Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS21] Gas hydrate in environmental-resource sciences

Tue. May 28, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Akihiro Hachikubo(Kitami Institute of Technology), Atsushi Tani(Graduate School of Human Development and Environment, Kobe University), Shusaku Goto(Institute for Geo-Resources and Environment National Institute of Advanced Industrial Science and Technology)

[MIS21-P07] Carbon isotope fractionation of CO2 during the formation of clathrate hydrate

*Hiromi Kimura1, Jumpei Matsuda1, Yuki Kikuchi1, Akihiro Hachikubo1, Satoshi Takeya2 (1.Kitami Institute of Technology, 2.National Institute of Advanced Industrial Science and Technology)

Keywords:gas hydrate, stable isotope, carbon dioxide, isotopic fractionation

Hydrogen Isotope fractionation in methane during the formation of clathrate hydrate was reported by Hachikubo et al. (2007) that δD of hydrate-bound methane is 4.8±0.4‰ lower than that of residual methane at 274.2K. Although natural methane hydrates distribute widely in the world, natural CO2 hydrate was only reported at the Okinawa Trough (Sakai et al., 1990). It is also possible that CO2 hydrate exists in Mars. Isotopic fractionation of guest gas may provide useful information to understand formation processes of gas hydrate. Luzi et al. (2011) revealed that CO2 δ13C in hydrate-bound gas is 0.9‰ lower than that of residual gas, suggesting that light CO2 molecules prefer to be encaged into clathrate cages. In this study, we checked the temperature effect on the isotopic difference between residual and hydrate-bound CO2.

Samples of CO2 hydrate (weight: 0.7 g) were experimentally prepared in a pressure cell (volume: 30 mL), and the temperature was controlled by a liquid bath (258-274 K) and cold rooms (226-254 K). Isotopic compositions of both residual and hydrate-bound CO2 were measured by an isotope ratio mass spectrometer (IRMS). Samples were formed in the temperature range from 226 K to 274 K. The carbon isotopic differences between hydrate-bound and residual CO2 distributed between 1.2‰ and 1.5‰, agreed fairly well with the previous report (Luzi et al., 2011). The difference seemed to be large (1.5-2.0 ‰) at 226 K, indicating that the equilibrium pressure of 13CO2 hydrate is slightly larger than that of 12CO2 hydrate, and the difference between them becomes large in lower temperature. We will show these equilibrium data for 13CO2 and 12CO2 hydrates and compare with the results in stable isotope.


Hachikubo A, Kosaka T, Kida M, Krylov A, Sakagami H, Minami H, Takahashi N, Shoji H (2007) Isotopic fractionation of methane and ethane hydrates between gas and hydrate phases. Geophys Res Lett 34: L21502. doi:10.1029/2007GL030557

Sakai H, Gamo T, Kim ES, Tsutsumi M, Tanaka T, Ishibashi J, Wakita H, Yamano M, Oomori T (1990) Venting of carbon dioxide-rich fluid and hydrate formation in mid-okinawa trough backarc basin. Science: 248, 4959, 1093-1096.

Luzi M, Schicks JM, Erzinger J (2011) Carbon isotopic fractionation of synthetic methane and carbon dioxide hydrates. Proc. 7th International Conference on Gas Hydrates (ICGH2011).