Other
Scientific paper
Oct 1980
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980e%26psl..50..115l&link_type=abstract
Earth and Planetary Science Letters, Volume 50, Issue 1, p. 115-127.
Other
19
Scientific paper
Water samples collected at the 21°N hydrothermal site on the East Pacific Rise crest, including Deep-Tow and hydrocast samples collected in 1977 and three hot vent water samples collected recently with the submersible ``Alvin'', contain significant additions of 3He, 4He, and Mn. Although the vent water collections were at least 50-fold diluted with ambient seawater, they are up to 53 times enriched in 3He and 7.4 times enriched in 4He relative to saturated seawater, with concentrations of total dissolvable manganese (TDM) up to 310 μg/kg. 3He and 4He covary in the vent samples, with 3He/4He about 8 times the atmospheric ratio, reflecting a mantle helium source. In contrast to the helium isotopes the Mn/3He ratio in the vent samples is variable, ranging from 4.3 × 104 up to 1.0 × 105 g/cm3. Profiles of 3He/4He and TDM in the water column at 21°N show a sharp maximum of δ(3He) = 47% and TDM = 0.69 μg/kg, much higher than the average values of 34% and 0.2 μg/kg for the deep water in this region. This spike in 3He and Mn occurs at 2400 m depth, 200 m above the level of the 21°N vents, and 100 m higher than any local bathymetry, evidence for upward transport of the hydrothermal discharge via rising plumes of hot vent water. Two of the 21°N Deep-Tow samples associated with small (<=0.010°C) temperature anomalies had δ(3He) = 38% and TDM = 0.28 and 0.58 μg/kg, also slightly elevated relative to background. The Deep-Tow and hydrocast samples have lower Mn/3He ratios than average vent samples due to Mn removal by scavenging. Comparison of vent samples and water column measurements at 21°N indicate that the pure vent water could be detected using 3He and Mn even when diluted ~105 times with seawater, confirming that these two tracers are extremely sensitive indicators of submarine hydrothermal activity.
Craig Harmon
Haymon Rachel
Klinkhammer Gary P.
Lupton John. E.
MacDonald Ken C.
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