南海北部海区海底沉积物中孔隙水的Cl^-和SO_4^(2-)浓度异常特征及其对天然气水合物的指示意义  

Chlorine and Sulfate Concentrations in Pore Waters from Marine Sediments in the North Margin of the South China Sea and Their Implications for Gas Hydrate Exploration

作　　者：蒋少涌[1,2] 杨涛[1,2] 薛紫晨[1,2] 杨竞红[1,2] 凌洪飞[1,2] 吴能友[3] 黄永样[3] 刘坚[3] 陈道华[2,3] 

机构地区：[1]南京大学地球科学系成矿作用国家实验室 [2]南京大学海洋地球化学研究中心,江苏南京210093 [3]广州海洋地质调查局,广东广州510760

出　　处：《现代地质》2005年第1期45-54,共10页Geoscience

基　　金：国家"863"计划研究课题 (2003AA611020 /02); 国家"天然气水合物资源综合评价及勘探开发战略研究"专项项目 (GZHZ200203-04-02)。

摘　　要：报道了中国南海北部海区海底沉积物中孔隙水的Cl-和SO42-质量浓度的变化特征, 圈定了孔隙水中Cl-质量浓度的高值异常区。由于水合物形成过程中的排盐效应, 会使其上覆浅表层沉积物中孔隙水的盐度增高, 因此这些氯离子的高值异常区值得进一步的勘查。对孔隙水中SO42-的质量浓度分析表明, 研究区的一些站位表现出随深度增加SO42-的质量浓度梯度发生明显的变化, 计算的硫酸盐甲烷交接带SMI界面深度均在 10m左右, 与ODP164航次和ODP204航次有天然气水合物的钻孔的SMI界面深度基本吻合, 说明这些站位深部有天然气水合物存在的可能性。This paper reports Cl^- and SO_4^(2-) anion concentrations in pore waters from marine sediments in the north margin of the South China Sea. Our results show that several sites in the north margin of the South China Sea display high chlorinity in pore waters. It is suggested that the salt exclusion effect during hydrate formation will cause a salinity increase of pore waters in the hydrate roof zone and shallow subseafloor sediments due to fluid diffusion. Therefore those sites with elevated chlorinity in the South China Sea deserve a further examination for gas hydrate occurrence. Analysis of sulfate concentrations in pore waters reveals a steep sulfate gradient decrease with depths, and the calculated SMI values are around 10 m, which is similar to the SMI values of those well-known gas hydrate occurrences as revealed by ODP Leg 164 and ODP Leg 204 drilling samples. The data (suggest) that those sites hold a great potential for gas hydrate presence at depths and warranty a further detailed (exploration).

关 键 词：Cl^- SO4^2- 孔隙水 天然气水合物 南海北部海区 

分 类 号：P736.4[天文地球—海洋地质] P74[天文地球—海洋科学]