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  • 2010-2014  (7)
  • 2005-2009  (6)
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  • 1
    Online Resource
    Online Resource
    Methane sources, distributions, and fluxes from cold vent sites at Hydrate Ridge, Cascadia Margin (2005)
    Associated volumes
    Details Availability
    In: Global biogeochemical cycles, Hoboken, NJ : Wiley, 1987, 19(2005), 1944-9224
    In: volume:19
    In: year:2005
    In: extent:21
    Type of Medium: Online Resource
    Pages: 21 , graph. Darst
    ISSN: 1944-9224
    DOI: 10.1029/2004GB002266
    Language: English
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  • 2
    Online Resource
    Online Resource
    Methane sources feeding cold seeps on the shelf and upper continental slope off central Oregon, USA (2009)
    Associated volumes
    Details Availability
    In: Geochemistry, geophysics, geosystems, Hoboken, NJ : Wiley, 2000, 10(2009), 11, 1525-2027
    In: volume:10
    In: year:2009
    In: number:11
    In: extent:21
    Description / Table of Contents: We report on a bathymetric mapping and remotely operated vehicle surveys along the 100600 m region offshore Oregon from 43ʿ50?N to 44°18'N. We interpret our results in light of available geophysical data, published geotectonic models, and analogous observations of fluid venting and carbonate deposition from 44°30'N to 45°00'N. The methane seepage is defined by juxtaposition of a young prism, where methane is generated by bacterial activity and its release is modulated by gas hydrate dynamics, against older sequences that serve as a source of thermogenic hydrocarbons that vent in the shelf. We hypothesize that collision of a buried ridge with the Siletz Terrane results in uplift of gas hydrate bearing sediments in the oncoming plate and that the resulting decrease in pressure leads to gas hydrate dissociation and methane exolution, which, in turn, may facilitate slope failure. Oxidation of the released methane results in precipitation of carbonates that are imaged as high backscatter along a 550 ± 60 m benthic corridor.
    Type of Medium: Online Resource
    Pages: 21 , Ill., graph. Darst
    ISSN: 1525-2027
    URL: http://www.agu.org/journals/gc/gc0911/2009GC002518/
    DOI: 10.1029/2009GC002518
    Language: English
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  • 3
    Online Resource
    Online Resource
    In situ hydrocarbon concentrations from pressurized cores in surface sediments, northern Gulf of Mexico (2007)
    Associated volumes
    Details Availability
    In: Marine chemistry, Amsterdam [u.a.] : Elsevier Science, 1972, 107(2007), 4, Seite 498-515, 0304-4203
    In: volume:107
    In: year:2007
    In: number:4
    In: pages:498-515
    Description / Table of Contents: Two newly developed coring devices, the Multi-Autoclave-Corer and the Dynamic Autoclave Piston Corer were deployed in shallow gas hydrate-bearing sediments in the northern Gulf of Mexico during research cruise SO174 (Oct- Nov 2003). For the first time, they enable the retrieval of near-surface sediment cores under ambient pressure. This enables the determination of in situ methane concentrations and amounts of gas hydrate in sediment depths where bottom water temperature and pressure changes most strongly influence gas/hydrate relationships. At seep sites of GC185 (Bush Hill) and the newly discovered sites at GC415, we determined the volume of low-weight hydrocarbons (C1 through C5) from nine pressurized cores via controlled degassing. The resulting in situ methane concentrations vary by two orders of magnitudes between 0.031 and 0.985 mol kg -1 pore water below the zone of sulfate depletion. This includes dissolved, free, and hydrate-bound CH4. Combined with results from conventional cores, this establishes a variability of methane concentrations in close proximity to seep sites of five orders of magnitude. In total four out of nine pressure cores had CH4 concentrations above equilibrium with gas hydrates. Two of them contain gas hydrate volumes of 15% (GC185) and 18% (GC415) of pore space. The measurements prove that the highest methane concentrations are not necessarily related to the highest advection rates. Brine advection inhibits gas hydrate stability a few centimeters below the sediment surface at the depth of anaerobic oxidation of methane and thus inhibits the storage of enhanced methane volumes. Here, computerized tomography (CT) of the pressure cores detected small amounts of free gas. This finding has major implications for methane distribution, possible consumption, and escape into the bottom water in fluid flow systems related to halokinesis.
