STUDYING POTASSIUM-SODIUM AND CALCIUM-SODIUM FELDSPARS BY X-RAY-PHYSICAL METHODS
A comprehensive study of rock includes petrographic and petrophysical methods for analyzing core sections (rock samples shaped as thin plates). The petrographic method consists in qualitatively determining the composition of the rock and semi-quantitatively calculating specific minerals in the thin section. The petrophysical method is aimed at evaluating the porosity, permeability, water holding capacity, and other properties of core sections. The matrix of collectors of Western Siberia is known to consist of quartz, plagioclase (Ca-Na feldspar), and K-Na feldspar. Feldspars are the most important family of rock-forming minerals and make up 60% of the earth's crust. Most feldspars are part of the NaAlSi3O8-KAlSi3O8-CaAl2Si2O8 ternary system, and the content of the anorthite component in alkaline feldspars (K-Na feldspars) and the orthoclase component in Ca-Na feldspars, as a rule, does not exceed 5-10 %mol. All the crystal structures of feldspar are based on a similar Si-Al-tetrahedral framework composed of four-membered rings [AlSi3O8]. One of the effective methods of petrophysical analysis is the X-ray structural analysis method, which is used to determine the quantitative content of minerals. However, X-ray diffraction analysis produces similar replicas of diffractograms for various feldspars due to the similarity of their Si-Al tetrahedral frameworks. Therefore, the use of X-ray analysis in studying feldspars is insufficient, and it is necessary to additionally apply elemental X-ray fluorescence analysis. In turn, X-ray fluorescence analysis does not allow to separate the peaks of the elements of potassium and calcium in minerals without the help of complex energy dispersive analyzers equipped with crystal analyzers. In this regard, the purpose of this study was to identify the optimal conditions for the separation and selective quantitative analysis of K-Na and Ca-Na feldspars using domestic diffractometers of the DRON type, equipped with a Si (Li) detector. In this regard, this report has developed a method for quantitative x-ray and phase analysis for the selective determination of calcium and potassium feldspar concentrations. A solution is proposed for the problem of separating the peaks of the characteristic radiation produced by the elements of these minerals. The conditions and optimal parameters of X-ray fluorescence and X-ray phase analysis are established. To determine the total mineral content, it was proposed to use X-ray phase analysis, to determine the calcium concentration - X-ray fluorescence analysis using an X-ray tube with a titanium anode and a scandium filter. Thus, for the study of feldspar in the composition of minerals presents a new X-ray analysis method, which is characterized by increased fastness and accuracy.