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海洋沉积系统中较高的甲烷浓度和通量是水合物形成的重要物质基础.向上迁移扩散的甲烷在硫酸盐-甲烷交接带(SMI)与硫酸盐反应生成硫化物矿物.保存在沉积物中的自生硫化物及其硫同位素可以用来有效地指示甲烷通量和SMI深度,进而指示深部水合物形成或存在的可能性.通过对中国南海北部陆坡水合物可能存在区域NH-1孔柱状样岩芯沉积物中硫化物及其硫同位素的研究发现:(1)沉积物中黄铁矿含量较高,矿物颗粒较大;(2)沉积物中酸可挥发性硫化物(AVS)峰值(>2μmol/g)最浅深度位于437.5cm,大于自生黄铁矿相对富集的深度(141.5～380.5cm);(3)在262.5～380.5cm间沉积物中自生黄铁矿中硫同位素δ34S具有显著的正异常值(最大+15‰),其他深度均为数值稳定的负异常;(4)δ34S正异常出现在自生黄铁矿相对富集区.与Jorgensen等对黑海沉积物硫化物的研究结果相比较,这些特征表明研究区域的SMI下边界深度为(或曾经在)437.5～547.5cm,反映了向上迁移扩散的甲烷通量具有(或曾经具有)异常高值.这一结论与蒋少涌等通过孔隙水硫酸盐梯度和刘坚等通过顶空气甲烷异常在研究区邻近海域所获得的结果相吻合.表明研究区海域深部形成或赋存水合物的可能性很大.沉积物中自生硫化物及其硫同位素可用作寻找水合物有效的地球化学指标之一.
Higher methane concentrations and fluxes in marine sedimentary systems are important material bases for the formation of hydrates. Upward migration of diffused methane reacts with sulphate to form sulphide minerals in the sulfate-methane interface (SMI), which is stored in sediments Of authigenic sulfide and its sulfur isotopes can be used to effectively indicate the methane flux and SMI depth, indicating the possibility of the formation or existence of deep hydrates.Through the analysis of the potential NH-1 pore-like columnar samples of the continental slope hydrate in the northern South China Sea The results show that: (1) the content of pyrite in sediments is higher and the mineral particles are larger; (2) the peak value of acid volatile sulfide (AVS) in sediments > 2μmol / g), the shallowest depth is located at 437.5cm, which is greater than the relative enrichment depth of the authigenic pyrite (141.5 ~ 380.5cm). (3) The sulfur isotope δ34S in the authigenic pyrite in the sediment from 262.5 to 380.5cm has Significant positive anomalies (up to + 15 ‰), and other depths are negative and negative values of numerical stability. (4) Positive δ34S anomalies occur in the relatively enriched area of authigenic pyrite. Studies with Jorgensen et al. On sulphide in the Black Sea sediments Compared with the results, these characteristics indicate the research The SMI lower boundary depth of the domain is (or formerly) 437.5 ~ 547.5 cm, which indicates that the methane flux upwardly migrated and diffused has (or has had) abnormally high values. This conclusion is consistent with that obtained by Jiang Shaoyong et al. Through pore water sulfate gradients and Liu Jian Etc. are consistent with the results obtained from the abnormal methane in the top air in the adjacent area of the study area, indicating that there is a high possibility of formation or hydrate formation in the deep area of the study area. The spontaneous sulfide and its sulfur isotopes in the sediments can be used to find hydration One of the effective geochemical indicators.