Noritoshi Morikawa:

Research Scientist

Crustal Fluid Team, Geological Survey of Japan

I am a geochemist focusing on noble gas hydro-geochemistry of groundwater and hot springs. As a post-doctoral fellow, I started to research dissolved helium isotopes in deep groundwater. Now I am working at the Geological Survey of Japan with many colleagues and have extended my research field to groundwater from deep boreholes, groundwater around active volcanoes, hot springs etc.

My main research fields and subjects are:

• (1) Groundwater dating using helium isotope ratios and ⁴He concentrations in geologically active regions. I try to estimate the residence time of groundwater which has mixed with groundwater of different origins.
• (2) Unusually high temperature thermal brines in the fore-arc region of southwest Japan, which are not related to Quaternary volcanoes. Helium isotopes in these hot springs are high, sometimes up to 8 Ra. I study the origin of these unusual brines.
• (3) Groundwaters around active volcanoes. I have extensively sampled and measured helium isotopes in groundwater around active volcanoes such as Unzen and Satsuma-Iwojima, and I am investigating the spatial distribution and the flux of the magmatic component.
• (4) The behavior of heavier noble gases in fluids, because elemental and isotopic fractionation of noble gases should record the dynamics of fluid migration.