| 南海东北部岩芯沉积物磁性特征及对甲烷事件的指示 |
| |
| 引用本文： | 林荣骁,王家生,苏丕波,林杞,孙飞,杨军霞.南海东北部岩芯沉积物磁性特征及对甲烷事件的指示[J].沉积学报,2017,35(2):290-298. |
| |
| 作者姓名： | 林荣骁 王家生 苏丕波 林杞 孙飞 杨军霞 |
| |
| 作者单位： | 1.生物地质与环境地质国家重点实验室, 武汉 430074; |
| |
| 基金项目： | 国家自然科学基金，南海天然气水合物成矿理论及分布预测研究专题(GZH20110030-50603)[National Natural Science Foundation of China |
| |
| 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。
|
| 关 键 词： | 磁化率 自生黄铁矿 甲烷渗漏事件 南海东北部 沉积物 |
| 收稿时间： | 2016-04-19 |
Characteristics of Magnetic Susceptibility of Cored Sediments and Their Implications for the Potential Methane Events in Northern South China Sea |
| |
| Institution: | 1.State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;2.Faculty of Earth Science, China University of Geosciences, Wuhan 430074, China;3.Fuzhou Ocean and Fisheries Technology Center, Fuzhou 350026, China;4.Guangzhou Marine Geological Survey, Guangzhou 510075, China |
| |
| Abstract: | In marine methane seepage areas,sedimentary magnetic susceptibility was characterized by abnormally low values,which was related to the formation of authigenic minerals resulted from the anaerobic methane oxidation (AOM) within the sulfate-methane transition zone (SMTZ).In this study,400 sedimentary core samples from Site DH-CL11,Site973-2 and Site973-4 drilled in the northern South China Sea were measured.In connection with the relative content and the sulfur isotopic values of the authigenic pyrites handpicked from the aforementioned 3 sites,the variation characteristics of sedimentary magnetic susceptibility and its indication for methane seep events at the potential gas hydrate areas in the northern South China Sea were discussed.At Site DH-CL11,sedimentary magnetic susceptibility first significantly decreased and then abnormally increased within the paleo-SMTZ (705.5～765.5 cmbsf),which is probably related to the depth change of the SMTZ.At Site 973-2,sedimentary magnetic susceptibility showed a decreasing trend within the paleo-SMTZ (453 ～ 492.5 cmbsf).Greigites were discovered under the SMTZ,which may be related to frequent changes of the SMTZ or the anaerobic oxidation of authigenic pyrites.At Site 973-4,sedimentary magnetic susceptibility significantly decreased within the paleo-SMTZ (584.5～ 878 cmbsf),which was considered to be resulted from methane seep events.In general,these results show that under the methane seepage environments,HS-produced by AOM reacts with magnetic minerals in sediments,resulting in the dissolution of magnetic minerals coupled with precipitation of paramagnetic pyrite,both of which will make an anomalously low MS value in the SMTZ;However,with low HS-concentration,insufficient supply of HS-will lead to partial pyritization,which will result in the preferential formation of greigites followed by secondary magnetic susceptibility signals.Therefore,in gas hydrate prospecting areas,abnormal characteristics of the sedimentary magnetic susceptibility are feasible to indicate deep methane flux variation,thus to show a further indication for the evolution of the underlying gas hydrate occurrence.The abnormal characteristic of sedimentary magnetic susceptibility becomes an indirect but available method to explore gas hydrate occurrence,which is helpful for gas hydrate exploration in the northern South China Sea. |
| |
| Keywords: | magnetic susceptibility authigenic pyrites methane events northeastern SCS sediments |
| 本文献已被 CNKI 万方数据 等数据库收录！ |
| 点击此处可从《沉积学报》浏览原始摘要信息 |
| 点击此处可从《沉积学报》下载免费的PDF全文 |
|
