Authigenic carbonates from methane seeps of the northern Congo Fan; microbial formation mechanism

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doi: 10.1016/j.marpetgeo.2009.08.006
Author(s): Feng Dong; Chen Duofu; Peckmann, Jörn; Bohrmann, Gerhard
Author Affiliation(s): Primary:
Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, Guangzhou, China
Other:
Universität Bremen, Germany
Volume Title: Marine and Petroleum Geology
Source: Marine and Petroleum Geology, 27(4), p.748-756. Publisher: Elsevier, Oxford, United Kingdom. ISSN: 0264-8172
Note: In English. 63 refs.; illus., incl. 2 tables, sketch map
Summary: 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 δ13C values of the Hydrate Hole carbonates range from -62.5 ppm to -46.3 ppm PDB, while the δ13C values of the Diapir Field carbonate are somewhat higher, ranging from -40.7 ppm to -30.7 ppm PDB, indicating that methane is the predominant carbon source at both locations. Relative enrichment of 18O (δ18O values as high as 5.2 ppm 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 δ13C values as well as trace elements contents. These fluctuations are presumed to reflect changes of seepage flux. Abstract Copyright (2010) Elsevier, B.V.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 29 Economic Geology, Energy Sources; Africa; Aliphatic hydrocarbons; Alkanes; Angola Basin; Atlantic Ocean; Authigenic minerals; Basin analysis; Basins; Biochemistry; Biogenic processes; C-13/C-12; Carbon; Carbonate sediments; Carbonates; Chemical composition; Congo Basin; Congo Fan; Crystal chemistry; Diapir Field; Gas hydrates; Geochemistry; Hydrocarbons; Isotope ratios; Isotopes; Leg 175; Lower Congo Basin; Marine sediments; Metals; Methane; Microorganisms; Mineral composition; O-18/O-16; ODP Site 1077; Ocean Drilling Program; Offshore; Oil and gas fields; Oil seeps; Organic compounds; Oxygen; Petroleum; Petroleum exploration; Rare earths; SEM data; Sedimentary basins; Sedimentary petrology; Sediments; South Atlantic; Southeast Atlantic; Stable isotopes; Submarine fans; Textures; Trace elements; X-ray diffraction data
Coordinates: S051048 S051048 E0102611 E0102611
S063000 S040000 E0110000 E0100000
Record ID: 2011027162
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands