海洋沉积物SMTZ带黄铁矿莓球粒径增大现象的甲烷事件意义  

Enlargement of Pyrite Framboid Size in Sulfate-Methane Transition Zone of Marine Sediments and Its Implying of Marine Methane Event

作　　者：王家生 宋强 林杞 许力源 陈粲 王舟 耿坤龙 Wang Jiasheng;Song Qiang;Lin Qi;Xu Liyuan;Chen Can;Wang Zhou;Geng Kunlong(College of Marine Science and Technology&Hubei Key Laboratory of Marine Geological Resources/State Key Laboratory of Geomicrobiology and Environmental Changes,China University of Geosciences(Wuhan),Wuhan 430074,China;National Institute for South China Sea Studies,Haikou 571100,China)

机构地区：[1]中国地质大学(武汉)海洋学院,湖北省海洋地质资源重点实验室,地质微生物与环境全国重点实验室,湖北武汉430074 [2]中国南海研究院,海南海口571100

出　　处：《地球科学》2025年第3期908-917,共10页Earth Science

基　　金：国家自然科学基金项目(Nos.42276068,42302215,42472374).

摘　　要：海洋沉积物或海相地层中莓球状黄铁矿的莓球粒径大小和偏差被广泛应用于推测水体的氧化还原沉积环境.然而,在现代海洋天然气水合物赋存海区沉积物中硫酸盐-甲烷转换带(SMTZ)内,甲烷厌氧氧化作用(AOM)成因的黄铁矿莓球粒径出现异常增大现象.当天然气水合物失稳引起异常多数量甲烷释放时,SMTZ位置可能跃升至沉积柱浅表层、海底甚至海水中,可能引起水体的缺氧、酸化和分层等变化;与此同时,增强的AOM仍会促进沉积物中黄铁矿的莓球粒径异常增大,因此有必要重新评估前人依据黄铁矿莓球粒径推测水体氧化还原环境的判别标准.莓球粒径>20μm或莓球内核粒径平均>12μm、标准偏差>3μm的莓球状黄铁矿可能是海洋“甲烷事件”发生时的产物.Single framboid size and deviation of pyrites in marine sediments or strata have been widely used as a useful proxy to indicate the seawater redox environment.However,our recent data about pyrite framboid size from the modern sediments bearing nature gas hydrate show a tremendous increasing trend in pyrite framboid size within the sulfate-methane transition zone(SMTZ),indicating the anaerobic oxidation of methane(AOM)dominated in SMTZ might play a key role to enhance the enlargement of pyrite framboid size.In case of large methane release caused by dissociation of gas hydrate(so called methane event),the rising SMTZ position would move up to shallow sediment or near seafloor and even into bottom seawater,most likely resulting into some anaerobic and acid environmental changes in bottom seawater.Meanwhile,the enhancing AOM coupled with the methane event will still greatly enlarge the pyrite framboid size in sediments.So in this situation,the traditional critical relationship between the pyrite framboid size and seawater redox environment will be no longer functional and need to be modified.It is proposed that the coupling of average framboid size>20μm or core size>12μm and deviation>3μm might be used as a critical proxy to indicate the environment of marine methane event.

关 键 词：黄铁矿莓球粒径 硫酸盐-甲烷转换带 甲烷事件 甲烷厌氧氧化作用 海水氧化还原环境 沉积学 矿物学 

分 类 号：P67[天文地球—海洋地质]