Magnetic Susceptibility in Surface Sediments in the Southern South China Sea and Its Implication for Sub-sea Methane Venting

In order to understand the characteristics of magnetic variability and their possible implication for sub,sea methane venting, magnetic susceptibility （MS） of 145 surface sediment samples from the southern South China Sea （SCS） was investigated. Magnetic particles extracted from 20 representative sa...

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Bibliographic Details
Published in:Journal of earth science (Wuhan, China) China), 2009-02, Vol.20 (1), p.193-204
Main Author: 陈忠 颜文 汤贤赞 刘建国 陈木宏 杨华平
Format: Article
Language:English
Subjects:
Biogeosciences
Chemical analysis
Continental shelves
Earth and Environmental Science
Earth science
Earth Sciences
Geochemistry
Geology
Geotechnical Engineering & Applied Earth Sciences
Magnetism
Manganese
Marine
Marine geology
Methane
Ocean floor
Oceans
Pyrite
Seawater
Sediment samplers
Sediments
Sulfides
Water analysis
中南部
南海南部
甲烷排放
硫化物矿物
磁化率
磁黄铁矿
表层沉积物
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Summary:In order to understand the characteristics of magnetic variability and their possible implication for sub,sea methane venting, magnetic susceptibility （MS） of 145 surface sediment samples from the southern South China Sea （SCS） was investigated. Magnetic particles extracted from 20 representative samples were also examined for their mineral, chemical compositions and micromorphology. Results indicate that MS values range between -7.73×10^-8 and 45.06×10^-8m^3/kg. The high MS zones occur at some hydrocarbon-bearing basins and along main tectonic zones, and low ones are distributed mainly within the river delta or along continental shelves. Iron concretions and manganese concretions are not main contributors for high MS values in sediments, while authigenic iron sulphide minerals are possibly responsible for the MS enhancement. This phenomenon is suspected to be produced by the reducing environment where the high upward venting methane beneath the seafloor reacts with seawater sulfate, resulting in seep precipitation of highly susceptible intermediate mineral pyrrhotite, greigite and paramagnetic pyrite. It suggests that MS variability is possibly one of the geochemical indicators for mapping sub-sea zones of methane venting in the southern SCS.
ISSN:1674-487X
1867-111X
DOI:10.1007/s12583-009-0019-y