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Evidence of multiple sources involved in the genesis of the neoproterozoic itapetim granitic complex,NE Brazil,based on geochemical and isotopic data
Institution:1. Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78712, USA;2. Department of Earth and Environmental Sciences, University of Michigan, 2534 C.C. Little Building, Ann Arbor, MI 48109, USA;1. Institute of Geosciences, University of Campinas, PO Box 6152, 13083-970 Campinas, Sao Paulo, Brazil;2. Institute of Science and Technology, São Paulo State University, Sao Jose dos Campos, Sao Paulo, Brazil;1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China;3. Eighth Geological Brigade of Hebei Geology and Mineral Resources Exploration Bureau, Qinhuangdao 066000, China;4. Tianjin Center, China Geological Survey, Tianjin 300170, China
Abstract:The Itapetim Complex is a multiple facies intrusion of porphyritic monzogranite hosting isolated, or swarms of, dioritic enclaves and cut by late dikes of biotite granodiorite. It is a syn-tectonic intrusion in relation to the D3 regional deformation phase of the Brasiliano Orogeny. The complex has contacts with metagreywackes and gneissic granites associated with the Mesoproterozoic Cariris Velhos event and, to the northwest, with a belt of gneisses of Paleoproterozoic ages. At least two different sources seem to be involved in the evolution of the Itapetim Complex. The diorite source appears to be a depleted mantle that underwent some small degree of mixture with a Paleoproterozoic enriched mafic crust. The monzogranite source is probably metagreywacke, a mixture of enriched crust of Paleoproterozoic age and volcanic rocks related to the Cariris Velhos event. The granodiorites were generated by partial melting of a source compositionally similar to those suggested for the monzogranite. U–Pb in zircon gave a crystallization age of 638±4.9 Ma for the porphyritic monzogranites and associated mafic rocks. The granodiorite dikes represent a late magmatic event, under intermediate fO2 conditions. The dikes, intruded into brittle fractures, are probably related to 570 Ma intrusions within the Pajeú Para??ba Terrane.
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