Analysis of uranium distribution in rocks by μ-PIXE

We examined distributions of U as well as P, Ca, Fe and Ti in rock samples collected at the Koongarra uranium deposit, Australia, using a micro-proton-induced X-ray emission (μ-PIXE) analyzing system developed in the TIARA facility of Japan Atomic Energy Research Institute (JAERI). The conventional scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) was also applied to identify a U-bearing phosphate as saleeite, and to examine the distributions of the above elements to clarify relative advantages of μ-PIXE. The advantages of μ-PIXE are as follows: (1) the spatial resolution of μ-PIXE, about 0.8 μm2, is higher than that of SEM-EDS, about 7 μm2, (2) the contrast of elemental maps by μ-PIXE is better than that by SEM-EDS, (3) μ-PIXE detection of U using its L-line gives more reliable U distribution when clay minerals containing potassium are present. It is concluded that μ-PIXE is one of the best techniques that allows U to be accurately analyzed and mapped in K-bearing minerals, using its L-line