Cumulative neutron activation of short-lived radionuclides for the analysis of large samples in mineral exploration

Cumulative neutron activation is used to determine mg/kg concentrations of gold in rock samples, weighing 10 g. Twenty 0.5 g replicates are irradiated in an epithermal-neutron flux for 5 s and counted for 14 s. The twenty spectra are summed, and gold is measured with the 279 keV gamma-ray of^197mAu (7.2 s). Total analysis time for a 10 g sample is 400 s and detection limits around 2 mg/kg are achieved in gold ores, sulfides and silicates.