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  • 1
    Book
    Book
    Methane and gas hydrate geology of the Northern South China Sea : Sino-German Cooperative SO-177 cruise report ; [SiGer 2004, South China Sea Continental Margin: Geological Methane Budget and Environmental Effects of Methane Emissions and Gashydrates ; cooperative research between IFM-GEOMAR, Kiel, Germany and Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou, Guangdong Province, P.R. China ; Leg 1: Hong Kong - Hong Kong, 02.06.-23.06.2004 ; Leg 2a: Hong Kong - Shanghai, 24.06.-5.07.2004 ; Leg 2b: Shanghai - Pusan, 16.07.-19.07.2004] (2008)
    [Guangzhou] : Geological Publ. House
    Details Availability
    Keywords: Forschungsbericht
    Type of Medium: Book
    Pages: 197 S, , zahlr. Ill., graph. Darst., Kt.
    ISBN: 9787116059184
    Language: Chinese
    Note: Engl.-chines. Ausg. u.d.T.: FS Sonne Fahrtbericht/Cruise report SO177, SiGer 2004 , In chines. Schrift. - Teilnehmerverz., Datenanhänge und Literaturverz. in latein. Schrift
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  • 2
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    (Table 2) Mineralogy, stable isotopes, and mineral percentages of the carbonate fraction of samples from the South China Sea
    PANGAEA
    In:  Supplement to: Han, Xiqiu; Suess, Erwin; Huang, Yong-Jiang; Wu, Nengyou; Bohrmann, Gerhard; Su, Xin; Eisenhauer, Anton; Rehder, Gregor; Fang, Yinxia (2008): Jiulong Methane Reef: Microbial mediation seep-carbonates in the South China Sea. Marine Geology, 249(3-4), 243-256, https://doi.org/10.1016/j.margeo.2007.11.012
    Details
    Publication Date: 2023-05-12
    Description: Chemoherm carbonates, as well as numerous other types of methane seep carbonates, were discovered in 2004 along the passive margin of the northern South China Sea. Lithologically, the carbonates are micritic containing peloids, clasts and clam fragments. Some are highly brecciated with aragonite layers of varying thicknesses lining fractures and voids. Dissolution and replacement is common. Mineralogically, the carbonates are dominated by high magnesium calcites (HMC) and aragonite. Some HMCs with MgCO3 contents of between 30–38 mol%–extreme-HMC, occur in association with minor amounts of dolomite. All of the carbonates are strongly depleted in d13C, with a range from -35.7 to -57.5 per mil PDB and enriched in d18O (+ 4.0 to + 5.3 per mil PDB). Abundant microbial rods and filaments were recognized within the carbonate matrix as well as aragonite cements, likely fossils of chemosynthetic microbes involved in carbonate formation. The microbial structures are intimately associated with mineral grains. Some carbonate mineral grains resemble microbes. The isotope characteristics, the fabrics, the microbial structure, and the mineralogies are diagnostic of carbonates derived from anaerobic oxidation of methane mediated by microbes. From the succession of HMCs, extreme-HMC, and dolomite in layered tubular carbonates, combined with the presence of microbial structure and diagenetic fabric, we suggest that extreme-HMC may eventually transform into dolomites. Our results add to the worldwide record of seep carbonates and establish for the first time the exact locations and seafloor morphology where such carbonates formed in the South China Sea. Characteristics of the complex fabric demonstrate how seep carbonates may be used as archives recording multiple fluid regimes, dissolution, and early transformation events.
    Keywords: Aragonite; Calculated, see reference(s); Description; Dolomite; Elevation of event; Event label; High magnesium calcite; IFM-GEOMAR; Latitude of event; Leibniz-Institut für Meereswissenschaften, Kiel; Longitude of event; Low magnesium calcite; Mass spectrometer Finnigan MAT 252; Sample code/label; SIGER; SO177/1; SO177/1-28; SO177/1-29; SO177/1-30; SO177/1-50; SO177/1-51; SO177/1-52; SO177/1-53; SO177/1-72; SO177/2; SO177/2-91; SO177/2-92; Sonne; Television-Grab; TVG; TVG-1; TVG-11; TVG-13; TVG-14; TVG-2; TVG-3; TVG-6; TVG-7; TVG-8; TVG-9; δ13C, carbonate; δ18O, carbonate
    Type: Dataset
    Format: text/tab-separated-values, 660 data points
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    DATA PANGAEA
  • 3
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    Molecular Mechanisms of Gas Diffusion in CO2Hydrates (2016)
    ACS
    In:  The Journal of Physical Chemistry C, 120 (30). pp. 16298-16304.
