硫酸盐-甲烷界面与甲烷通量及下伏水合物赋存的关系

硫酸盐-甲烷界面在富甲烷和含天然气水合物的海洋沉积区已经成为一个重要的生物地球化学识别边界.在硫酸盐-甲烷界面之上,沉积物中的硫酸盐因参与分解有机质和甲烷厌氧氧化反应而被消耗,而界面之下沉积物中的甲烷则不断生成,含量逐渐增加.根据该界面附近硫酸盐浓度和甲烷浓度的变化特征,可以判断该区甲烷流体通量的大小,从而指示下伏天然气水合物的可能赋存状况.南海北部陆坡的柱状沉积物孔隙水数据的分析显示,其硫酸盐-甲烷界面埋深比较浅,表明该海域的甲烷通量较高.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,并暗示着该区下伏海底可能有天然气水合物沉积层赋存.

The Relationship of Sulfate-methane Interface, the Methane Flux and the Underlying Gas Hydrate

The sulfate-methane interface is an important biogeochemical identification interface for the areas with high methane flux and containing gas hydrate. Above the sulfate-methane interface, the sulfate concentration in the sediment is consumed progressively for the decomposition of the organic matter and anaerobic methane oxidation. Below the sulfate-methane interface, the methane concentration increases continuously with the depth. Based on the variation characters of the sulfate and methane concentration around the sulfate-methane interface, it is feasible to estimate the intensity of the methane flux, and thereafter to infer the possible occurrence of gas hydrate. The geochemical data of the pore water taken from the northern slope of the South China Sea show the sulfate-methane interface is relatively shallow, which indicates that this area has the high methane flux. It is considered that the high methane flux is most probably caused by the occurrence of underlying gas hydrate in the northern slope of the South China Sea.