Magma plumbing system of the Aso-3 large pyroclastic eruption cycle atn Aso volcano, Southwest Japan: Petrological constraint on the formationn of a compositionally stratified magma chamber

摘要

Aso volcano has the largest caldera (18 x 25 km in diameter) in the southwestern japan Island Arc, and it formed as the result of four large (VEI = 6-7) pyroclastic-eruption cycles. We study the penultimate large eruption cycle, the Aso-3 cycle, which occurred 123 ka with an ejecta volume of more than 150 km(3). The processes in the pre-eruptive magma chamber and the magma genesis of the Aso-3 cycle were inferred from geological data, phenocryst chemistry, and whole-rock chemical and Sr-, Nd-, a