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现代地质 ›› 2008, Vol. 22 ›› Issue (3): 407-414.

• 岩石学与地球化学 • 上一篇    下一篇

南海沉积物中烃类气体(酸解烃)特征及其成因与来源

祝有海1,吴必豪1,罗续荣1,张光学2   

  1. 1中国地质科学院 矿产资源研究所,北京 100037;2广州海洋地质调查局,广东 广州 510075
  • 收稿日期:2008-02-14 修回日期:2008-04-25 出版日期:2008-03-20 发布日期:2008-03-20
  • 作者简介:祝有海,男,研究员,1963年出生,矿床地质学专业,主要从事天然气水合物和海洋地质的研究工作。
  • 基金资助:

    国家自然科学基金项目(40473001);国土资源部公益性行业科研专项(200811014)

Geochemical Characteristics of Hydrocarbon Gases and Their Origin from the Sediments of the South China Sea

ZHU You-hai1, WU Bi-hao1, LUO Xu-rong1, ZHANG Guang-xue2   

  1. 1Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037,China;
    2Guangzhou Marine Geology Survey, Guangzhou, Guangdong 510075, China
  • Received:2008-02-14 Revised:2008-04-25 Online:2008-03-20 Published:2008-03-20

摘要:

烃类气体是形成天然气和天然气水合物的物质基础,可通过顶空气、吸附烃和酸解烃等方法来探测。南海473个站位767件沉积物样品的酸解烃分析结果表明,甲烷含量为0.8~22 153.6 μl/kg,平均为335.8 μl/kg,并可分成台西南—东沙、笔架南、琼东南—西沙海槽、中建南—中业北、万安—南薇西和南沙海槽等6大异常区,其中南沙海槽是异常最强烈的地区,台西南盆地次之。154件甲烷样品的碳同位素分析结果表明,其δ13C1值为-101.7‰~-24.4‰(PDB标准,下同)〗,平均为-44.5‰,其中南沙海槽的δ13C1值明显偏低,为-101.7‰~-71.4‰,应是微生物气或是以微生物气为主的混合气,而南海其他地区的δ13C1值相对较高,为-51.0‰~-24.4‰,明显属于热解气。

关键词: 酸解烃, 甲烷, 稳定同位素, 气体成因, 南海

Abstract:

Hydrocarbon gases from sediments are the resources to form natural gas and gas hydrate,  which could be measured by headspace gas, absorbed gas, and “extraction” gas(which released by acid treatment of the sediments). Total 767 samples of sediments from 473 stations were collected from the South China Sea, and were treated with acid to determine the concentrations of hydrocarbon gases. The methane concentrations range from 0.8 to 22,153.6 μl/kg with averagely 335.8 μl/kg, and six anomalous areas of higher methane concentrations are subdivided in the South China Sea, including the Taixinan Basin and the Dongsha Islands, the Bijianan Basin, the Qiongdongnan Basin and the Xisha Trough, the Zhongjiannan Basin and Zhongyebei Basin, the Wan'an Basin and Nanweixi Basin, and the Nansha Trough. However, the Nansha Trough is of the highest methane concentrations, and the Taixinan Basin is the secondly, respectively. Total 154 samples were been determined for carbon isotopic composition, whose δ13Cvalues of methane range from-101.7‰ to -24.4‰ with averagely -44.5‰(PDB).Furthermore, lower δ13Cvalues of methane(from -101.7‰ to -71.4‰)are observed in the Nansha Trough, which seem to be mainly microbial gas or mixed gas, whereas there are much 〖JP4〗more thermogenic gas in the other areas of the South China Sea, whose higher δ13C values(from -51.0‰ to -24.4‰)are discovered, respectively.

Key words: hydrocarbon gases, methane, stable isotope, gas origin, the South China Sea

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