    Type of Medium: Online Resource
    Pages: Ill., graph. Darst
    ISSN: 0304-4203
    DOI: 10.1016/j.marchem.2007.08.008
    Language: English
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  • 4
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    (Table 1) Analysis of pore water (PW) and hydrocarbon gases (HC) on sediment samples after degassing, and the recovery pressure (pressure) on SO174 samples (2007)
    PANGAEA
    Details
    Publication Date: 2023-07-10
    Keywords: 152; 153; 158; 166; 170; Analysis; Bush Hill; Center for Marine Environmental Sciences; DAPC; Device type; Dynamic autoclave piston corer; Elevation of event; Event label; Latitude of event; Location type; Longitude of event; MAC; MARUM; Multi autoclave corer; OTEGA II; Pressure, water; Sample, optional label/labor no; SO174/1; SO174/1_118; SO174/1_63; SO174/1_90; SO174/1_97; SO174/2; SO174/2_152; SO174/2_153; SO174/2_158; SO174/2_166; SO174/2_170; Sonne
    Type: Dataset
    Format: text/tab-separated-values, 42 data points
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  • 5
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    Gas hydrate structures and C1-C5 hydrocarbons at individual sites in the Gulf of Mexico (2010)
    PANGAEA
    In:  Supplement to: Klapp, Stephan A; Bohrmann, Gerhard; Kuhs, Werner F; Murshed, Mangir M; Pape, Thomas; Klein, Helmut; Techmer, Kirsten S; Heeschen, Katja U; Abegg, Friedrich (2010): Microstructures of structure I and II gas hydrates from the Gulf of Mexico. Marine and Petroleum Geology, 27(1), 116-125, https://doi.org/10.1016/j.marpetgeo.2009.03.004
    Details
    Publication Date: 2024-05-18
    Description: Gas hydrate samples from various locations in the Gulf of Mexico (GOM) differ considerably in their microstructure. Distinct microstructure characteristics coincide with discrete crystallographic structures, gas compositions and calculated thermodynamic stabilities. The crystallographic structures were established by X-ray diffraction, using both conventional X-ray sources and high-energy synchrotron radiation. The microstructures were examined by cryo-stage Field-Emission Scanning Electron Microscopy (FE-SEM). Good sample preservation was warranted by the low ice fractions shown from quantitative phase analyses. Gas hydrate structure II samples from the Green Canyon in the northern GOM had methane concentrations of 70-80% and up to 30% of C2-C5 of measured hydrocarbons. Hydrocarbons in the crystallographic structure I hydrate from the Chapopote asphalt volcano in the southern GOM was comprised of more than 98% methane. Fairly different microstructures were identified for those different hydrates: Pores measuring 200-400 nm in diameter were present in structure I gas hydrate samples; no such pores but dense crystal surfaces instead were discovered in structure II gas hydrate. The stability of the hydrate samples is discussed regarding gas composition, crystallographic structure and microstructure. Electron microscopic observations showed evidence of gas hydrate and liquid oil co-occurrence on a micrometer scale. That demonstrates that oil has direct contact to gas hydrates when it diffuses through a hydrate matrix.
