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Han, Xiqiu; Suess, Erwin; Huang, Yong-Jiang; Wu, Nengyou; Bohrmann, Gerhard; Su, Xin; Eisenhauer, Anton; Rehder, Gregor; Fang, Yinxia (2008): (Table 2) Mineralogy, stable isotopes, and mineral percentages of the carbonate fraction of samples from the South China Sea. PANGAEA, https://doi.org/10.1594/PANGAEA.771248, Supplement to: Han, X et al. (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

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Abstract:
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.
Coverage:
Median Latitude: 22.097297 * Median Longitude: 118.794340 * South-bound Latitude: 22.047083 * West-bound Longitude: 118.723083 * North-bound Latitude: 22.151000 * East-bound Longitude: 118.872767
Date/Time Start: 2004-06-11T05:00:00 * Date/Time End: 2004-06-27T11:12:00
Minimum Elevation: -771.0 m * Maximum Elevation: -473.0 m
Event(s):
SO177/1-28 (TVG-1) * Latitude: 22.151000 * Longitude: 118.872400 * Date/Time: 2004-06-11T05:00:00 * Elevation: -498.0 m * Campaign: SO177/1 (SIGER) * Basis: Sonne * Method/Device: Television-Grab (TVG) * Comment: carbonate, chemoherm like struct.
SO177/1-29 (TVG-2) * Latitude: 22.149000 * Longitude: 118.872767 * Date/Time: 2004-06-11T06:43:00 * Elevation: -484.0 m * Campaign: SO177/1 (SIGER) * Basis: Sonne * Method/Device: Television-Grab (TVG) * Comment: carbonate, chemoherm like struct.
SO177/1-30 (TVG-3) * Latitude: 22.149717 * Longitude: 118.872283 * Date/Time: 2004-06-11T08:51:00 * Elevation: -473.0 m * Campaign: SO177/1 (SIGER) * Basis: Sonne * Method/Device: Television-Grab (TVG) * Comment: carbonate, chemoherm like struct.
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1Event labelEvent
2Latitude of eventLatitude
3Longitude of eventLongitude
4Elevation of eventElevationm
5Sample code/labelSample labelHan, XiqiuSample code
6DescriptionDescriptionHan, XiqiuDescription and sampling position
7δ13C, carbonateδ13C carb‰ PDBHan, XiqiuMass spectrometer Finnigan MAT 252
8δ18O, carbonateδ18O carb‰ PDBHan, XiqiuMass spectrometer Finnigan MAT 252
9Low magnesium calciteLMC%Han, XiqiuCalculated, see reference(s)Relative weight percentage
10High magnesium calciteHMC%Han, XiqiuCalculated, see reference(s)Relative weight percentage / with MgCO3 / (mol %) /5-10
11High magnesium calciteHMC%Han, XiqiuCalculated, see reference(s)Relative weight percentage / with MgCO3 / (mol %) / 10-15
12High magnesium calciteHMC%Han, XiqiuCalculated, see reference(s)Relative weight percentage / with MgCO3 / (mol %) / 15-20
13High magnesium calciteHMC%Han, XiqiuCalculated, see reference(s)Relative weight percentage / with MgCO3 / (mol %) / 30-40
14DolomiteDol%Han, Xiqiu
15AragoniteArg%Han, Xiqiu
Size:
660 data points

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