The Lagoa Real Uranium Province: polycyclic evolution in the Brazilian geochronological record

The Lagoa Real uranium province (LRUP) is the main Brazilian target for uranium. Their geochronological studies began in the 80s and provided controversial ages for mineralization. Since then, advances in geochronological methods, increased local petrological data, and knowledge of the uranium cycle have helped geosciences understand crust and mantle behavior over time. As a result, recent geochronological studies developed by CDTN researchers have now begun to reinterpret the evolution of the LRUP.

These studies dated metasomatic  U-ore bodies providing ages between 545 Ma to 520 Ma (in situ U–Pb dating of andradite and titanite, Santos et al., 2023; Journal of South America Earth Science) coeval with the late Pan-African Cycle. Geochronological studies were also carried out on the host rocks (A-Type granites) of the mineralized bodies, providing ages between 1762 Ma to 1741 Ma (U–Pb dating of magmatic Zircon, Amorim et al., 2022; Journal of South America Earth Science), coeval to bimodal magmatism well documented in Brazil and Africa.

Although some of the data obtained suggest that granites might not be the source of uranium, their volcanic expression (metaryolites located to the NW of the LRUP) could be a good candidate. Thus, the uranium mobilization began before the metasomatism, through magmatic processes, coeval with the Post-Archean Uranium Recycling, a global event that incorporates U in the crust from the mantle. Furthermore, preliminary macroscopic and microscopic data from gneisses show evidence of partial melting related to regional metamorphism that may have occurred before metasomatism. This process generated Neoproterozoic uranium deposits in Namibia, at the Southern of the African counterpart of Brazil. Therefore, LRUP could result from overlapping processes in central Brazil accompanied by crustal differentiation episodes leading to a polycyclic evolution.