U.S. Dept. of Commerce / NOAA / OAR / PMEL / Publications
Hydrothermal plumes formed by mixing of seafloor vent fluids and ambient seawater
are easily detectable by physical and chemical tracers. New in situ instrumentation
is providing the capability of continuous measurement of certain chemical species
(e.g., dissolved Mn and Fe) to complement the continuous measurement of hydrographic
and optical tracers. Hydrothermal plume evidence of seafloor venting has been
recognized for over 30 years, though only in the last decade have systematic
surveys been conducted. Most detailed surveys have been conducted along medium-
to superfast-spreading eastern Pacific spreading centers because the narrow
crest of these ridges permits a largely two-dimensional mapping effort. Carefully
studied areas include the Juan de Fuca Ridge (44°30'-48°30'N) and 9°-13°N and
13°40'-18°40'S on the East Pacific Rise. Plumes have been detected in several
western Pacific marginal basins, but only parts of the North Fiji (15°-20°S)
and Manus Basins have been surveyed in detail. In the North Atlantic, plume
surveys have visited a longer length of ridge than in the Pacific, but surveys
typically have been less detailed because of the wide and deep axial valleys.
Work along the Reykjanes Ridge (58°-63°N) and the Mid-Atlantic Ridge (11°-40°N)
indicates a lower incidence of venting than in the Pacific. Plumes have been
sampled near the Rodriguez Triple Junction in the Indian Ocean, but no systematic
mapping has been accomplished there. About 10% of the
Two primary conclusions are apparent from this review. First, careful plume surveys can efficiently locate seafloor discharge sites to within a few kilometers or less. Plume mapping can substantially diminish the search time required to locate vents precisely by submersible or remote imagery, and should normally precede seafloor exploration efforts to improve their efficiency. Second, while seafloor venting occurs on ridge segments of spreading rates from slow to superfast, hydrothermal plume production along any multisegment ridge portion is directly related to the spreading rate.
Acknowledgments. This review was supported by the NOAA VENTS Program (ETB), by IOSDL and NERC grant BRIDGE 15 (CRG), and by NERC grant GR3/8596 and a grant from the NERC BRIDGE Program (HE). The impetus for this paper was discussions at the 1993 RIDGE Theoretical Institute at Big Sky, MT, USA. We thank the conveners and participants for channeling our energies into this effort. Cambridge Earth Sciences contribution number ES 4086. IOSDL contribution number 95003. PMEL contribution number 1538.
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