GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Elsevier  (3)
  • Forschungszentrum Jülich GmbH  (1)
  • 1995-1999  (4)
Document type
Publisher
Years
Year
  • 1
    facet.materialart.
    Unknown
    Geochemistry at a sealed deep-sea borehole of the Cascadia Margin (1998)
    Elsevier
    In:  Marine Geology, 148 . pp. 9-20.
    Details
    Publication Date: 2017-06-27
    Description: The deep-sea borehole seal CORK was deployed for the first time on a modern accretionary prism during ODP Leg 146 to the Cascadia Margin. Ten months after the deployment the fluid flow and geochemistry of the borehole fluids was investigated during several dives by DSRV Alvin. The chemical analysis of the borehole fluids revealed methane concentrations of more than 3.5 mM, whereas oxygen and dissolved ions as Cl, NO3, or PO4 are still close to the ambient seawater composition. The exceedingly high methane content measured at the top of the sealed borehole and the observed degassing during the ascent of the submersible indicates that the sampled fluid was initially saturated or close to saturation with respect to CH4. The hydrocarbons are characterized by ratios of 170–200 and δ13C values of − 59.5 to − 62.4%o which indicates a considerable admixture of thermogenic hydrocarbon gases. The occurrence of methane of partly thermogenic origin demonstrates that CH4 enters the sealed borehole in the lower, perforated section (94–178 mbsf) and accumulates at the top of the borehole. This suggests the occurrence of free gas within the encapsulated borehole. Considering the stability field of CH4-hydrates, the formation of these ice-like structures may take place and potentially results in a clogging of the top of the borehole. Such precipitates could result in a decoupling of the top of the borehole from the hydraulic and geochemical regime of the accretionary complex, an important aspect for future plans of CORK deployments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0025-3227(98)00016-4
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
    facet.materialart.
    Unknown
    Quantifying fluid flow, solute mixing and biogeochemical turnover at cold vents of the eastern Aleutian subduction zone (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 (24). pp. 5209-5219.
    Details
    Publication Date: 2017-08-03
    Description: In situ oxygen fluxes were measured at vent sites in the Aleutian trench at a water depth of almost 5000 m using a TV-guided benthic flux chamber. The flux was 2 orders of magnitude greater than benthic oxygen fluxes in areas unaffected by venting on the continental margin off Alaska. Porewater profiles taken from the surface sediment below a vent site showed high concentrations of sulfide, methane, and ammonia. The reduced carbon and nitrogen compounds are transported to the vent site by fluids expelled from deeper anoxic sediment layers by the forces of plate convergence. The tectonically driven fluid flow was determined from the biochemical turnover in vent communities and was found to be 3.4 ± 0.5 m yr−1. A model was used to quantify the transport of silica, Ca2+, and sulfate via diffusion, advection, and bioirrigation through the surface sediments of a vent site. A nonlocal mixing coefficient of 20–30 yr−1 was determined by fitting the model curves to the measured porewater profiles showing that the transport of solutes within the near-surface sediments and across the sediment-water interface is dominated by the activity of the vent fauna. Sulfate-containing oceanic bottom water and methane-rich vent fluids were mixed below the clam colony to produce sulfide and a CaCO3 precipitate. The vent biota shape their immediate environment and control the sediment-water exchange and the benthic fluxes at vent sites. The oxygen consumption at vent sites is a major sink for oxygen at the study area.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/s0016-7037(97)00306-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
    facet.materialart.
    Unknown
    Gas seeps and methane in the water column at the Makran accretionary wedge (1999)
    Forschungszentrum Jülich GmbH
    In:  [Paper] In: Statusseminar Meeresforschung mit FS Sonne 1999, 10.-12.03.1999, Freiberg, Germany . Meeresforschung mit FS Sonne ; pp. 229-230 .
    Details
    Publication Date: 2020-05-28
    Type: Conference or Workshop Item , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Conference paper
  • 4
    facet.materialart.
    Unknown
    Gas hydrate destabilization: enhanced dewatering, benthic material turnover and large methane plumes at the Cascadia convergent margin (1999)
    Elsevier
    In:  Earth and Planetary Science Letters, 170 . pp. 1-15.
    Details
    Publication Date: 2017-06-29
    Description: Mixed methane–sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the Cascadia convergent margin. Vent fields from which methane-charged, low-salinity fluids containing sulfide, ammonia, 4He, and isotopically light CO2 escape are associated with these exposures. They characterize a newly recognized mechanism of dewatering at convergent margins, where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward. This process augments the convergence-generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate. Discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths. The enhanced turnover results from the oxidation of methane, hydrogen sulfide, and ammonia by vent biota. The injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide. A large fraction of the methane is oxidized within the water column and generates δ13C anomalies of the dissolved inorganic carbon pool.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0012-821X(99)00092-8
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...