Optimizing SEM-EDX for fast, high-quality and non-destructive elemental analysis of glass†

Abstract

Advancements in scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) technologies have reached the point where rapid, fully quantitative, non-destructive and high-resolution acquisition of effectively all major element chemical information from polished sample material is possible. Here, we discuss optimisation parameters and demonstrate the data quality that can be achieved for SEM-EDX analysis of magmatic glass samples; glass represents a particular challenge due its lack of stoichiometry and potential for beam-induced element mobilisation. We test our approach through analysis of reference materials and demonstrate the advantages of SEM-EDX for several volcanic glasses that were previously investigated with electron probe micro-analysis (EPMA). SEM-EDX analysis is typically undertaken at a much lower beam current than EPMA, allowing for non-destructive analysis of geologic material that are sensitive to a higher beam current, such as sodium-rich glass. With careful instrument set-up, robust standardisation, and optimal experiment parameters, SEM-EDX analysis can achieve major and minor element data comparable with that collected via EPMA, with the exception of low abundance elements (those below 0.2 wt%). In addition, SEM-EDX analysis typically uses a smaller beam diameter and so permits analysis of smaller features than EPMA. Our results show that this technique can be potentially used as a quantitative tool on a wide range of geological materials with faster analysis, improved spatial resolution and cost advantages making it a complementary or alternative analytical method to EPMA.