Generation of rhyolite magmas by melting of subducting sediments in Shodo‐Shima island, Southwest Japan, and its bearing on the origin of high‐Mg andesites

Geochemical characteristics of rhyolites from the Miocene Setouchi volcanic belt in the Southwest Japan arc were examined. The following observations may be best explained by the derivation of rhyolite magmas by melting of subducting sediments as follows. (i) Sr‐Nd‐Pb isotope compositions of Setouchi rhyolites are close to those of the local trench‐fill sediments; (ii) major element compositions of rhyolites are identical to those of experimentally produced sediment melts; and (iii) concentrations of incompatible elements in rhyolites are consistent with partial melting of the local trench‐fill sediments in the presence of residual garnet. Furthermore, trace element and isotope signatures of Setouchi high‐Mg andesites can be also rationalized by interaction of such rhyolitic sediment melts with overlying mantle peridotites.