南海北部陆坡沉积物硫酸盐-甲烷反应界面深度的空间变化及其对甲烷水合物赋存状态差异性的指示意义

Spatial variation in depth of sulfate-methane interface in sediments of the northern slope of the South China Sea and its implication for occurring status of methane hydrate

海洋沉积物中的硫酸盐-甲烷反应界面(SMI)的深度变化能够指示下伏甲烷水合物的赋存状态。本文通过对南海北部陆坡天然气水合物潜在分布区沉积物间隙水化学和自生碳酸盐氧、碳同位素组成资料系统分析和对比,探讨了南海北部陆坡沉积物的SMI深度空间变化对下伏甲烷水合物的赋存状态的指示意义。结果表明,南海北部陆坡沉积物的SMI的深度呈现出从西南-东北变浅的趋势,这一趋势与自生碳酸盐的碳同位素组成揭示的甲烷释放量增大趋势有很好的对应关系,进而表明在南海北部陆坡从西南-东北甲烷水合物的埋藏深度变浅或者甲烷水合物的分解程度增大。

The depth of sulfate-metnane interface （SMI） in sediments could indicate occurring status of methane hy- drate. By systimatically paralell analysis of pore water geochemical data and authgenic cabonate oxygen and carbon isotopic data available from the potential gas hydrate areas of the northern slope of the South China Sea （SCS）, the implication of spatial variation of sulfate-metnane interface in sediments for occurring status of underlying methane hydrate in the northern slope of SCS was discussed. It was illustrated that the SMI in sediments of the northern slope of SCS tends to be shallow from the southwest to the northeast. The spatial variation of SMI exactly corre sponds to accretion of released methane which was indicated by carbon isotope of the authigenic carbonate,implica ting that the buried depth of underlying methane hydrate temds to be shallow, or decomposition of underlying methane hydrate temds to be intensive from the southwest to the northeast.