Methane, helium isotope and hydrogen data from the Nibelungen hydrothermal area, Mid Atlantic Ridge


Hydrothermal emission of mantle helium appears to be directly related to magma production rate, but other processes can generate methane and hydrogen on mid-ocean ridges. In an on-going effort to characterize these processes in the South Atlantic, the flux and distribution of these gases were investigated in the vicinity of a powerful black smoker recently discovered at 8°17.9' S, 13°30.4' W. The vent lies on the shoulder of an oblique offset in the Mid-Atlantic Ridge and discharges high concentrations of methane and hydrogen. Measurements during expeditions in 2004 and 2006 show that the ratio of CH4 to 3He in the neutrally buoyant plume is quite high, 4 x 10**8. The CTD stations were accompanied by velocity measurements with lowered acoustic Doppler current profilers (LADCP), and from these data we estimate the methane transport to have been 0.5 mol/sec in a WSW-trending plume that seems to develop during the ebb tidal phase. This transport is an order of magnitude greater than the source of CH4 calculated from its concentration in the vent fluid and the rise height of the plume. From this range of methane fluxes, the source of 3He is estimated to be between 0.14 and 1.2 nmol/sec. In either case, the 3He source is significantly lower than expected from the spreading rate of the Mid-Atlantic Ridge. From the inventory of methane in the rift valley adjacent to the vent, it appears that the average specific rate of oxidation is 2.6 to 23/yr, corresponding to a turnover time between 140 and 16 days. Vertical profiles of methane in the surrounding region often exhibited Gaussian-like distributions, and the variances appear to increase with distance from the vent. Using a Gaussian plume model, we obtained a range of vertical eddy diffusivities between 0.009 and 0.08 m2m2/sec. These high values may be due to tidally driven internal waves across the promontory on which the vent is located.

Supplement to: Keir, Robin; Schmale, Oliver; Walter, Maren; Sültenfuß, Jürgen; Seifert, Richard; Rhein, Monika (2008): Flux and dispersion of gases from the "Drachenschlund" hydrothermal vent at 8°18'S, 13°30'W on the Mid-Atlantic Ridge. Earth and Planetary Science Letters, 270, 338-348

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Metadata Access
Creator Keir, Robin; Schmale, Oliver; Walter, Maren; Sültenfuß, Jürgen ; Seifert, Richard; Rhein, Monika
Publisher PANGAEA
Publication Year 2008
Funding Reference German Science Foundation, 5471797
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Language English
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 53 datasets
Discipline Earth System Research
Spatial Coverage (-13.635W, -8.345S, -13.452E, -8.167N); South Atlantic/subtropical
Temporal Coverage Begin 2004-11-29T00:00:00Z
Temporal Coverage End 2006-05-25T10:03:00Z