Flux and dispersion of gases from the “Drachenschlund” hydrothermal vent at 8°18' S, 13°30' W on the Mid-Atlantic Ridge

Keir, Robin S.; Schmale, Oliver; Walter, Maren; Sültenfuß, Jürgen; Seifert, Richard; Rhein, Monika

doi:10.1016/j.epsl.2008.03.054

Cited by 85 publications

(31 citation statements)

References 43 publications

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“…Such high CH 4 / 3 He ratios may be a characteristic of ultramafic hosted hydrothermal vents. The plume from the “Drachenschlund” at 8° 18′S on the MAR, another high‐temperature vent affected by serpentinization, indicates a CH 4 / 3 He ratio of about 4 × 10 8 [ Keir et al , 2008].…”

Section: Ch4 Versus δ3hementioning

confidence: 99%

“…This is a guess at what may be a crude analog of dispersion in the presence of tidally varying currents. Lateral dispersion of the methane plume from the Drachenschlund vent appeared to be in the range of 2–20 m 2 s −1 [ Keir et al , 2008]. The K x we employ in the model is greater than what one might expect in the surface ocean, where horizontal eddy diffusion appears to be dependent on the length scale of mixing [ Joseph and Sendner , 1958].…”

Section: Model Parameterizationmentioning

confidence: 99%

“…They suggested that a population of methane‐oxidizing bacteria develops in the plume and influences the oxidation rate. Estimates of the average specific rate in other methane plumes range from 0.002 to 0.01 day −1 [ Tsunogai et al , 2000; Valentine et al , 2001; Keir et al , 2008]. In newly formed deep waters, the turnover time appears to be much longer, on the order of decades [ Rehder et al , 1999; Heeschen et al , 2004; Keir et al , 2005].…”

Section: Introductionmentioning

confidence: 99%

“…Diamonds indicate locations of methane plumes for which the source has not been identified. Adjacent numbers indicate δ 13 C of methane in the vent fluids/plumes (compiled by Charlou et al [2002]; also Keir et al [2005, 2008]). Squares show locations of off‐axis GEOSECS and Merian 4/3 stations.…”

Section: Introductionmentioning

confidence: 99%

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Isotope fractionation and mixing in methane plumes from the Logatchev hydrothermal field

Keir

Schmale

Seifert

et al. 2009

Geochem Geophys Geosyst

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[1] As methane is consumed in the deep sea, its 13 C/ 12 C ratio progressively increases because of kinetic isotope fractionation. Many submarine hydrothermal vents emit methane with carbon isotope ratios that are higher than those of background methane in the surrounding ocean. Since the latter exists at low concentrations, mixing of background methane with vent fluid tends to decrease the 13 C/ 12 C ratio as concentration decreases, opposite to the trend produced by consumption. We investigated CH 4 concentration and d 13 C together with d 3 He in plumes from the Logatchev hydrothermal field (LHF) located at 14°45 0 N, 45°W, which generates relatively heavy methane (d 13 C % À13%) by serpentinization of ultramafic rock. The measured methane and d 3 He were well correlated at high concentrations, indicating a CH 4 / 3 He ratio of 1 Â 10 8 in the vent fluids. These tracer distributions were also simulated with an advection-diffusion model in which methane consumption only occurs above a certain threshold concentration. We utilized d 3 He to calculate the methane remaining in solution after oxidation, f, and the deviation of d 13 C from the value expected from mixing alone, Dd 13 C. Both in the model and in the data, the entire set of Dd 13 C values are not correlated with log f, which is due to continuous oxidation within the plume while mixing with background seawater. A linear relationship, however, is found in the model for methane at concentrations sufficiently above background, and many of the samples with elevated CH 4 north of LHF exhibit a linear trend of Dd 13 C versus log f as well. From this trend, the kinetic isotope fractionation factor in the LHF plumes appears to be about 1.015. This value is somewhat higher than found in some other deep-sea studies, but it is lower than found in laboratory incubation experiments.

