About the assessment of gold concentrations in tiny inclusions within sulfide mineral matrix: An electron microprobe study

Abstract

A method for estimating the native gold composition in micron‐ and submicron‐sized inclusions in the matrix of a sulfide mineral with electron probe X‐ray microanalysis is proposed. Such inclusion sizes are comparable with or less than the X‐ray generation volume, and therefore, the analytical signal is a mixture of signals from the matrix elements and the inclusion elements, which significantly complicates the quantification. The proposed procedure is based upon the extrapolation of the trend of the dependence of the measured elemental contents in the inclusions, for example, Au or Ag, versus the content of matrix elements, namely, S, Fe, and As. To define the influence of the inclusion size on the intensity of the excited X‐rays, the trajectories of the electrons in a sample were simulated by the Monte Carlo method. It was found that the trends in the behavior calculated by the Monte Carlo method are consistent with the data measurements of an artificial pyrite sample with a sprayed pure gold layer (approximately 1 μm thick) arranged perpendicular to the sample surface. The measurements were performed on a Superprobe JXA‐8200 microanalyzer. The proposed method was demonstrated by analyzing natural, finely dispersed gold inclusions in arsenopyrite. This approach made it possible to evaluate the Au and Ag contents in the approximately 1 μm inclusions and assess the uncertainty of the measurement.

Lithochemical Stream Sediments of the Dukat Gold–Silver Ore-Forming System (North–East of Russia)

“…Substance composition determination was performed through local analysis methods using electron probe microanalysis (EPMA) on the JXA-8200 SuperProbe (JEOL Ltd., Tokyo, Japan) microanalyzer in accordance with the available techniques [93][94][95][96]. Grain surfaces were examined through a scanning electron microscope JXA-8200 SuperProbe (JEOL Ltd., Tokyo, Japan) with backscattered and secondary electrons to detect inclusions containing ore elements.…”

“…The chemical composition of the inclusions found was determined by the survey monitoring and recalculating the recorded relative intensities in the concentration using the JXA-8200 SuperProbe microanalyzer software (Version 01.42, JEOL Ltd., Tokyo, Japan). In determining the composition of finely dispersed gold inclusions with a size smaller than the locality of the EPMA method, matrix effects were taken into account following the method of content trends [95,96].…”

“…In the course of the work, it became obvious that the study of ore element BFs in loose alluvial sediments of watercourses is ineffective using traditional mineralogical methods. The successful solution of such types of tasks is directly related to the determination of the substance composition in micron inclusions and only through local methods, such as EPMA [93][94][95][96]. The binding forms of Au, Ag, Hg, Sb, As, Pb and Zn, the basic element indicators for the Au-Ag mineralization type, were investigated.…”

“…Among the Ag sulphosalts, pyrargyrite and proustite were observed-minerals that are characteristic only of the supra-ore and upper-ore horizons of the Dukat deposit and that, with a sufficient degree of probability, can speak in favor of the positive prediction of deep mineralization. inclusions and only through local methods, such as EPMA [93][94][95][96]. The binding forms of Au, Ag, Hg, Sb, As, Pb and Zn, the basic element indicators for the Au-Ag mineralization type, were investigated.…”

Microinclusions and Impurities in Sulfide Minerals of the Natalkinskoye Gold Deposit (North-East of Russia) According to the Rsma

“…Увеличилось количество определяемых элементов. Изучение проводилось с помощью метода РСМА по методикам [3,4]. Сульфиды монтировались в брикетированные аншлифы и изучались на микроанализаторе JXA-8200 SuperProbe (JEOL Ltd., Япония), оснащенном волновыми и ЭДС-спектрометрами.…”