东沙海域SMI与甲烷通量的关系及对水合物的指示  

Relationship of Sulfate-Methane Interface(SMI),Methane Flux and the Underlying Gas Hydrate in Dongsha Area,Northern South China Sea

作　　者：邬黛黛[1,2] 吴能友[1,2] 张美[1,2] 管红香[1,2] 付少英[3] 杨睿[1,2] 

机构地区：[1]中国科学院广州能源研究所可再生能源与天然气水合物重点实验室,广东广州510640 [2]中国科学院广州天然气水合物研究中心,广东广州510640 [3]广州海洋地质调查局,广东广州510760

出　　处：《地球科学（中国地质大学学报）》2013年第6期1309-1320,共12页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金(Nos.41003010;41273022);国家重点基础研究发展项目"973"计划(No.2009CB219506);广东省自然科学基金(No.10451007006006008)

摘　　要：硫酸根甲烷界面（SMI）是识别海洋沉积物中天然气水合物赋存（甲烷通量）的一个重要生物地球化学标志．通过对南海北部陆坡东沙海域37个站位浅表层沉积物中孔隙水的SO4^2-和H2S含量变化和沉积物顶空气甲烷含量的变化等地球化学特性进行分析，研究南海北部东沙海域硫酸根甲烷界面（SMI）的分布情况，通过硫酸根变化梯度估算甲烷通量．研究结果显示，东沙海域存在南部深水区“海洋四号”沉积体和北部浅水区九龙甲烷礁两个水合物有利区域，SMI埋深普遍较浅，指示较高的甲烷通量（3．8×10^-3～5．9×10^-3mol／（cm^2·a）），与国际上已发现天然气水合物区的地球化学特征相类似．这种高甲烷通量很可能是由下伏的天然气水合物所引起的，暗示着该区海底之下可能有天然气水合物层赋存．The sulfate-methane interface （SMI） is an important biogeochemical indication for the area with high methane flux and gas hydrate occurrence. In this paper, 37 surface cores were collected in the Dongsha Area of northern South China Sea, and the characteristics of SO4^2- and H2 S concentrations change of the pore water and CH4 concentration change of the head- spaces in the sediments were analyzed. Furthermore, the SMI distribution characteristics were discussed and the methane fluxes were calculated using the sulphate change grades in the Dongsha area of northern South China Sea. The results show that there are two gas hydrate potential areas in the study area. One is the Haiyang-4 site in the southern deep water area, and the other is the Jiulong methane reef in the northern shallow water area. The relatively shallow SMI distribution and high methane flux （3.8× 10 ^-3-5.9×10^-3 mmol/（cm^2 · a）） in the Dongsha area, northern South China Sea are similar to the geochemical characteristics in foreign areas where the gas hydrate occurs. It is convinced that the high methane flux is most probably caused by the occurrence of gas hydrate deposit below the seafloor, which indicates there are gas hydrate reservoirs underneath in the Dongsha area, northern South China Sea.

关 键 词：天然气水合物 甲烷 通量 硫酸根甲烷界面(SMI) 南海 

分 类 号：P67[天文地球—海洋地质]