    Keywords: 140; 157-1; 169; Bush Hill; Campeche Knoll; Center for Marine Environmental Sciences; Chapopote; GC; GeoB10618; Gravity corer; M67/2b; MARUM; Meteor (1986); OTEGA II; SO174/1; SO174/1_47-1; SO174/1_96; SO174/2; SO174/2_140; SO174/2_157-1; SO174/2_169; Sonne; Television-Grab; TVG
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 6
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    (Table 3) C1-C5 hydrocarbons measured from purposefully decomposed gas hydrate samples from the Gulf of Mexico (2010)
    PANGAEA
    Details
    Publication Date: 2024-05-18
    Keywords: 140; 157-1; 169; Area/locality; Bush Hill; C1 hydrocarbons; C2 hydrocarbons; C3 hydrocarbons; C5-isomers hydrocarbons; Campeche Knoll; Center for Marine Environmental Sciences; Chapopote; Comment; Elevation of event; Event label; Gas chromatography - Flame Ionization Detection (GC-FID); GC; GeoB10618; Gravity corer; iso-C4 hydrocarbons; Latitude of event; Longitude of event; M67/2b; MARUM; Meteor (1986); n-C4 hydrocarbons; Number; OTEGA II; Sample code/label; SO174/1; SO174/1_47-1; SO174/1_96; SO174/2; SO174/2_140; SO174/2_157-1; SO174/2_169; Sonne; Television-Grab; TVG
    Type: Dataset
    Format: text/tab-separated-values, 123 data points
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    DATA PANGAEA
  • 7
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    (Table 2) Gas hydrate structures at individual sites in the Gulf of Mexico (2010)
    PANGAEA
    Details
    Publication Date: 2024-05-18
    Keywords: 140; 157-1; 169; Area/locality; Bush Hill; Campeche Knoll; Center for Marine Environmental Sciences; Chapopote; Comment; Elevation of event; Event label; GC; GeoB10618; Gravity corer; Hydrate; Latitude of event; Longitude of event; M67/2b; MARUM; Meteor (1986); OTEGA II; Sample code/label; SO174/1; SO174/1_47-1; SO174/1_96; SO174/2; SO174/2_140; SO174/2_157-1; SO174/2_169; Sonne; Television-Grab; TVG; X-ray diffraction (XRD)
    Type: Dataset
    Format: text/tab-separated-values, 93 data points
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    DATA PANGAEA
  • 8
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    Authigenic carbonates from the Darwin Mud Volcano, Gulf of Cadiz : a record of palaeo-seepage of hydrocarbon bearing fluids (2012)
    Elsevier
    In:  Chemical Geology, 300-301 . pp. 24-39.
    Details
    Publication Date: 2017-12-07
    Description: Hydrocarbon-rich fluids expelled at mud volcanoes (MVs) may contribute significantly to the carbon budget of the oceans, but little is known about the long-term variation in fluid fluxes at MVs. The Darwin MV is one of more than 40 MVs located in the Gulf of Cadiz, but it is unique in that its summit is covered by a thick carbonate crust that has the potential to provide a temporal record of seepage activity. In order to test this idea, we have conducted petrographic, chemical and isotopic analyses of the carbonate crust. In addition a 1-D transport-reaction model was applied to pore fluid data to assess fluid flow and carbonate precipitation at present. The carbonate crusts mainly comprise of aragonite, with a chaotic fabric exhibiting different generations of cementation and brecciation. The crusts consist of bioclasts and lithoclasts (peloids, intraclasts and extraclasts) immersed in a micrite matrix and in a variety of cement types (microsparite, botryoidal, isopachous acicular, radial and splayed fibrous). The carbonates are moderately depleted in 13C (δ13C = − 8.1 to − 27.9‰) as are the pore fluids (δ13C = − 19.1 to − 28.7‰), which suggests that their carbon originated from the oxidation of methane and higher hydrocarbons, like the gases that seep from the MV today. The carbonate δ18O values are as high as 5.1‰, and it is most likely that the crusts formed from 18O-rich fluids derived from dehydration of clay minerals at depth. Pore fluid modelling results indicate that the Darwin MV is currently in a nearly dormant phase (seepage velocities are 〈 0.09 cm yr− 1). Thus, the thick carbonate crust must have formed during past episodes of high fluid flow, alternating with phases of mud extrusion and uplift. Highlights ► Results of pore fluid modelling indicate low seepage activity at localised sites. ► Pore fluids are supersaturated with respect to hydrocarbons of thermogenic origin. ► AOM supports vent fauna and results in the formation of authigenic carbonates. ► The carbonate crust has a brecciated appearance and mainly consists of aragonite. ► The crust formation seems to be regulated by changes in fluid and mudflow activity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.chemgeo.2012.01.006
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Spatial variation in fluid flow and geochemical fluxes across the sediment–seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz) (2011)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 75 (4). pp. 1124-1144.
