Determination of gold in Romanian auriferous alluvial sands and rocks by 14 MeV neutron activation analysis

摘要

In this work a complex study of the nuclear and spectral interferences which appear in gold determination by 14 MeV neutron activation analysis of Romanian auriferous alluvial sands and rocks has been accomplished. The contribution of the nuclear interfering elements - Hg and Pt - to the concentration of gold in the samples is minimum in the case of the nuclear reactions ~(197)Au(n, 2n)~(196)Au, ~(197)Au (n,2n)~(196m)Au and ~(197)Au(n, n′)~(197m)Au. As regards the spectral interferences, these are minimum in the case of using the reactions ~(197)Au(n, n′)~(197m)Au and ~(197)Au (n, 2n)~(196)Au and are due to Rb, Ti and V for the short irradiation and to Se for the long irradiation. We propose two methods of gold determination in auriferous alluvial sands and rocks in the range 20-2500 ppm - the minimum value of 20 ppm being at the level of an economic extraction - in the optima conditions established by us so that the systematic errors of analysis due to the gold accompanying elements should be considerably diminished: a method using short irradiation (25 s) and Nal(Tl) spectrometry for the measuring of the induced gamma radioactivity in the samples and a method using long irradiation (3000 s) and Ge(Li) spectrometry. The data presented in this paper can be adapted by other analysts to the rapid determination of gold in a variety of alluvial sands and rocks.