Timing and trigger of arc volcanism controlled by fluid flushing from subducting slab

Abstract

We present ²³⁸U-²³⁰Th-²²⁶Ra systematics in lavas from Miyakejima volcano, Izu arc, Japan, together with major element, trace element and Sr-Nd-Pb isotopic compositions, to estimate the timescale of magmatic processes beneath an island arc. ²³⁸U-²³⁰Th-²²⁶Ra disequilibria observed in Miyakejima lavas with large excesses of ²³⁸U and ²²⁶Ra to ²³⁰Th imply metasomatism of depleted mantle by fluid related processes. Our data reveal that fluid components released from the slab ascend rapidly through the mantle wedge (>50m/yr), and that individual stages of subaerial volcanism are induced by flushing of different fluid batches to the mantle wedge with a periodicity of 1-13kyr. This indicates that arc magmatism is controlled by pulsed release of fluid from the slab occurring on such a small timescale, which might be related to the occurrence of earthquakes in the subducting slab.