Molecular and isotopic characteristics of gas hydrate-bound hydrocarbons in southern and central Lake Baikal
Hachikubo, A.; Khlystov, O.; Krylov, A.; Sakagami, H.; Minami, H.; Nunokawa, Y.; Yamashita, S.; Takahashi, N.; Shoji, H.; Nishio, S.; Kida, M.; Ebinuma, T.; Kalmychkov, G.; Poort, J. (2010). Molecular and isotopic characteristics of gas hydrate-bound hydrocarbons in southern and central Lake Baikal. Geo-Mar. Lett. 30(3-4): 321-329. dx.doi.org/10.1007/s00367-010-0203-1 In: Geo-Marine Letters. Springer: Heidelberg; Berlin. ISSN 0276-0460; e-ISSN 1432-1157, more |  |
| Authors | | Top | - Hachikubo, A.
- Khlystov, O.
- Krylov, A.
- Sakagami, H.
- Minami, H.
| - Nunokawa, Y.
- Yamashita, S.
- Takahashi, N.
- Shoji, H.
- Nishio, S.
| - Kida, M.
- Ebinuma, T.
- Kalmychkov, G.
- Poort, J., more
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| Abstract | We investigated the molecular composition (methane, ethane, and propane) and stable isotope composition (methane and ethane) of hydrate-bound gas in sediments of Lake Baikal. Hydrate-bearing sediment cores were retrieved from eight gas seep sites, located in the southern and central Baikal basins. Empirical classification of the methane stable isotopes (d13C and dD) for all the seep sites indicated the dominant microbial origin of methane via methyl-type fermentation; however, a mixture of thermogenic and microbial gases resulted in relatively high methane d13C signatures at two sites where ethane d13C indicated a typical thermogenic origin. At one of the sites in the southern Baikal basin, we found gas hydrates of enclathrated microbial ethane in which 13C and deuterium were both highly depleted (mean d13C and dD of –61.6‰ V-PDB and –285.4‰ V-SMOW, respectively). To the best of our knowledge, this is the first report of C2 d13C–dD classification for hydrate-bound gas in either freshwater or marine environments. |
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