Japan Geoscience Union Meeting 2014

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

[M-TT42_2AM1] Frontiers in Geochemistry : Innovative approaches for Earth and Planetary Sciences

Fri. May 2, 2014 9:00 AM - 10:50 AM 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:Yusuke Yokoyama(Atmosphere and Ocean Research Institute, University of Tokyo), Shogo Tachibana(Department of Natural History Scieces, Hokkaido University), Hiroyuki Kagi(Geochemical Laboratory, Graduate School of Science, University of Tokyo)

9:00 AM - 9:15 AM

[MTT42-01] Mass-independent fractionation of mercury stable isotopes in deep-sea hydrothermal systems

*Akinori TAKEUCHI1, Takashi TOMIYASU2, Hitoshi KODAMATANI2, Masahiro YAMAMOTO3, Katsumi MARUMO4 (1.National Institute for Environmental Studies, 2.Kagoshima University, 3.JAMSTEC, 4.University of Toyama)

Keywords:Mercury Isotope, MIF, Deep-sea Hydrothermal Systems, CV-MC-ICP/MS

It has been recognized that mercury (Hg) isotope analysis is an important new tool for identifying Hg source and tracking Hg transformations in the environment. Mass-dependent (MDF) and -independent (MIF) fractionations of Hg isotopes are caused by a wide variety of biogeochemical processes including redox reactions and volatilization. Volcanic activities and its associated hydrothermal activities are the main sources of naturally-emitted Hg in the environment. Several previous studies suggested that the naturally-emitted Hg indicated both MDF and MIF. It was thought that the MDF was caused by a process of liquid-vapor partitioning during ascending and the MIF was caused by photoreduction. It was, however, suggested that both photoreduction and volatilization could cause the MIF, and it has never been distinguish from each other in the hydrothermal systems. In this study, geological samples in active deep-sea hydrothermal systems at Izu-Bonin arc were collected and measured their Hg isotopic compositions. They indicate both MDF and MIF. The δ202Hg values range from -1.0 to 0.5 ‰, indicating the liquid-vapor partitioning, whereas the calculated Δ199Hg values are mostly between 0.1 and 0.2‰, indicating the MIF in the deep-sea hydrothermal systems without photoreduction. The linear relationship between Δ199Hg and Δ201Hg, ranging from 1.6 and 2.0, also indicates the nuclear volume effect. This result suggest that MDF and MIF of Hg isotopic compositions can be utilized to distinguish naturally-emitted Hg from anthropogenic Hg.