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Top Page  >  Isotope Geochemistry Group

Isotope Geochemistry Group

To understand global environmental changes, and the mechanisms causing these changes, it is necessary to evaluate quantitatively the cycling of subsurface materials. To achieve this goal, the Geochemical Research Group develops study of isotopic tracers from basic to frontier sciences (isotopes of Li, Sr, B, Pb, Mg, Ca, etc.).

Advanced research on isotope geochemistry

  • Establishment of 'metal' isotopic tracers in carbonates to understand paleoenvironmental proxies.
  • Elucidation of the presence and role of fluids within fault zones during co-seismic events.

Development of advanced techniques for isotope analysis

  • Precise isotope analyses of non-radiogenic stable isotopes using a multiple collector ICP mass spectrometer and a thermal ionization mass spectrometer (Li, B, Mg, etc.).
  • Precise isotope analysis of very small amount of Pb (<1ng) using an ICP mass spectrometer with multiple ion counting system.

Joint research and education

  • Research and education in collaborative chair of Graduate School of Science, Hiroshima University.
  • Understandings of environmental behavior of antimony on the basis of speciation and isotopic analyses (founded by Ministry of Environment 2008-2009, head: Dr. Y. Takahashi, Hiroshima University).
  • Research of Oceanic Anoxic Events (OAE) and its paleo-environmental impact based on Pb isotope analysis of sediments (head: Dr. J. Kuroda, IFREE, JAMSTEC).

Joint research with Hiroshima University using a multiple collector ICP mass spectrometer.


Group Leader
Tsuyoshi Ishikawa
Deputy Group Leader
Masaharu Tanimizu
Deputy Group Leader
Motoo Ito
Shigeyuki Wakaki


  • Isotope Geochemistry
  • Sedimentology


  • Takayanagi, H., Nakayama, Y., Ishikawa, T., Nagaishi, K., Iryu, Y. (2010) Sr isotope composition of island-surface dolomites at Kita-daito-jima, northern Philippine Sea. The Journal of the Geological Society of Japan, in press.
  • Hirono, T., Ujiie, K., Ishikawa, T., Mishima, T., Hamada, Y., Tanimizu, M., Soh, W., and Kinoshita, M. (2009). Estimation of temperature rise in a shallow slip zone of the megasplay fault in the Nankai Trough. Tectonophysics. Vol. 478, Issues 3-4, 215-220. doi:10.1016/j.tecto.2009.08.001
  • Machiyama, H., Kinoshita, M., Takeuchi, R., Matsumoto, R., Yamano, M., Hamamoto, H., Hiromatsu, M., Satoh, M., Komatsubara, J. (2009) Heat flow distribution around the Joetsu gas hydrate field, Western Joetsu Basin, Eastern Margin of the Japan Sea. Journal of Geography. 118(5) 986-1007. 2009.
  • Kashiwabara, T., Takahashi, Y., Tanimizu, M. (2009) A XAFS study on the mechanism of isotopic fractionation of molybdenum during its adsorption on ferromanganese oxides. Geochemical Journal, Vol. 43 (No.6), e31-e36.
    • Nagaishi, K. and Ishikawa, T. (2009) A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples. Geochemical Journal, Vol. 43 (No. 2), PP133-141.


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