U-Pb geochronology of the Lagoa Real uranium district, Brazil : implications for the age of the uranium mineralization.
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2015
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The Lagoa Real uranium district in Bahia, northeastern Brazil, is the most important uranium province in the country and presently produces this metal in an open-pit mine operated by Indústrias Nucleares do Brasil. Uranium-rich zones are associated with plagioclase (dominantly albite ± oligoclase) -rich rocks, albitites and metasomatized granitic-gneisses, distributed along NNW/SSE striking shear zones. We have used the ID-TIMS U-Pb method to date zircon and titanite grains from the São Timóteo granitoid, and albite-rich rocks from the Lagoa Real district in order to assess the age of granite emplacement, deformation/metamorphism and uranium mineralization. The isotopic data support the following sequence of
events (i) 1746 ± 5 Ma - emplacement of the São Timóteo granitoid (U-Pb zircon age) in an extensional setting, coeval with the beginning of the sedimentation of the Espinhaço Supergroup; (ii) 956 ± 59 Ma hydrothermal alteration of the São Timóteo granitoid and emplacement of the uranium mineralization (U-Pb titanite age on an albite-rich sample); (iii) 480 Ma metamorphism, remobilization and Pb loss (U-Pb titanite age for the gneiss sample), during the nucleation of shear zones related to the collision between the São Francisco-Congo and Amazonia paleoplates. The 956 ± 59-Ma mineralization age is apparently associated with the evolution of the Macaúbas-Santo Onofre rift. This age bracket may bear an important exploration implication, and should be included in the diverse age scenario of uranium deposits worldwide.
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Lagoa Real uranium deposit, Metasomatic alteration, Metallogenetic implications
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LOBATO, L. M. et al. U-Pb geochronology of the Lagoa Real uranium district, Brazil: Implications for the age of the uranium mineralization. Journal of South American Earth Sciences, v. 58, p. 129-140, 2015. Disponível em: <http://www.sciencedirect.com/science/article/pii/S0895981114001709>. Acesso em: 11 de set. 2015.