Determination of uranium concentrations and activity ratios in silicates by alpha spectrometry: application to the volcanic rocks from the Trindade and Martin Vaz Islands (Brazil)

A detailed radiochemical procedure for alpha spectrometry measurements of uranium concentrations and of 234U/238U activity ratios in silicates is presented. The described chemical processing is characterized by relatively high uranium yields, in the range of 51–89%. The application of this chemical procedure to geological standards allowed estimating a reproducibility of the alpha spectrometry uranium measurements on the order of 3.5%. As an application example, the procedure was used in the analysis of quaternary volcanic rocks from the Trindade and Martin Vaz Islands, Brazil.