Rapid Determination of Major and Trace Elements in Geological Material with Proton-Induced X-Ray and Gamma-Ray Emission

The simultaneous detection of proton-induced X-rays and gamma-rays enables rapid determination of both major and trace elements in thick homogeneous samples. Using protons of energy 2.55 MeV, the atomic numbers of the elements detectable with this technique were Z=3, 5, 9, 11–13 from gamma-ray analysis and Z=13–92 from X-ray analysis. Thick target concentrations were determined from a thoroughly made thin target calibration and from matrix-dependent conversion factors calculated from fundamental parameters. The major compositions of samples needed in these calculations are derived in an iterative procedure using the spectra recorded. The method proposed has been tested on six USGS rock standards. Detection limits for one of the standards are presented. Approximately 20 elements were detected in each sample 5 min irradiations. For elements well above their detection limits, the results are typically accurate to within 5%. The precision of repeated day-to-day analysis is about 2% (one standard deviation)