Simple measurement of the major elemental composition with SEM-EDX and its application to a geological survey

Abstract

This study focused on Scanning Electron Microscope/Energy Dispersive X-ray Spectroscopy (SEM-EDX) for the conventional determination of major elements contents in rock samples. The measured elements were Na2O, MgO, Al2O3, SiO2, K2O, CaO, TiO2, and Fe2O3. The appropriate preparation conditions were the sample grain size of less than 8.0 µm in median size, and an analysis area wider than 12.15 mm2 in SEM-EDX. The analytical results indicated that the relative standard deviation of measured element content fell within almost 10 %. By comparing between the SEM-EDX and XRF analysis, SEM-EDX is quantifiable to be the relative standard error within 7.7 % (Na2O), 8.6 % (MgO), 5.9 % (Al2O3), 1.9 % (SiO2), 8.7 % (K2O), 10.0 % (CaO), 15.9 % (TiO2), 18.7 % (Fe2O3). The application of this method to a geological survey indicated that the constituent minerals in the strata were predictable by examining the relationship with the major elements contents. Sample screening preceding an accurate determination of the elements and minerals composition is of great concern, because many analytical data are used for understanding the geochemical features of the strata. The SEMEDX method proposed herein enables the measurement of major elements and the prediction of constituent minerals in the strata, and thus can be used as a screening method prior to an accurate geochemical analysis.