U–Pb and Sm–Nd geochronology of amphibolites from the Curaçá Belt, São Francisco Craton, Brazil: Tectonic implications |
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Authors: | Luiz Jos Homem D'el-Rey Silva, Elton Luiz Dantas, Jo o Batista Guimar es Teixeira, Jorge Henrique Laux,Maria da Gl ria da Silva |
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Affiliation: | aUniversidade de Brasília — Instituto de Geociências bLaboratório de Geocronologia, Universidade de Brasília, Campus Darcy Ribeiro, Asa Norte, 70.910-900, Brasília — DF, Brazil cGrupo de Metalogênese, Centro de Pesquisa em Geofísica e Geologia, Universidade Federal da Bahia, Campus Universitário de Ondina, Sala 201-C, Salvador, 40170-290, Bahia, Brazil dServiço Geológico do Brasil (CPRM) - Av. Pasteur 404, Urca, 22290-240 Rio de Janeiro — RJ, Brazil |
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Abstract: | The Curaçá terrane is part of the Itabuna–Salvador–Curaçá (I–S–C) Paleoproterozoic orogen in the São Francisco craton, northeastern Brazil, and comprises supracrustal rocks, gneisses of their probable basement, amphibolites, and mafic-ultramafic Cu-bearing bodies (including the Caraíba Cu-Mine), all affected by D1-D3 deformation events associated to M1-M3 metamorphism under high-T granulite and amphibolite facies, and assisted by G1-G3 tonalitic-granodioritic-granitic intrusions. U–Pb and Sm–Nd Thermal Ionization Mass Spectrometry (TIMS) isotopic data from amphibolite, tonalite, and granite, sampled in a well-known outcrop, indicate partial reset and heterogeneous modification of the original isotopic systems, attributable to deformation and metamorphism. The ages obtained from these systems agree with each other, and also with other previously published U–Pb data, and imply that 2.6 Ga is the crystallization age of the protolith of the amphibolite. Together with key structural relationships, they also indicate a 2.08–2.05 Ga interval for M3 metamorphism, and make even a less precise age (2.2–2.3 Ga) acceptable, as it suggests contamination in the amphibolite with material in a syn-D2 tonalite crystallized 2248 ± 36 Ma ago. The new data demonstrate the existence of Neoarchean fragments of both oceanic and continental crusts and constrain the Archean-Paleoproterozoic development of the Curaçá belt, the I–S–C orogen, and the São Francisco craton. |
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Keywords: | U–Pb and Sm–Nd isotopic data Curaçá terrane São Francisco craton Archean to Paleoproterozoic tectonics Caraíba Mine |
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