Abstract
Plagioclases in common volcanic rocks (basalt to rhyolite) were analyzed using an electron probe microanalyzer (JCXA-733) under the following condition: accelerating voltage=25 kV, beam current at Faraday cup=0.02 μA, line=Lα, crystal=PET, and measurement time=120 sec for the peak (line) and 60 sec (×2) for the backgrounds. The statistical lower limit of detection is SrO=0.05%, and the standard deviation (1σ) is 0.03% for SrO≤0.5%. The analytical results imply that Sr content of plagioclase generally decreases as crystallization progresses in closed magma systems of common volcanic rocks. Also some applications using this analytical method have been briefly discussed.
