Fluid migrations at the Krasny Yar methane seep of Lake Baikal according to geochemical data

Abstract

Sediments of the deep water Krasny Yar methane seep area of Lake Baikal contain channels of 1 cm in diameter and up to a depth of 150 cm that have a high water content and are characterized by higher oxidized and reduced conditions than the surrounding sediment. New data of lithological and geochemical studies, including the full anionic and cationic composition of pore waters, indicate that chemical flow at the sediment surface of the seep is heterogeneous in space with both areas of inflow of fluids and areas with outflow of fluids. We suggest that much of this flow is modulated by more complex hydrological processes that may include aqueous pumping driven by gas expulsion- and changes in the permeability of the conduits due to gas hydrate formation and dissociation. We discuss the seep output fluid chemistry and heat flow in relation to the above hydrological processes and propose a seep model where fluid and gas migrations act at different spatial scales partly favored by hydrate accumulation and the fresh water conditions of Lake Baikal.