A sample fusion technique for whole rock analysis with the electron microprobe

A technique has been devised for major element whole rock analysis using the electron microprobe. Rock powders are fused on a strip heater using a low voltage, high amperage source and quenched to form a glass bead in a container pressurized with argon. Sample weights of 20 mg to ~ 300 μg with run times of 20–60 sec produce sufficient material for analysis. Analyses of the fused samples compare favorably with those achieved by X-ray fluorescence and neutron activation for major elements in a wide range of silicate rock compositions. Analytical errors for major element concentrations are generally 5% or less. Alkali losses for Rb are ~10% at the 20 ppm level as determined by isotope dilution mass spectrometry. Sodium determinations compare favorably with those obtained by neutron activation analysis.