Considerations on the formation age of Mikadoishi Lava Dome at Towada volcano, Northeast Japan

Abstract

    The formation age of Mikadoishi Lava Dome at Towada volcano was estimated based on the petrological features of eruptive rocks during the post-caldera stage in Towada volcano. The lava dome has dacite compositions (66.4 wt.% SiO₂) and contains plagioclase, clinopyroxene, orthopyroxene and Fe-Ti oxide phenocrysts. The petrological features show that the lava dome does not correlate with any tephras from the post-caldera stage. This indicates that the lava dome eruption was not accompanied with notable pyroclastic eruptions. The formation age of the Mikadoishi Lava Dome can be estimated to be sometime within 11.7-2.7 cal kyr BP on the basis of the temporal change of magma compositions in the post-caldera stage.