Abstract
Forty-five hot spring samples in Japan with various hot spring types were measured their del37Cl values. Del37Cl values ranges from -1.62 to 0.97 permil. Hot spring with magmatic origin has higher positive del37Cl value (0.5-0.9) and that of fossil seawater has negative value. Matsushiro hot spring, which is typical magmatic origin, shows "oxygen-shift" on delD vs del18O diagram and can be extrapolated to the range of andesite magmatic water. Del37Cl also shows the correlation with del18O. From this relation, del37Cl value of andesite magmatic water was estimated to be 1.5 to 1.9 permil. This del37Cl value suggests that Cl in andesie magmatic water is mixture of mantle Cl (4.2_-_7.0 permil) and subducted seawater.
