U - Isotopic Model as a Prospecting Technique in the Morro do Ferro Thorium Deposit, Brazil

Abstract

Uranium isotopic analyses were perforæd for groundwater eamples tom sewral borehoþs d¡illed at Mono do Femo, a thorir¡m and rare earth dopoeit locabd on the Poços de Caldas Plateau, Minas Gerais State, Brazil. The ¡lata on the isotopic concentrations of dissolved r¡ranium werp used to evaluate the applicability of the U-isotopic model developed by Cowart & Osmnd (1980) in the area. The 234U/238U acvity ratios for the dissolved U in these groundwaters wprebetween t arnrd 2 a¡rd the U content varied from.O.Ol up to O.72 ppb. These results show, that active uranium dissolution is occurring at Morro do Ferro. The enhanced 234U/238U activity ratios for the dissolved U are attributed to preferential etching of 234U. The results also suggest that the "nomal oxidized" classification of the grandwater samples in terms of their position relative to the.U mineralizatin could be better representat¡ve of the studied system instead of thel 'normal reduced" classification indicated by the model of Cowart & Osmond (1980).