    Details
    Publication Date: 2017-09-27
    Description: Submarine mud volcanism is an important pathway for transfer of deep-sourced fluids enriched in hydrocarbons and other elements into the ocean. Numerous mud volcanoes (MVs) have been discovered along oceanic plate margins, and integrated elemental fluxes are potentially significant for oceanic chemical budgets. Here, we present the first detailed study of the spatial variation in fluid and chemical fluxes at the Carlos Ribeiro MV in the Gulf of Cadiz. To this end, we combine analyses of the chemical composition of pore fluids with a 1-D transport-reaction model to quantify fluid fluxes, and fluxes of boron, lithium and methane, across the sediment–seawater interface. The pore fluids are significantly depleted in chloride, but enriched in lithium, boron and hydrocarbons, relative to seawater. Pore water profiles of sulphate, hydrogen sulphide and total alkalinity indicate that anaerobic oxidation of methane occurs at 34–180 cm depth below seafloor. Clay mineral dehydration, and in particular the transformation of smectite to illite, produces pore fluids that are depleted in chloride and potassium. Profiles of boron, lithium and potassium are closely related, which suggests that lithium and boron are released from the sediments during this transformation. Pore fluids are expelled into the water column by advection; fluid flow velocities are 4 cm yr−1 at the apex of the MV but they rapidly decrease to 0.4 cm yr−1 at the periphery. The associated fluxes of boron, lithium and methane vary between 7–301, 0.5–6 and 0–806 mmol m−2 yr−1, respectively. We demonstrate that fluxes of Li and B due to mud volcanism may be important on a global scale, however, release of methane into the overlying water column is suppressed by microbial methanotrophy.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.gca.2010.11.017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Microstructures of structure I and II gas hydrates from the Gulf of Mexico (2010)
    Elsevier
    In:  Marine and Petroleum Geology, 27 (1). pp. 116-125.
    Details
    Publication Date: 2017-07-31
    Description: Gas hydrate samples from various locations in the Gulf of Mexico (GOM) differ considerably in their microstructure. Distinct microstructure characteristics coincide with discrete crystallographic structures, gas compositions and calculated thermodynamic stabilities. The crystallographic structures were established by X-ray diffraction, using both conventional X-ray sources and high-energy synchrotron radiation. The microstructures were examined by cryo-stage Field-Emission Scanning Electron Microscopy (FE-SEM). Good sample preservation was warranted by the low ice fractions shown from quantitative phase analyses. Gas hydrate structure II samples from the Green Canyon in the northern GOM had methane concentrations of 70–80% and up to 30% of C2–C5 of measured hydrocarbons. Hydrocarbons in the crystallographic structure I hydrate from the Chapopote asphalt volcano in the southern GOM was comprised of more than 98% methane. Fairly different microstructures were identified for those different hydrates: Pores measuring 200–400 nm in diameter were present in structure I gas hydrate samples; no such pores but dense crystal surfaces instead were discovered in structure II gas hydrate. The stability of the hydrate samples is discussed regarding gas composition, crystallographic structure and microstructure. Electron microscopic observations showed evidence of gas hydrate and liquid oil co-occurrence on a micrometer scale. That demonstrates that oil has direct contact to gas hydrates when it diffuses through a hydrate matrix.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.marpetgeo.2009.03.004
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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