Isotopic composition of dissolved inorganic carbon in subsurface sediments of gas hydrate-bearing mud volcanoes, Lake Baikal: implications for methane and carbonate origin

• Published in: Geo-marine letters Vol. 30; no. 3-4; pp. 427 - 437
• Main Authors: Krylov, Alexey A., Khlystov, Oleg M., Hachikubo, Akihiro, Minami, Hirotsugu, Nunokawa, Yutaka, Shoji, Hitoshi, Zemskaya, Tamara I., Naudts, Lieven, Pogodaeva, Tatyana V., Kida, Masato, Kalmychkov, Gennady V., Poort, Jeffrey
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2010; Springer Nature B.V; Springer Verlag
• Subjects: Carbon; Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Isotopes; Methane; Original; Samples; Sciences of the Universe; Lake Baikal; Russia, Siberia, Baykal L; Southern Basin; Dissolve Inorganic Carbon; Methane Hydrate; Isotopic Composition; Siderite
• ISSN: 0276-0460; 1432-1157
• DOI: 10.1007/s00367-010-0190-2

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 δ 13 C values of DIC become heavier with increasing subbottom depth, and vary between −9.5 and +21.4‰ PDB. Enrichment of DIC in 13 C 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 CO 2 -reduction) were revealed by determining the offset of δ 13 C between dissolved CH 4 and CO 2 , and also by using δ 13 C 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.