Bottom-simulating reflectors were observed beneath the southeastern slope of the Dongsha Islands in the South China Sea, raising the potential for the presence of gas hydrate in the area. We have analyzed the chemical and isotopic compositions of interstitial water, headspace gas, and authigenic siderite concretions from Site 1146. Geochemical anomalies, including a slight decrease of chlorine concentration in interstitial water, substantial increase of methane concentration in headspace gas, and 18O enrichment in the authigenic siderite concretion below 400 meters below seafloor are probably caused by the decomposition of gas hydrate. The low-chlorine pore fluids contain higher molecular-weight hydrocarbons and probably migrate to Site 1146 along faults or bedded planes.
1Zhu, Y., Huang, Y., Matsumoto, R., and Wu, B., 2003. Geochemical and stable isotopic compositions of pore fluids and authigenic siderite concretions from Site 1146, ODP Leg 184: implications for gas hydrate. In Prell, W.L., Wang, P., Blum, P., Rea, D.K., and Clemens, S.C. (Eds.), Proc. ODP, Sci. Results, 184 [Online]. Available from: World Wide Web: <http://www-odp.tamu.edu/publications/184_SR/202/202.htm>. [Cited YYYY-MM-DD]
2Institute of Mineral Resources, Chinese Academy of Geological Sciences, 100037 Beijing, People's Republic of China. Correspondence author: zyh@mx.cei.gov.cn
3Guangzhou Marine Geological Survey, Ministry of Land and Resources, 510760 Guangzhou, People's Republic of China.
4Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan.
Initial receipt: 10 August 2001
Acceptance: 18 December 2002
Web publication:
8 April 2003
Ms 184SR-202