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Section: Ch4 Versus δ3hementioning

confidence: 99%

Section: Model Parameterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isotope fractionation and mixing in methane plumes from the Logatchev hydrothermal field

Keir

Schmale

Seifert

et al. 2009

Geochem Geophys Geosyst

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“…It is generated in terrestrial, limnic and marine ecosystems by biotic (Segers, 1998;Reeburgh, 2007) and abiotic mechanisms (Berndt et al, 1996;Keir et al, 2008). Although methane is trapped in aquatic sediments in vast amounts, marine environments only represent a negligible source for atmospheric methane (Reeburgh, 2007).…”

Section: Introductionmentioning

confidence: 99%

Comparative studies of pelagic microbial methane oxidation within the redox zones of the Gotland Deep and Landsort Deep (central Baltic Sea)

et al. 2013

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Abstract. Pelagic methane oxidation was investigated in dependence on differing hydrographic conditions within the redox zone of the Gotland Deep (GD) and Landsort Deep (LD), central Baltic Sea. The redox zone of both deeps, which indicates the transition between oxic and anoxic conditions, was characterized by a pronounced methane concentration gradient between the deep water (GD: 1233 nM, 223 m; LD: 2935 nM, 422 m) and the surface water (GD and LD < 10 nM). This gradient together with a 13 C CH 4 enrichment (δ 13 C CH 4 deep water: GD −84 ‰, LD −71 ‰; redox zone: GD −60 ‰, LD −20 ‰; surface water: GD −47 ‰, LD −50 ‰; δ 13 C CH 4 vs. Vienna Pee Dee Belemnite standard), clearly indicating microbial methane consumption within the redox zone. Expression analysis of the methane monooxygenase identified one active type I methanotrophic bacterium in both redox zones. In contrast, the turnover of methane within the redox zones showed strong differences between the two basins (GD: max. 0.12 nM d −1 , LD: max. 0.61 nM d −1 ), with a nearly four-times-lower turnover time of methane in the LD (GD: 455 d, LD: 127 d). Vertical mixing rates for both deeps were calculated on the base of the methane concentration profile and the consumption of methane in the redox zone (GD: 2.5 × 10 −6 m 2 s −1 , LD: 1.6 × 10 −5 m 2 s −1 ). Our study identified vertical transport of methane from the deep-water body towards the redox zone as well as differing hydrographic conditions (lateral intrusions and vertical mixing) within the redox zone of these deeps as major factors that determine the pelagic methane oxidation.

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Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule earthquake, Central Chile

Geersen

Scholz

Линке

et al. 2016

Geochem Geophys Geosyst

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Seafloor seepage of hydrocarbon-bearing fluids has been identified in a number of marine fore arcs. However, temporal variations in seep activity and the structural and tectonic parameters that control the seepage often remain poorly constrained. Subduction zone earthquakes, for example, are often discussed to trigger seafloor seepage but causal links that go beyond theoretical considerations have not yet been fully established. This is mainly due to the inaccessibility of offshore epicentral areas, the infrequent occurrence of large earthquakes, and challenges associated with offshore monitoring of seepage over large areas and sufficient time periods. Here we report visual, geochemical, geophysical, and modeling results and observations from the Concepcion Methane Seep Area (offshore Central Chile) located in the rupture area of the 2010 Mw. 8.8 Maule earthquake. High methane concentrations in the oceanic water column and a shallow subbottom depth of sulfate penetration indicate active methane seepage. The stable carbon isotope signature of the methane and hydrocarbon composition of the released gas indicate a mixture of shallow-sourced biogenic gas and a deeper sourced thermogenic component. Pristine fissures and fractures observed at the seafloor together with seismically imaged large faults in the marine fore arc may represent effective pathways for methane migration. Upper plate fault activity with hydraulic fracturing and dilation is in line with increased normal Coulomb stress during large plate-boundary earthquakes, as exemplarily modeled for the 2010 earthquake. On a global perspective our results point out the possible role of recurring large subduction zone earthquakes in driving hydrocarbon seepage from marine fore arcs over long timescales.

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Flux and dispersion of gases from the “Drachenschlund” hydrothermal vent at 8°18' S, 13°30' W on the Mid-Atlantic Ridge

Cited by 85 publications

References 43 publications

Isotope fractionation and mixing in methane plumes from the Logatchev hydrothermal field

Isotope fractionation and mixing in methane plumes from the Logatchev hydrothermal field

Comparative studies of pelagic microbial methane oxidation within the redox zones of the Gotland Deep and Landsort Deep (central Baltic Sea)

Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule earthquake, Central Chile

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