Enlargement of Pyrite Framboid Size in Sulfate-Methane Transition Zone of Marine Sediments and Its Implying of Marine Methane Event
Wang Jiasheng
Song Qiang
Lin Qi
Xu Liyuan
Chen Can
Wang Zhou
Geng Kunlong
Abstract：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>20 μm or core size>12 μm and deviation>3 μm might be used as a critical proxy to indicate the environment of marine methane event.
Keywords：pyrite framboidal sizesulfate-methane transition zonemethane eventanaerobic oxidation of methaneseawater redox environmentsedimentologymineralogy
Publication Date：2025-03-14
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 908-917 )