Abstract: Nineteen elements were determined in four different grain size fractions of a bulk geological material from Cerro Impacto for a study of the physical (mechanical) concentration process of different elements based upon the hardness of the different minerals. The analysis was performed by excitation of the sample with a high, slow neutron flux followed by gamma-ray spectroscopy with both a conventional Ge(Li) high-energy detector and a low-energy photon detector (LEPD). The accuracy of this method was studied with the use of two standard reference materials, SY-2 and SY-3, which are similar to the real samples. The values determined were also compared with a secondary target x-ray fluorescence method for all the elements that were suitable to both methods. Actually, the x-ray fluorescence method was found to be more complementary than competitive.

Abstract: A simple procedure is proposed for the calculation of the absorption correction factor in electron-probe x-ray microanalysis. It is based on the concept of an effective depth of x-ray production, assuming a rectangular depth distribution function for x-ray generation. This effective x-ray production depth is expressed as a fraction of the x-ray excitation depth given by Whelan's expression. Adequate values for this fraction are presented. Two versions are considered. In the first the effective x-ray production is a function of both the characteristic x-ray energy and the atomic numbers of the matrix elements, whereas in the second one, which is indicated for routine use, the energy dependence is neglected. Calculations pointed to satisfactory results, even for low x-ray energies and high overvoltages.