Contribution of cold seep barite to the barium geochemical budget of a marginal basin

We investigated barium partitioning in a marginal basin where large barite structures occur associated with cold seeps on the San Clemente fault, off the coast of southern California. The barium flux to San Clemente basin sediments is two to three times greater than fluxes measured in surrounding California Borderland basins where there is no evidence of seeps. Barium is accumulating in San Clemente sediments at an average rate of approximately 11 μmol m−2 day−1. Analyses of sediment trap material, water column samples, sediments and pore water indicate that expected barium-bearing mineral phases (e.g. detrital aluminosilicates, biogenic material and Fe/Mn oxyhydroxides) cannot account for all the barium accumulating in the San Clemente Basin. The excess barium, which represents transport of cold seep barite, is comparable to the combined flux of detrital and biogenic material to the basin floor. The magnitude of this flux and the occurrence of cold seeps throughout the oceans necessitate consideration of this phase in the development of barium geochemical budgets and the variety of paleoproxies involving barium in marine sediments.