    Details
    Publication Date: 2019-02-01
    Description: Gas diffusion is considered a rate-limiting step in the formation of gas hydrates, yet its molecular mechanisms remain unclear. In this work, we present the molecular mechanisms of the CO2 cage-to-cage transport in gas hydrates, as directly observed from molecular dynamics simulations performed at elevated temperatures. We found that at least one water vacancy is required for the CO2 molecules to pass through five-membered water rings, while only the distortion of the local ring structure is required for the CO2 molecules to pass through the six-membered water rings. We used the transition-state theory to estimate the relevant kinetic parameters associated with the CO2 diffusion in gas hydrates. The calculated free energy of activation is about 44 ± 6 kJ/mol, and the diffusion coefficient is in the range of 1.0 × 10–16∼2.0 × 10–14 m2/s, for the CO2 diffusion at 270 K, in close agreement with previous experiments. This work suggests that the presence of empty cages is crucial for the CO2 cage-to-cage transport in gas hydrates.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1021/acs.jpcc.6b03111
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Methane seepage inferred from pore water geochemistry in shallow sediments in the western slope of the Mid-Okinawa Trough (2018)
    Elsevier
    In:  Marine and Petroleum Geology, 98 . pp. 306-315.
    Details
    Publication Date: 2021-02-08
    Description: Widely distributed cold seeps are crucial sources of carbon to the seawater, whereas anaerobic oxidation of methane (AOM) and precipitation of authigenic carbonate might change the compositions of the methane-rich fluids and thus reduce the outputs of dissolved carbon to seawater. In this work, we analyze the pore water compositions of four gravity cores with high methane concentration abnormalities in pore water or in overlying seawater in the western slope of the Mid-Okinawa Trough. For the northern research area, active weak methane seepage through the seafloor is identified in the vicinity of mud volcanoes (sites C01 and C10), and strong emissions of gas and fluids may occur in the central mud volcanoes. In a submarine canyon at the south, C23 site exhibits rarely methane seepage, while high rate transportation of methane from deep sediments and associated AOM are identified at site C25 where small vertical faults and gas-bearing layers are developed at the surrounding. AOM at site C25 is indicated by (1) quasi-linearly decrease of sulfate concentrations with depths, (2) intense increases of dissolved inorganic carbon (DIC) concentrations and (3) significantly negative δ13C values (vary from −7.2 to −26.3‰) of DIC. Organoclastic degradation in the shallow sediments is not obviously recognized in the study area because of the low concentrations of NH4+, as well as negligible sulfate consumption at three of the four sites. Our data reveal that the cold systems are one of the DIC sources (the fluxes are ca. 11.2 mmol/m2/yr) to the seawater in the Okinawa Trough, which can be tracked by high depletion of 13C (δ13CDIC ranges from −7.2 to −26.3‰ VPDB).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.marpetgeo.2018.08.021
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Hydrothermal metal supplies enhance the benthic methane filter in oceans: An example from the Okinawa Trough (2019)
    Elsevier
    In:  Chemical Geology, 525 . pp. 190-209.
