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Feng, Dong; Chen, Duofu; Peckmann, Jörn; Bohrmann, Gerhard (2010): Mineral composition, rare earth elements, and trace elements from samples of the northern Congo deep-sea fan. PANGAEA, https://doi.org/10.1594/PANGAEA.771775, Supplement to: Feng, D et al. (2010): Authigenic carbonates from methane seeps of the northern Congo fan: Microbial formation mechanism. Marine and Petroleum Geology, 27, 748-756, https://doi.org/10.1016/j.marpetgeo.2009.08.006

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Abstract:
Authigenic carbonates were collected from methane seeps at Hydrate Hole at 3113 m water depth and Diapir Field at 2417 m water depth on the northern Congo deep-sea fan during RV Meteor cruise M56. The carbonate samples analyzed here are nodules, mainly composed of aragonite and high-Mg calcite. Abundant putative microbial carbonate rods and associated pyrite framboids were recognized within the carbonate matrix. The d13C values of the Hydrate Hole carbonates range from -62.5 permil to -46.3 permil PDB, while the d13C values of the Diapir Field carbonate are somewhat higher, ranging from -40.7 permil to -30.7 permil PDB, indicating that methane is the predominant carbon source at both locations. Relative enrichment of 18O (d18O values as high as 5.2 permil PDB) are probably related to localized destabilization of gas hydrate. The total content of rare earth elements (REE) of 5% HNO3-treated solutions derived from carbonate samples varies from 1.6 ppm to 42.5 ppm. The shale-normalized REE patterns all display positive Ce anomalies (Ce/Ce* > 1.3), revealing that the carbonates precipitated under anoxic conditions. A sample from Hydrate Hole shows a concentric lamination, corresponding to fluctuations in d13C values as well as trace elements contents. These fluctuations are presumed to reflect changes of seepage flux.
Coverage:
Median Latitude: -5.496667 * Median Longitude: 10.166917 * South-bound Latitude: -6.184000 * West-bound Longitude: 9.908333 * North-bound Latitude: -4.809333 * East-bound Longitude: 10.425500
Date/Time Start: 2002-12-17T18:02:00 * Date/Time End: 2002-12-21T13:26:00
Event(s):
GeoB8212-2 * Latitude: -4.809333 * Longitude: 9.908333 * Date/Time: 2002-12-17T18:02:00 * Elevation: -3113.0 m * Recovery: 0.5 m * Location: Congo Fan * Campaign: M56/2 * Basis: Meteor (1986) * Method/Device: Television-Grab (TVG) * Comment: Olive mud, carbonates large, Pogonophores, black layers, strong gas release, H2S odour
GeoB8215-2 * Latitude: -6.184000 * Longitude: 10.425500 * Date/Time: 2002-12-21T13:26:00 * Elevation: -2417.0 m * Recovery: 0.5 m * Location: Congo Fan * Campaign: M56/2 * Basis: Meteor (1986) * Method/Device: Television-Grab (TVG) * Comment: Clam field, completely filled with carbonates in olive mud, plenty of dead molluscs, 1 shovel broken, oily films
Size:
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