Figure 3

Fractions of mantle-derived He in the surface sediments of the submarine mud volcano off Tanegashima Island estimated in this study. Also plotted are the fractions of mantle-derived He in the sediments in the forearc region around Japan and the fraction of mantle-derived He in the surface sediments of submarine mud volcanoes in the Gulf of Cadiz. References are, respectively, as follows: a: Tomonaga et al.50, b: Wiersberg et al.56, c: Toki et al.55, d: Sano and Wakita57, e: Toki et al.58, f: Tsunogai et al.59, g: Nuzzo et al.20.