海洋天然气水合物系统硫同位素研究进展

Research Progresses of Sulfur Isotope in Marine Gas Hydrate Geological System

在海洋天然气水合物的地质系统中,甲烷的渗漏作用形成了独特的地球化学微环境。渗漏的甲烷在硫酸根—甲烷氧化还原界面与硫酸根之间发生厌氧氧化反应,同时硫酸盐发生还原反应,形成具有特殊同位素组成的自生碳酸盐、硫化物(AVS、黄铁矿等)和硫酸盐(重晶石、石膏)等。反应过程中硫酸盐还原菌的作用使得产物中硫的同位素发生了强烈分馏,具体表现为低3δ4S值的硫化物矿物和高3δ4S值的硫酸盐矿物的形成。沉积物中这种独特的硫同位素特征与海洋天然气水合物系统中独特地球化学微环境有关,是硫酸盐还原反应过程中细菌控制的硫酸盐分馏和厌氧细菌对硫的歧化反应(disproportionation)的共同作用结果。

The seeping methane results in a special geological chemical micro-environment in marine gas hydrate geologic system. The anaerobic oxidation and reduction between methane and sulfate at sulfate-methane interface（SMI） induce mass of minerals, such as anthigenic carbonate, sulfides （AVS, pyrite）and sulfates （barite, gypsum）, and so on. Because of the effect of sulfate reduce bacteria, the low δ^34S value of sulfide can compares with the high δ^34S value of sulfate. The occurrence of such fractionation may be the common effect of the kinetic effects governed by the progresses of bacterial sulfate reduction and anaerobic bacterial disproportionation of elemental sulfur.