Search for an ''Oklo Phenomenon'' in the Northeastern regions of Brazil

Rocks samples from the Northeastern region of Brazil were analysed for their 235U isotopic abundance, in search for the occurrence of an ''Oklo Phenomenon'' here. The samples were collected in locations that could have been connected to the African continent, according to the continental-drift theory, in accordance to the Francevillian formations in the Gabon Republic, in which place the Oklo natural fossil reactor is situated. Two methods were used for the determination of the 235U abundance: activation analysis followed by high resolution gamma-ray spectrometry and activation analysis by delayed neutron counting. No evidence of 235U depletion was found in the rock samples analysed. (author)