Japan Geoscience Union Meeting 2015

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS24] Gas hydrates in environmental-resource sciences

Thu. May 28, 2015 11:00 AM - 12:45 PM 102B (1F)

Convener:*Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Akihiro Hachikubo(Environmental and Energy Resources Research Center, Kitami Institute of Technology), Sumito Morita(Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology), Chair:Atsushi Tani(Graduate School of Science, Osaka University)

11:15 AM - 11:30 AM

[MIS24-14] Characteristics of natural gas hydrate retrieved at northern central Baikal basin

*Akihiro HACHIKUBO1, Oleg KHLYSTOV2, Gennadiy KALMYCHKOV3, Hirotoshi SAKAGAMI1, Hirotsugu MINAMI1, Satoshi YAMASHITA1, Nobuo TAKAHASHI1, Hitoshi SHOJI1, BATIST, Marc DE4 (1.Kitami Institute of Technology, 2.Limnological Institute, SB RAS, 3.Vinogradov Institute of Geochemistry, SB RAS, 4.Ghent University)

Keywords:gas hydrate, crystallographic structure, Lake Baikal

Lake Baikal (Russia) is the solitary example of hydrate-bearing area in the environment of fresh water. Gas hydrate samples in sandy turbidites were first obtained at the southern Baikal basin in the Baikal Drilling Project in 1997. Multi-phase Gas Hydrate Project (MHP, 2009-2014), the international collaboration between Japan, Russia, and Belgium, has revealed distribution of gas hydrate in sub-bottom sediment at the southern and central Baikal basins. In the last cruise (MHP-14) we obtained gas hydrate crystals from four new places (Kukuy K-5, Khoboy, Akadem Ridge, and Barguzin) at the central Baikal basin. We report the characteristics of hydrate-bound gases at these sites.
Samples of hydrate-bound gas were obtained onboard and stored in 5-mL vials. We measured molecular and stable isotope compositions of the samples. According to the C1/C2 - C1δ13C diagram (Bernard et al., 1976), the δ13C-δD diagram for C1 (Whiticar, 1999), and the C1δ13C - C2δ13C diagram (Milkov, 2005), the gas characteristics show the following information:

1) Hydrocarbons at the Khoboy, Akadem Ridge, and Barguzin are microbial origin, and those of Kukuy K-5 is in the field of mixed-gas between microbial and thermogenic gases.

2) In the "Bernard diagram", hydrate-bound hydrocarbons of Kukuy K-5 locate on the mixing line of microbial gas at the Kukuy K-9 and thermogenic gas at the Kukuy K-4, those are the end members at the Kukuy Canyon area.

3) C2 δ13C of the hydrate-bound gas at the the Khoboy, Akadem Ridge, and Barguzin are low (less than -50‰), indicating microbial C2. Microbial C2 in the hydrate-bound gas has been observed at the Krasnyi Yar and Peschanka P-2 at the southern Baikal basin, and the Ukhan and Unshuy at the central Baikal basin.

4) The site Barguzin locates only 7 km distance from the site Gorevoy Utes, where oil-stained gas hydrate with thermogenic gas was retrieved.

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Milkov AV (2005) Molecular and stable isotope compositions of natural gas hydrates: a revised global dataset and basic interpretations in the context of geological settings. Org Geochem 36: 681-70. doi:10.1016/j.orggeochem.2005.01.010

Whiticar MJ (1999) Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane. Chem Geol 161: 291-314. doi:10.1016/S0009-2541(99)00092-3