The use of the uranium isotopic model on the study of aquifers at Morro do Ferro, Pocos de Caldas, Minas Gerais State, Brazil

Uranium isotopic analyses were performed in groundwaters from several boreholes drilled at the thorium and rare earth deposit located at Morro do Ferro, near the centre of the Pocos de Caldas Plateau, Minas Gerais State, Brazil. The samples were collected during dry and wet periods, proceeding from aquifers developed in the weathered mantle due to in situ intense alteration, with the weathered zone establishing an argillaceous laterite greater than 100 m thick. The 234 U/238 U activity ratio and U content measured for each sample by alpha spectrometry were used to evaluate the applicability in the area of the model developed to deduce proportions of groundwaters in a mixture. The influence of the rainfall on the utilization of the uranium isotopic model was considered, and also it was possible to suggest which boreholes would be able to supply samples representing different systems of circulation of groundwaters. (author). 5 figs., 2 tabs