Major element versus MgO variation diagram of melt compositions. Major element versus MgO variation diagram of melt compositions obtained through hydrous melting experiments by Hamada and Fujii (2008). (a) SiO2 (wt.%). (b) Al2O3 (wt.%). (c) Al2O3/SiO2 weight ratio. (d) FeO* (wt.%). (e) CaO (wt.%). Liquid compositions obtained from the volcanic rocks from the Izu-Oshima volcano are also shown for comparison with experimental results. Fe content is given as FeO* (total iron), and the compositions of both natural volcanic rocks and experimental liquids are normalized to 100 wt.%.