X-RAY SPECTRAL MICROANALYSIS OF ROCK-FORMING MINERALS AND IMPURITIES ON AN INCA ENERGY+ SYSTEM INTEGRATED WITH A JSM-6490LV SCANNING ELECTRON MICROSCOPE

The chemical composition and morphology of rock-forming minerals have been studied. The metrological characteristics are evaluated and the results of the electron probe analysis of the chemical composition of rock-forming minerals and impurities in them during the registration of X-ray radiation by spectrometry methods with wave (WDS) and energy (EDS) dispersion are compared. The measurements were performed on an INCA ENERGY + microprobe analysis system (Oxford instruments), consisting of an Inca Energy 450 EDS spectrometer and an Inca Wawe 500 wave dispersion spectrometer installed on a JSM-6490LV (Jeol) scanning electron microscope. The object of the study was a sample prepared from phosphorite nodule (the Kolky formation of the Mohyliv-Podilskyi series of the Upper Vendian of Volyn). It was found that in the range of the content of the main components of minerals (C > 10%), the coefficient of variation characterizing the convergence of a single determination is about 2% when registering radiation by the WDS method and about 2.5% for the EDS method. Accordingly, in the region of the content of minor components (1 < C < 10%), the coefficient of variation is 8 and 10 %, and in the region of component impurities (0.3 < C < 1%), 15 and 25%. With an even lower content, EDS analysis is practically impossible. The study shows that when determining the main and secondary components of rock-forming minerals, the registration methods using EDS and WDS are comparable in accuracy. When determining impurity components, the EDS method is noticeably inferior to the WDS method, and at even lower concentrations it is generally not applicable. The EDS method is easier to implement, works in parallel mode, i.e. analyzes at the same time the analytical lines of all the elements and is able to produce results in a short time after turning on the device. The WDS method requires a significant investment of time in the preparation and implementation of the analysis protocol, but it is capable of conducting analysis with high accuracy and resolution, including when the content of the element being determined is below 1%. The technique described in this work is a generalization of part of the studies conducted by the author on the complex of electron probe analysis equipment at the Institute of Geological Sciences of the National Academy of Sciences of Ukraine.