    Details
    Publication Date: 2022-01-31
    Description: Highlights • Three distinct types of carbonates exist in cold seeps in the Okinawa Trough. • Carbonate forms between lower part of SMTZ and upper part of methanogenic zone. • Hydrothermal has the potential to foster Fe-AOM in cold seep sediment. • Metal-AOM might have an influence on early Earth's methane flux and metal cycle. Abstract Anaerobic oxidation of methane (AOM) is an important process that regulates methane budget in the global carbon cycle. Sulfate is traditionally regarded as the most important electron acceptor for AOM. However, recent studies reveal that reactive metal reduction-driven AOM (metal-AOM) may also present on natural environments. Partitioning the methane-C sink from anaerobic oxidation between sulfate reduction-driven AOM (sulfate-AOM) and metal-AOM is thus becoming a scientific challenge to be addressed. This study aimed to show that metal-AOM has a potential to complement sulfate-AOM, especially when methane seeps met sediments enriched in iron and manganese oxides supplied by hydrothermal plumes. Samples of authigenic carbonate were collected from the cold seeps on the western slope of the Okinawa Trough (OT), a semi-enclosed back-arc basin with cold seeps and hydrothermal activities coexist spatially. Petrologic and mineralogical observations provided faithful evidence of a close genetic relationship between goethite and authigenic carbonates, likely indicating the presence of metal-AOM although some contributions of organoclastic Fe reduction cannot be ruled out. The most possible place of metal-AOM was between the lower part of the sulfate–methane transition zone (SMTZ) and the immediate upper part of the methanogenic zone. The characteristics of δ13Ccarb [−53.7‰ to −3.3‰ Vienna-PeeDee Belemnite (VPDB)] also point to our carbonate samples as the products of AOM. These authigenic carbonates was further identified as three possible types of carbonate of different sources: sulfate-AOM, metal-AOM, and hydrothermal carbonates, depending on the correlations among concentrations of carbonate-associated sulfate (CAS), δ13Ccarb, and δ18Ocarb. Based on these findings, we tentatively suggested that the reduction of reactive metals carried by hydrothermal plumes might drive the methane oxidation in the adjacent cold seep areas, resulting in the precipitation of unique carbonates and enhancement the efficiency of “the benthic methane filter”. This study reported the coupling or interaction between the two extreme submarine environments by metal-AOM for the first time, which might help in understanding and improving the global carbon and metal cycles now and in the past. Previous article in issue
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.chemgeo.2019.07.025
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Changes in reaction surface during the methane hydrate dissociation and its implications for hydrate production (2021)
    Elsevier
    In:  Energy, 230 . Art.Nr. 120848.
    Details
    Publication Date: 2022-01-07
    Description: The reaction surface area of hydrate (RSAH) inherently controls the reaction rate of hydrate dissociation in the pore spaces, which further affects the gas production behaviour of the hydrate-bearing sediments. The objective of this work is to measure and describe the RSAH evolution during MH dissociation and analyse its implications for gas production. The CT images obtained from different dissociation stages showed the RSAH decreased slowly in the early stage of dissociation and rapidly in the later stage. By considering the pore structure features of sediment, a fractal method was proposed to predict the relationship between RSAH and hydrate saturation, which showed better agreement with the CT experimental results than that of Yousif's model. Further hydrate production numerical simulations embedded with different RSAH predictions indicated that the hydrate production process was significantly influenced by the variations in RSAH. The simulated gas production rate based on the fractal model was lower than that of Yousif's model, the far-field pressure drop in the fractal model was slower, and the advance of the dissociation front and the transfer of the pressure field in Yousif's model was faster than that of the fractal model. Highlights • The changes in hydrate reaction surface area during hydrate dissociation are experimentally measured and analysed. • A fractal model considering the pore structure characteristics of porous media is proposed and experimentally validated. • A comparison of the hydrate dissociation rate predicted by the proposed fractal model and by Yousif’s model is made. • Implications of reaction surface evolution during the hydrate dissociation for hydrate productions are modeled.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.energy.2021.120848
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Coupled thermal-hydrodynamic-mechanical–chemical numerical simulation for gas production from hydrate-bearing sediments based on hybrid finite volume and finite element method (2022)
    Elsevier
    Details
    Publication Date: 2024-01-08
    Description: Gas production from hydrates induced by depressurization is a complex thermal-hydrodynamic-mechanical–chemical (THMC) coupled process. In this paper, we present a THMC coupled model to simulate the fluid flow in hydrate-bearing sediments (HBS) and the geomechanical behavior of HBS. The model is made of two subsystems, which are the fluid part of non-isothermal multi-phase flow with hydrate kinetic and solid part of geomechanical deformation. It accounts for two-way coupling effects between these two subsystems, i.e. the effect of pore pressure and hydrate dissociation on the solid mechanical behavior and the effect of stress on the hydraulic behavior. A new numerical method based on the hybrid control volume finite element method (CVFEM)-finite element method (FEM) is developed to solve the mathematical models. The local conservative CVFEM is used for the fluid part, and the standard FEM for the solid part. In the framework of hybrid CVFEM-FEM, the local conservation is reserved and the primary variables for the two subsystem are co-located. A multi-point flux approximation (MPFA) is adopted without orthogonal meshes so that it is very flexible to build complex geometrical models. The accuracy and reliability of the newly developed simulator QIMGHyd-THMC are tested by comparing with two experimental examples and a large-scale benchmark problem of other popular simulators.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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