X-ray CT observation of minute dendritic groundmass crystals in the volcanic ejecta from the Shinmoedake volcano

Abstract

We obtained high-resolution X-ray CT images of the submicron scale plagioclase dendrites at SPring-8 BL47XU. The samples are lava fragments collected at the impact crater created by the vulcanian explosion of the Shinmoedake volcano on 1^st February, 2011. The dendrite branch spacing of plagioclase was ca. 500 nm. The pyroxenes and Fe-Ti oxides of <10 μm were also imaged. It was revealed that the three dimensional morphology of these plagioclase crystals were more complex than expected from the observation of a cross section. The growth of groundmass crystals might have continued after the emplacement of the volcanic bomb.