NAKAI, Shun'ichi

Earthquake Research Institute

Office: ERI-419
TEL: +81-3-5841-5698
FAX: +81-3-5802-3391

Research Field


Current Research

My group is working on developing new analytical techniques for geochemical samples, including volcanic rocks, carbonate nodules to decipher the records hidden in the samples. Mantle melting, subduction of oceanic crust and surface sediment into the mantle can produce mantle heterogeneity. In addition, core-mantle interaction may also play an important role. Putting chronological constraints on variety of geochemical processes, such as volcanic eruption, fluid migration in subduction zone, is another important target for us. To tackle the challenging problem, we are developing analytical methods using analytical apparatus, including an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) installed in our institute.Our achievements include developing a method for tungsten isotope analysis, lithium isotope analysis, uranium-thorium radioactive disequilibrium dating. These achievements are being applied for the projects to reveal core-mantle interaction (using tungsten isotope), to reveal material transfer in subduction zone (lithium isotope), to put chronological constraints on magma transfer in subduction zone, activity of sea floor methane seeps and sulfide minerals in submarine hydrothermal systems (uranium-thorium radioactive disequilibrium dating).We also developed a technique of micro-drilling Sr isotope analysis and applied it to plagioclase from Unzen volcano.

Representative Publications

1. Nakai, S., Maeda, Y, and. Nakada,S., Common origin of plagioclase in last three eruptions of Unzen volcano, Japan. J. Volcanol. Geotherm. Res. 175, 181-188 (2008).
2. Takamasa, A., Nakai, S., Sahoo, Y., Hanyu, T., Tatsumi, Y. W isotope compositions of oceanic islands basalts from French Polynesia and their meaning for core-mantle interaction. Chemical Geology, 260, 37-46 (2009).
3. Takamasa, A., Nakai, S., Sato, F., Toyoda, S., Banerjee, D., and Ishibashi, J., U-Th radioactive disequilibrium and ESR dating of a barite-containing sulfide crust from South Mariana Trough. Quaternary Geochronology, 15, 38-46 (2013).