Geochronology of granulites from the south Itabuna-Salvador-Curaçá Block,São Francisco Craton (Brazil): Nd isotopes and U–Pb zircon ages |
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| Authors: | Jean-Jacques Peucat Johildo Salomão Figueiredo Barbosa Ivana Conceição de Araújo Pinho Jean-Louis Paquette Hervé Martin C Mark Fanning Angela Beatriz de Menezes Leal Simone Cruz |
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| Institution: | 1. National Taiwan Normal University, Department of Earth Science, 88 Tingzhou Road Section 4, Taipei 11677, Taiwan;2. School of Studies in Geology and Water Resource Management, Pt. Ravishankar Shukla University, Raipur 492010, Chhattisgarh, India;3. University of Western Australia, School of Earth Sciences, 35 Stirling Highway, 6009, Australia;4. National Institute of Technology, Department of Applied Geology, Raipur, Chhattisgarh 492010, India;5. Govt. V.Y.T.P.G. Autonomous College, Department of Geology, Durg, Chhattisgargh 491001, India;1. Department of Geosciences, The University of Arizona, Tucson, AZ, USA;2. School of the Environment, Washington State University, Pullman, WA, USA;3. Earth, Atmospheric and Planetary Sciences Department, Massachusetts Institute of Technology, Cambridge, MA, USA;1. CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;3. Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;4. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Science, Beijing 100101, China;5. University of Chinese Academy of Sciences, Beijing 100094, China;6. SOA Key Laboratory of Submarine Geociences Second Institute of Oceanography State Ocean Administration, Hangzhou 310012, China |
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| Abstract: | This work provides five new U–Pb zircon dating and the corresponding Nd isotope data for felsic granulites from the south Itabuna-Salvador-Curaçá Block (ISCB), in the São Francisco Craton, Brazil. Three major sets of felsic granulites can be recognised. The oldest set is tonalitic in composition and of TTG affinity. It is Archaean in age with magmatic zircon cores dated at 2675 ± 11 Ma by LA-ICPMS and up to ca 2.7–2.9 Ga by SHRIMP on an other sample. It exhibits epsilon Nd values between ?8 and ?11 at 2.1 Ga. This Nd signature is similar to that of granulites found in the western Archaean Jequié Block. Cartographically, this set of Archaean terrains represents at least 50% of the granulites in the studied area. The second set corresponds to a Palaeoproterozoic calc-alkaline tonalitic suite with zircon ages from 2019 ± 19 Ma to 2191 ± 10 Ma and epsilon Nd values between ?3 and ?4 at 2.1 Ga, corresponding partially to a newly formed crust. The third set of granulites is also Palaeoproterozoic. It is shoshonitic to monzonitic in composition and synchronous with the high grade metamorphism dated by metamorphic zircons at 2086 ± 7 Ma (average of five samples). The Nd isotope signature for this alkaline set is similar to that of the Palaeoproterozoic calc-alkaline one. Nd isotopes appear to be a very efficient tool to distinguish Archaean from Palaeoproterozoic felsic protoliths in granulitic suites of the Itabuna-Salvador-Curaçá Block (ISCB). Finally, the southern part of the ISCB is composed of a mixture of Archaean and Palaeoproterozoic protoliths, in similar amounts, suggesting that it was probably an active margin between 2.1 and 2.2 Ga located on the eastern border of the Archaean Jequié Block. A major crustal thickening process occurred at ca 2.09 Ga in the ISCB and seems significantly younger towards the west, in the Jequié granulites, where an average of 2056 ± 9 Ma is determined for the high grade event. |
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