Development of helium isotopic database in Japan

Kusano, Tomohiro; Asamori, Koichi; Umeda, Koji

We constructed "Helium Isotopic Database in Japan", which includes isotope ratios of noble gases and chemical compositions of gas samples collected from hot springs and water wells. The helium isotopes are excellent natural tracers for indicating the presence of mantle derived volatiles, because they are chemically inert and thus conserved in crustal rock-water systems. It is common knowledge that mantle degassing does not occur homogeneously over the Earth's surface. The He/He ratios higher than the typical crustal values are interpreted to indicate that transfer of mantle volatiles into the crust by processes or mechanisms such as magmatic intrusion, faulting. In particular the spatial variation of helium isotope ratios could provide a valuable information to identify volcanic regions and tectonically active areas. The database was compiled geochemical data of groundwater from 108 published papers. As a result of the data compiling, the database has 1728 Helium isotopic data.