|A reassessment of gas hydrate occurrences in Lake Baikal|
De Batist, M.; Klerkx, J.; Naudts, L.; Poort, J.; Khlystov, O.; Golmshtok, A. Y. ; Kremlev, A. N. ; Duchkov, A. D.; Granin, N. (2007). A reassessment of gas hydrate occurrences in Lake Baikal. Eos, Trans. (Wash. D.C.) 88(52): OS23A-1053
In: Eos, Transactions, American Geophysical Union. American Geophysical Union: Washington. ISSN 0096-3941; e-ISSN 2324-9250
MARINE GEOLOGY AND GEOPHYSICS; Gas and hydrate systems; Marine seismics
|Auteurs|| || Top |
- De Batist, M.
- Klerkx, J.
- Naudts, L.
- Poort, J.
- Khlystov, O.
- Golmshtok, A. Y.
- Kremlev, A. N.
- Duchkov, A. D.
- Granin, N.
Lake Baikal is the only fresh-water lake with gas hydrates in its sedimentary fill (i.e., in a non-marine, non- permafrost setting). The hydrates have been sampled in deep boreholes and in short cores, and consist in most cases of nearly-pure methane sI hydrate of biogenic origin, although locally - in specific settings - sII hydrates have been observed as well. The extent of the deep hydrates was mapped by tracing the Bottom-Simulating Reflector on MCS profiles: they are present in large parts of the southern and central Baikal basins, at water depths of > 360 m. In several places, clusters of mud volcanoes occur in this hydrate province. They all occur in within the Gas- Hydrate Stability Zone and in the immediate vicinity of major, active faults. The mud volcanoes have dimensions of 250-1600 m in diameter and of 15-220 m in height; they are characterized by mud breccias and the extensive occurrence of near-bottom hydrates. Methane, fluid and mud release from these edifices is not continuous and most are dormant at present. The methane and associated fluids in some of them are believed to originate from destabilizing gas hydrates at 200-300 m sub-bottom depth under the influence of a tectonically controlled geothermal fluid pulse along adjacent faults, but this appears not to be the case for all. In addition, several active methane vents have recently been discovered, both in deep (> 800 m) and in shallow (< 230 m) water. Deep-water seeps occur outside the mud-volcano regions, and most of them outside the hydrate province; shallow-water seeps occur on the upper slopes of the basin, mostly in the vicinity of deltas, slope canyons or faults, and bubbles escaping from them often reach the lake surface. Methane release appears to be more continuous and bubbles can often be observed to reach the lake surface. INTAS Projects 1945 and 2309 have investigated these gas hydrates and gas seeps, as well as the consequences of the methane expulsion from mud volcanoes and shallow seeps for the waters of Lake Baikal, and has been monitoring mud volcano and seep activity over a period of 2 years.