UePb geochronology of the Lagoa Real uranium district, Brazil: Implications for the age of the uranium mineralization Lydia Maria Lobato a, * ,M  arcio Martins Pimentel b , Simone C.P. Cruz c , Nuno Machado d, 1 , Carlos Maurício Noce a, 1 , Fernando Flecha Alkmim e a Instituto de Geoci^ encias-CPMTC, Universidade Federal de Minas Gerais, Av. Ant^ onio Carlos 6627, Campus Pampulha, 30130-009 Belo Horizonte, Minas Gerais, Brazil b Instituto de Geoci^ encias, Universidade de Brasília, Campus Darcy Ribeiro ICC, Ala Central, 70910-900, Brasília, Distrito Federal, Brazil c Instituto de Geoci^ encias, Universidade Federal da Bahia, Av. Caetano Moura, S/N, Federaç~ ao, 40000-000 Salvador, Bahia, Brazil d Centre de Recherche en G eochimie et en G eochronologie, GEOTOP, Universit e du Qu ebec a Montr eal, CP 8888 Succ. A, Montr eal, Quebec H3C 3P8, Canada e Departamento de Geologia, Universidade Federal de Ouro Preto, Morro do Cruzeiro, Bauxita, 45400-000 Ouro Preto, Minas Gerais, Brazil article info Article history: Received 13 February 2014 Accepted 18 December 2014 Available online 25 December 2014 Keywords: Lagoa Real uranium deposit Metasomatic alteration UePb mineralization age Metallogenetic implications abstract 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 UePb method to date zircon and titanite grains from the S~ ao Tim oteo granitoid, and albite-rich rocks from the Lagoa Real district in order to assess the age of granite emplacement, defor- mation/metamorphism and uranium mineralization. The isotopic data support the following sequence of events (i) 1746 ± 5 Ma e emplacement of the S~ ao Tim oteo granitoid (UePb 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 S~ ao Tim oteo granitoid and emplacement of the uranium mineralization (U ePb titanite age on an albite-rich sample); (iii) 480 Ma metamorphism, remobilization and Pb loss (UePb titanite age for the gneiss sample), during the nucleation of shear zones related to the collision between the S~ ao 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. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The Lagoa Real granitic-gneiss complex in Bahia State, north- eastern Brazil, hosts several uranium-enriched zones and com- prises the most important uranium province in Brazil (Figs. 1 and 2). A series of orebodies are known from thirty eight anomalies distributed over an area of 1200 km 2 , roughly along three semi- arched lineaments that cover an approximate extension of 35 km. The orebodies contain a total reserve of ca. 112,000 metric tons of U 3 O 8 (Brito et al., 1984; Matos et al., 2003; Matos and Villegas, 2010). Uranium production initiated in 1999 by Indústrias Nucle- ares do Brasil (INB), and 300 tons per year of uranium concentrate are produced from seven orebodies exploited at the northern Cachoeira open-pit mine (http://www.inb.gov.br; Matos and Villegas, 2010). Roughly 3.700 tons of U 3 O 8 have already been produced by INB. The uranium deposits are associated with rocks dominated by plagioclase (albite ± oligoclase) and albitites, which are the product of extensive, high-temperature metasomatic alteration of granitic- gneissic rocks, mainly in the form of sodium enrichment and silica depletion, accompanied by oxidation of the original Fe þ2 -dominant phases (e.g., Lobato and Fyfe, 1990). Lithotypes dominated by calcium-rich oligoclasites host some orebodies along the lineament suggesting NaeCa metasomatic alteration (Raposo and Matos, 1982; Raposo et al., 1984; Cruz, 2004). * Corresponding author. Tel.: þ55 31 96120791, þ55 31 34095443; fax: þ55 31 34095410. E-mail address: llobato.ufmg@gmail.com (L.M. Lobato). 1 In memoriam. Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames http://dx.doi.org/10.1016/j.jsames.2014.12.005 0895-9811/© 2015 Elsevier Ltd. All rights reserved. Journal of South American Earth Sciences 58 (2015) 129e140