Chemical evolution of magma toward the catastrophic eruption at Kikai Caldera recorded in Chikyu SCORE tephra

Abstract

Kikai submarine caldera caused several catastrophic eruptions. In order to understand the eruption processes and magmatic evolution, we measured chemical composition of tephra collected via the SCORE program with D/V Chikyu. We used submarine tephra from the K-Ah eruption (7300 years ago), that from the K-Tz eruption (95000 years ago), and that intercalated between the two catastrophic eruptions, the age of which is approximately 40000 years ago or younger. The tephra from the K-Tz eruption is predominated by felsic pyroclasts, but the presence of a few mafic pyroclasts suggests the contribution of mafic melts during the K-Tz eruption. The tephra intercalated between the two catastrophic eruptions have chemical composition similar to those of K-Ah, implying that the storage of felsic magmas commenced at least 40000 years ago toward the next catastrophic eruption of K-Ah.