Figure 4
Map of estimated H 2 O content in relatively primitive basalt from the Northeast Japan and Izu arcs. Volcanoes represented by larger symbols are listed in Table 2. Numbers near a circular symbol shows the H2O content of pre-eruptive basalt estimated by Equation 1 and are listed in Table 2. Superscript ‘a’ indicates that the estimated water content has uncertainty because the reference used had no frequency distribution of plagioclase phenocryst compositions (Iwate volcano: Kuritani et al. 2014a; Funagata volcano: Fujinawa, 1982). Superscript ‘b’ indicates that the reference used suggested the occurrence of magma mixing. In this case, although the water content was not estimated, the compositions of most anorthite-rich plagioclase is shown by circular symbols (Chokai volcano: Hayashi and Aoki 1985).