Mass wasting, ephemeral fluid flow, and barite deposition on the California continental margin

An area of active fluid discharge characterized by authigenic barite format ion and populated by vestimentiferan tubeworms has been discovered by remot ely operated vehicle exploration in Monterey Canyon, Slumping and mass wast ing, presumably triggered by seismic activity, have exposed barium-rich por e fluids to sulfate-rich bottom water, leading to barite precipitation on t he sea floor. Age estimates based on (210)pb/Ra-226 dating of the barite sa mples and growth rates of vestimentiferan tubeworms indicate that the seep site might be as young as 100 yr. Systematic variations in sulfur and stron tium isotope ratios, the lack of visible fluid now, and the abundance of de ad tubeworms indicate decreasing flow rates. This newly discovered site sho ws many similarities to a previously described barite deposit in the Califo rnia Borderland, possibly misinterpreted as a hydrothermal vent site, The d iscovery of a cold seep associated with barite deposits on the seismically active, transpressional California margin raises the possibility that numer ous unexplored areas along the continental margins might have similar low-t emperature deposits.