Japan Geoscience Union Meeting 2014

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Symbol M (Multidisciplinary and Interdisciplinary) » M-TT Technology & Techniques

[M-TT42_2AM2] Frontiers in Geochemistry : Innovative approaches for Earth and Planetary Sciences

Fri. May 2, 2014 11:00 AM - 12:45 PM 314 (3F)

Convener:*Yusuke Yokoyama(Atmosphere and Ocean Research Institute, University of Tokyo), Hiroyuki Kagi(Geochemical Laboratory, Graduate School of Science, University of Tokyo), Shogo Tachibana(Department of Natural History Scieces, Hokkaido University), Takafumi Hirata(Graduate School of Science, Kyoto University), Urumu Tsunogai(Graduate School of Environmental Studies, Nagoya University), Katsuhiko Suzuki(Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology), Gen Shimoda(Geological Survey of Japan, AIST), Hirochika Sumino(Geochemical Research Center, Graduate School of Science, University of Tokyo), Hajime Obata(Marine inorganic chemistry division, Atmosphere and Ocean Research Institute, University of Tokyo), Yoshio Takahashi(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Tetsuya Yokoyama(Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology), Chair:Hiroyuki Kagi(Geochemical Laboratory, Graduate School of Science, University of Tokyo), Shogo Tachibana(Department of Natural History Scieces, Hokkaido University), Yusuke Yokoyama(Atmosphere and Ocean Research Institute, University of Tokyo)

11:15 AM - 11:30 AM

[MTT42-09] Cavity ring-down spectroscopy for the isotope ratio measurements of water from fluid inclusions in stalagmites

*Ryu UEMURA1, Masashi NAKAMOTO1, Masakazu GIBO1, Satoru MISHIMA1, Ryuji ASAMI2 (1.University of the Ryukyus, 2.University of the Ryukyus)

Keywords:Stable isotope, Fluid inclusion, Speleothem, Stalagmite, Paleoclimate, CRDS

Oxygen isotope record in stalagmites is useful to reconstruct past environmental changes. However, the interpretation of calcite isotope record is not straightforward because it is affected by various factors affect such as amount of precipitation and temperature. Water isotope composition of fluid inclusions, and oxygen isotope difference between water and host calcite, from stalagmite are potentially important proxies to estimate the paleo-temperature. Recently, infrared spectroscopy (IRIS) has been widely used for stable isotope ratio measurement of water. Unlike traditional isotope mass spectrometer (IRMS), the IRIS does not require pre-treatment processes (e.g., high-temperature furnace or equilibration device). A limitation of IRIS is that commercially available IRIS systems need large sample volume (1 - 2 micro litres) for liquid water measurement. In this study, we developed a custom-designed device suitable for precise measurement of smaller volume (0.05 to 0.20 microlitres) of water, and tested two extraction methods (thermal extraction and mechanical crushing). Oxygen and hydrogen isotope ratios of water were measured using cavity ring down spectroscopy (WS-CRDS Picarro L2130-i). Stalagmites samples were collected in several caves in Okinawa, Japan. Pieces of stalagmites (80-300mg) subsampled from homogeneous layers, and reproducibilities of the inclusion measurement were 0.2 permil for δ18O and 1 permil for δD. The measured δ18O and δD of inclusion water from recently grown stalagmites agrees with modern dripwaters, indicating that our extraction technique is useful to measure isotope ratios of past inclusion water.