中文摘要：

天然气水合物分解释放的甲烷向上逸散与孔隙水中硫酸盐发生甲烷厌氧氧化—硫酸盐还原反应。深海沉积物有机质氧化也可驱动硫酸盐还原反应。针对甲烷渗漏背景下硫酸盐还原的不同驱动模式,对沉积物中总有机碳、总硫、酸可挥发性硫（AVS）、δ^34pyrite及孔隙水中的SO2-4等进行了测试,结果表明：1总硫在390cm、610-890cm处为0.3%-0.7%,此含量高于相邻层位;2AVS含量在表层较低,于610-868cm区间缓增至565μmol/g,898cm处AVS含量激增至9 315μmol/g;3δ^34pyrite值由浅至深逐渐增大,由-44.4‰升至17.9‰,后回落到12.6‰;490-900cm区间的SO2-4含量逐渐下降,大于900cm则SO2-4含量变化不大。研究结果显示：研究区存在分别由有机质氧化和甲烷厌氧氧化驱动的2种硫酸盐还原模式;硫酸盐甲烷转换带以总硫、δ^34pyrite等指标为判定因素可分为上、下2部分;研究区SMI深度约为900cm,这一较浅的SMI预示着研究区深部可能存在天然气藏或天然气水合物藏;结合微生物研究结果发现,研究区地球化学特征和微生物的分布存在耦合现象,这对进一步研究甲烷水合物潜在区的生物地球化学循环具有一定的意义。

英文摘要：

In terms of two different driving modes on the background of methane leakage,a series of studies on total sulfur（TS）,acid volatile sulfide（AVS）,δ^34pyriteand SO2-4of seawater have been carried out.The results of above studies showed：（1）The content of TS from 390 cm and 610-890 cm are slightly higher than those from the adjacent layers,varying from 0.3% to 0.7%;（2）AVS slowly increased from 610 cm and reached 565μmol/g at 868 cm,finally soared to 9 315μmol/g at 898cm;（3）δ^34Pyritesincreased gradually from-40.9‰to 17.9‰;（4）The content of SO-24 gradually declined during 90-900 cm,and stabilized where it was under 900 cm.The study shows that：both organic oxidation and anaerobic oxidation of methane can drive sulfate reduction in the study area;sulfate-methane transition zone could be divided into two parts by several factors such as TS andδ^34pyrite.From the distribution of sulfur isotope,AVS and TS,the depth of sulfate-methane interface（SMI）in this area is just over 900 cm.The shallow SMI is a strong signal of gas hydrate reservoir which may exist in the deeper layer of the study area.Combined with the research on microbiology,a coupling phenomenon exists between the regional geochemical conditions and microbial distribution.