Hydrothermal plumes over spreading ridges and related deposits in the northeast Pacific Ocean: The East Pacific Rise near 11 degrees north and 21 degrees north, Explorer Ridge and J. Tuzo Wilson Seamounts

Hydrothermal plumes emanating from hot springs over spreading ridges in the north east Pacific Ocean have been mapped and sampled using the submersible ALVIN and equipment deployed from surface ships. The geologic setting and polymetallic sulfides of the vent field producing the hydrothermal plume at 11;No unambiguous chemical or physical signatures of hydrothermal plumes were found in the Northern Explorer Ridge-Basins 1 and 2. However, there is fragmentary evidence for hydrothermal venting at J. Tuzo Wilson Seamounts. Two hydrothermal plumes originating from sources 1.2 km apart were detected by light scattering sensors and geochemistry over Southern Explorer Ridge. A diffuse layer (average thickness of 50 m) of lower particulate concentration is present below the plume and may be due either to fallout from the plume or to local, low temperature 'leaky' venting, or both. One plume, from Magic Mountain, was neutrally-buoyant and the other was well-focused and rising. The latter plume, from the AGOR 171 vent site, is characterized by Fe-rich (27 wt %) colloidal-sized, x-ray amorphous oxyhydroxides which is among the most Fe-rich non-sulfide suspended material collected to date. (Abstract shortened with permission of author.).