Gas hydrate accumulation in the subsurface sediments of Lake Baikal (Eastern Siberia)

Gas hydrate (GH) accumulation in subsurface sediments was discovered at shallow depth within the Malenkiy vent structure in the southern basin of Lake Baikal. The hydrated gas consists mainly of methane. Interstitial water chemistry indicates that water discharged within the study area is enriched with salts, especially Ca, Cl, and SO4 ions. The ascending water delivering gas into the GH stability zone is thought to be the main GH-forming fluid. Geochemical data together with noble gas isotopic ratios suggest that the GH in the subsurface sediments of Lake Baikal originated from a deep source of water with anomalous composition assumed to be derived from buried paleolakes. As a whole, the GH accumulation corresponds to the area of the Malenkiy structure and is represented by several small-scale GH occurrences coincident with local fluid discharge manifestations. It is filtrational in origin, related to fluid flow features and controlled by tectonic setting.