期刊
JOURNAL OF ASIAN EARTH SCIENCES
卷 92, 期 -, 页码 293-301出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jseaes.2014.05.004
关键词
Pyrite; Marcasite; Spherule; Framboid; Anaerobic oxidation of methane; AOM; South China Sea
资金
- Natural Science Foundation of China [41306061, 41273022, 91128101]
- Natural Science Foundation of Guangdong Province, China [S2012040007118]
- NASA Astrobiology Institute [N07-5489]
- Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme
- National 127 project
In order to understand the response of authigenic pyrite to gas hydrate geo-systems, pyrite tubes or rods at the sulfate methane transition (SMT) zone of cord GC10 from the northern continental slope of the South China Sea (SCS) were investigated. In situ X-ray diffraction (XRD) results show that the pyrite tube consists of pyrite micro-crystals with trace amount of graphite in the inner tube. Scanning electron microscope (SEM) observations of pyrite tubes indicate various aggregations in the form of framboidal, euhedral, and colloidal pyrite microcrystals. Typical framboidal pyrite is considered as packing of octahedral microcrystals. Interestingly, many framboids in the tubes consist of round or irregular microcrystals and have an outer crust that consists of secondary pyrite. The size of the framboids in the inner wall of the tube is larger than that in the middle wall or foraminifer-filled pyrite. High-resolution transmission electron microscopic (HRTEM) images show marcasite lamellae defects in the spherulitic pyrite crystals, which reveal different solution conditions during the pyrite precipitation. Nano-foil-like graphitic carbon was observed to be closely associated with the pyrite spherules. The occurrence of both marcasite layers and nano-foil-like graphitic carbon suggest that the migration of methane from deep sediment. It is suggested that the formation of pyrite serves as a catalyst during the reaction from methane to elemental carbon under the anaerobic oxidation of methane. Meanwhile, this reaction results in local acidification of the solution inside the pyrite tubes, which favors marcasite lamellae growth on the host pyrite substrate. (C) 2014 Elsevier Ltd. All rights reserved.
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