Temperature of the sub-arc mantle constrained by ejecta from Akita-Komagatake volcano

Abstract

To constrain the thermal structure of the upper mantle in the NE Japan arc, the conditions of magma generation were estimated for basalts from Akita-Komagatake volcano, using a petrological approach. We estimated that the primary magma was generated by 16% partial melting of the mantle with 0.54 wt.% H₂O at 1298°C and 14.2 kbar. This result suggests that the temperature of the sub-arc mantle at 45 km depth is ~1300°C, which is higher than those estimated by geophysical studies by >100°C.