Water column hydrothermal plumes on the Juan de Fuca Ridge

Journal Article · Fri Aug 10 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB08p12829· OSTI ID:5138293

Lupton, J E ^[1]

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1. Univ. of California, Santa Barbara (United States)

Hydrographic surveys on the Juan de Fuca Ridge (JdFR) carried out from 1980 to 1987 show a complex pattern of {sup 3}He and Mn-rich water column plumes produced by venting from several submarine hot spring areas. In the vicinity of Axial Volcano at latitude 46{degree}N, distinct plumes were detected in 1980, 1982, and 1983 with {sup 3}He signatures up to {delta}({sup 3}He) = 64% at {approximately} 1,500 m depth at distances of {approximately} 10 km from the seamount summit. However, the same plumes had no detectable thermal signature, a paradox which is attributed to the high {sup 3}He/heat ratios and low salinities of the fluids venting within the caldera of Axial Volcano. Profiles directly over the seamount show hydrothermal {sup 3}He in the water column up to 300 m above the caldera floor, with the {sup 3}He signal increasing with depth to very high and uniform ratios of {delta}({sup 3}He) = 108-150% below the {approximately} 1,500-m caldera sill depth. Another apparent locus of hydrothermal input is Helium Basin, a depression on the northeast flank of Axial Volcano which had {delta}({sup 3}He) = 51% when first sampled in 1980. However, subsequent hydrocasts into Helium Basin in 1982 and 1983 yielded lower helium enrichments, suggesting either a decrease in hydrothermal input or flushing of the basin via a mixing event. To the south of Axial Volcano, high {delta}({sup 3}He) values of {approximately} 40% observed over the ridge axis at 45{degree}18{prime}N and 45{degree}39{prime}N indicate venting on this previously unexplored section of the ridge. The water column plumes over the US Geological Survey vent site at {approximately} 44{degree}40{prime}N on the southern JdFR have very high Mn/{sup 3}He ratios of 4,600 mol/cm{sup 3}, an apparently unique characteristic which can be used to distinguish these plumes from those originating at other JdFR vent fields.

• OSTI ID: 5138293
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B8; ISSN JGREA; ISSN 0148-0227
• Country of Publication: United States
• Language: English

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15 GEOTHERMAL ENERGY
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GEOCHEMISTRY
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GEOPHYSICS
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HELIUM 3
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