Molecular and isotopic characteristics of gas hydrate-bound hydrocarbons in southern and central Lake Baikal

作者：Hachikubo Akihiro^*; Khlystov Oleg; Krylov Alexey; Sakagami Hirotoshi; Minami Hirotsugu; Nunokawa Yutaka; Yamashita Satoshi; Takahashi Nobuo; Shoji Hitoshi; Nishio Shin'ya; Kida Masato; Ebinuma Takao; Kalmychkov Gennadiy; Poort Jeffrey

来源：Geo-Marine Letters, 2010, 30(3-4): 321-329.

DOI：10.1007/s00367-010-0203-1

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 (delta(13)C and delta D) 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 delta(13)C signatures at two sites where ethane delta(13)C 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 (13)C and deuterium were both highly depleted (mean delta(13)C and delta D of -61.6aEuro degrees V-PDB and -285.4aEuro degrees V-SMOW, respectively). To the best of our knowledge, this is the first report of C(2) delta(13)C-delta D classification for hydrate-bound gas in either freshwater or marine environments.

• 出版日期2010-6