Testing short-range migration of microbial methane as a hydrate formation mechanism: Results from Andaman Sea and Kumano Basin drill sites and global implications

摘要: Abstract Methane gas hydrates in marine sediments often concentrate coarse-grained layers surrounded by fine-grained muds that are hydrate-free. these hydrate deposits is typically microbial, and must have migrated from its source as the contain little or no organic matter. In “long-range” migration, fluid flow through permeable transports methane deeper sources into stability zone (GHSZ). “short-range” microbial generated within GHSZ sediments, where small pore sizes inhibit formation. Dissolved can then diffuse adjacent sand layers, size does not restrict formation accumulate. Short-range migration has been used to explain accumulations observed drill sites on northern Cascadia margin Gulf of Mexico. Here we test feasibility short-range two additional locations, found volcanic ash (Site NGHP-01-17, Andaman Sea, Indian Ocean) turbidite beds IODP-C0002, Kumano forearc basin, Nankai Trough, western Pacific). We apply reaction–transport modeling calculate dissolved concentration amounts resulting GHSZ. Model results show overall at sites. shown be feasible diverse environments likely a widespread transport mechanism systems. It only requires amount carbon sediment sequences consisting thin thick beds; conditions common along continental margins around globe.