Temporal change of magma plumbing system in activities of Old-Kumanodake and Nakamaruyama edifices of Zao volcano, NE Japan

Abstract

The products of Old-Kumanodake and Nakamaruyama edifices are divided into lower, middle, and upper units. All rocks are mixed calc-alkaline andesites. The whole rock compositional data show that new mafic magma with distinct compositions started to ascent in the period of the middle unit. Further, the minaralogic features indicate the higher-temperature felsic end-member magma was newly formed at the middle unit time which coexisted with the lower-temperature one. The latter disappeared at the upper unit time.