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Isotopic composition of dissolved inorganic carbon in subsurface sediments of gas hydrate-bearing mud volcanoes, Lake Baikal: implications for methane and carbonate origin |
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| Authors: | Alexey A Krylov Oleg M Khlystov Akihiro Hachikubo Hirotsugu Minami Yutaka Nunokawa Hitoshi Shoji Tamara I Zemskaya Lieven Naudts Tatyana V Pogodaeva Masato Kida Gennady V Kalmychkov Jeffrey Poort |
| Institution: | 1. I.S. Gramberg All-Russia Research Institute for Geology and Mineral Resources of the World Ocean (VNIIOkeangeologia), 1 Anglyisky Ave., St. Petersburg, 190121, Russia 2. Limnological Institute, Siberian Branch of Russian Academy of Science, 3 Ulan-Batorskaya St., Irkutsk, 664033, Russia 3. Kitami Institute of Technology, 165 Koen-cho, Kitami, 090-8507, Japan 4. Renard Centre of Marine Geology, Ghent University, Krijgslaan 281 s8, 9000, Ghent, Belgium 5. National Institute of Advanced Industrial Science and Technology, 2-17-2-1 Tsukisamu-Higashi, Toyohira-ku, Sapporo, 062-8517, Japan 6. A.P. Vinogradov Institute of Geochemistry, Siberian Branch of Russian Academy of Science, 1-a Favorsky St., Irkutsk, 664033, Russia 7. Laboratoire de Géosciences Marines, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005, France |
| Abstract: | We report on the isotopic composition of dissolved inorganic carbon (DIC) in pore-water samples recovered by gravity coring from near-bottom sediments at gas hydrate-bearing mud volcanoes/gas flares (Malenky, Peschanka, Peschanka 2, Goloustnoe, and Irkutsk) in the Southern Basin of Lake Baikal. The δ13C values of DIC become heavier with increasing subbottom depth, and vary between ?9.5 and +21.4‰ PDB. Enrichment of DIC in 13C indicates active methane generation in anaerobic environments near the lake bottom. These data confirm our previous assumption that crystallization of carbonates (siderites) in subsurface sediments is a result of methane generation. Types of methanogenesis (microbial methyl-type fermentation versus CO2-reduction) were revealed by determining the offset of δ13C between dissolved CH4 and CO2, and also by using δ13C and δD values of dissolved methane present in the pore waters. Results show that both mechanisms are most likely responsible for methane generation at the investigated locations. |
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