南海东北部岩芯沉积物磁性特征及对甲烷事件的指示

发布时间：2018-04-30 11:39

本文选题：磁化率 + 自生黄铁矿　；参考：《沉积学报》2017年02期

【摘要】：在甲烷渗漏海域,沉积物磁化率通常表现出异常的低值特征,这与硫酸盐—甲烷转换带(SMTZ)内甲烷厌氧氧化反应(AOM)的发育而导致的自生矿物的形成作用有关。通过测定南海东北部Site DH-CL11、Site 973-2、Site 973-4三个站位400个岩芯沉积物样品的磁化率,并结合三个站位自生黄铁矿丰度和硫同位素等数据探讨了南海北部天然气水合物潜在区沉积物磁化率的变化特征及其对甲烷渗漏事件的指示意义。结果表明:在甲烷异常渗漏海域,上涌甲烷与下渗硫酸盐在SMTZ内发生AOM反应生成了大量的HS-,造成亚铁磁性矿物大量溶解,同时生成大量顺磁性自生黄铁矿,导致沉积物磁化率的异常降低;但是,在HS-不足时,铁硫化物黄铁矿化不充分,会优先生成胶黄铁矿,进而出现二次磁信号。在天然气水合物潜在海域,沉积物磁化率的异常特征可以反映下部甲烷通量的变化,从而指示下伏天然气水合物藏演化,因此能够成为探测天然气水合物藏的一种间接有效的手段,将有助于我国南海北部海域天然气水合物的勘探。
[Abstract]:In the area of methane leakage, the magnetic susceptibility of sediments usually shows the characteristics of abnormal low value, which is related to the formation of authigenic minerals caused by the development of the anaerobic oxidation reaction of methane (AOM) in the sulphate-methane transition zone (SMTZ). By measuring the magnetic susceptibility of 400 core sediment samples from Site DH-CL11 site 973-2 site 973-4 in the northeast of the South China Sea, Based on the data of authigenic pyrite abundance and sulfur isotope at three stations, the variation characteristics of sediment magnetic susceptibility in the potential area of natural gas hydrate in the northern part of the South China Sea and its indicative significance to methane leakage events are discussed. The results show that AOM reaction between upwelling methane and percolation sulfate in SMTZ produces a large amount of HS-in the abnormal leakage area of methane, which results in the dissolution of ferromagnetic minerals and the formation of a large amount of paramagnetic authigenic pyrite at the same time. However, when HS- deficiency is not sufficient, pyrite of iron sulphide will be formed preferentially, and then secondary magnetic signal will appear. In the potential area of gas hydrate, the anomalous characteristics of sediment magnetic susceptibility can reflect the change of methane flux in the lower part, which indicates the evolution of underlying gas hydrate reservoir. Therefore, it can be an indirect and effective means to detect gas hydrate reservoirs, which will be helpful to the exploration of natural gas hydrate in the northern waters of South China Sea.
【作者单位】：生物地质与环境地质国家重点实验室;中国地质大学(武汉)地球科学学院;福州市海洋与渔业技术中心;广州海洋地质调查局;
【基金】：国家自然科学基金(41472085) 南海天然气水合物成矿理论及分布预测研究专题(GZH20110030-50603)~~
【分类号】：P736.21;P744.4

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