Quantitative Electron Microprobe Analysis of Silicates Using Energy-Dispersive X-Ray Spectrometry

Abstract

The advantages of using a lithium-drifted silicon X-ray detector instead of conventional Bragg spectrometers in microprobe analysis include simplicity and speed of operation. Also electron beam damage to minerals can be almost eliminated, owing to the low probe current required. A procedure for quantitative analysis is outlined here, and its scope and limitations are discussed, with special reference to silicate analysis. Analyses of 34 silicates independently analysed by chemical methods and conventional probe analysis are given. Above about 0.2 wt. per cent (element) systematic differences between energy-dispersive and conventional probe results are hardly significant. There are some discrepancies between probe and chemical data, probably mostly due to errors in the latter (e.g. high A12O3 and low FeO). Concentrations below 0.2 per cent but above the theoretical limit of detection are sometimes not recorded. This is presumed to be due to slight over-correction for background, which could be rectified by a more complicated background correction procedure.