11:15 〜 11:30
[MIS24-14] バイカル湖中央湖盆北部の天然ガスハイドレートの特徴
キーワード：ガスハイドレート, 結晶構造, バイカル湖
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.
Bernard BB, Brooks JM, Sackett WM (1976) Natural gas seepage in the Gulf of Mexico. Earth Planet Sci Lett 31: 48-54.
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
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.
Bernard BB, Brooks JM, Sackett WM (1976) Natural gas seepage in the Gulf of Mexico. Earth Planet Sci Lett 31: 48-54.
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