Comparison of three techniques for the determination of uranium and thorium in rocks

Abstract U and Th concentrations have been determined in a series of selected whole-rock samples, using three different techniques: neutron activation analysis (INAA), X-ray fluorescence spectrometry (XRF) and isotope dilution mass spectrometry (ID). The INAA technique yields U and Th data that are comparable with those obtained by ID over the entire concentration range studied. XRF only provides data with comparable precision at relatively high concentrations (> 10 ppm) but has the advantage of being able to determine other useful elements such as Rb, Sr, Pb and K. The choice between INAA and XRF therefore depends on the concentration levels anticipated, together with the overall requirements for the particular study.