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.
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).