was followed by the onset of the Andean subduction cycle at ~ 213 Ma, in an extensional regime. Extension was accompanied by slab roll-back which led to the migration of the arc axis into the Central Cordillera of Colombia in the Early Jurassic. |
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