Methane seepage patterns during the middle Pleistocene inferred from molybdenum enrichments of seep carbonates in the South China Sea
Methane seepage patterns during the middle Pleistocene inferred from molybdenum enrichments of seep carbonates in the South China Sea
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南海渗流碳酸盐岩钼富集推断中更新世甲烷渗流模式
DOI：
10.1016/j.oregeorev.2020.103701
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发表时间：
2020-10
影响因子：
3.3
通讯作者：
Zhu Jiang
中科院分区：
文献类型：
--
作者：
Deng Yinan;Chen Fang;Hu Yu;Guo Qingjun;Cao Jun;Chen Hong;Zhou Jianhou;Jiang Xuexiao;Zhu Jiang
富含甲烷的流体沿世界大陆边缘广泛渗透。甲烷的强烈渗漏可能导致这种强大的温室气体排放到水圈和大气中，这对理解过去剧烈的海洋环境变化和全球变暖具有重要意义。然而，由于古代冷渗漏的剧烈渗透，含硫化物的底部水的缺氧环境仍未确定。本文报道了南海长岩心渗渗碳酸盐岩的微量元素地球化学和相关矿物学及碳氧同位素数据。甲烷渗漏事件的三个不同阶段可能是由天然气水合物的解离引起的。海洋同位素第5阶段（MIS5）第2阶段形成的碳酸盐主要以文石形式存在，钼（Mo）含量极高（可达118 μg/g），自生Mo相对于铀有较强的富集。这些结果表明，由于甲烷的密集渗漏，硫化物底水产生了间歇性甚至永久性的缺氧条件。相比之下，矿物组成和微量元素模式表明，在MIS 5（阶段1和阶段3）之前和之后的碳酸盐形成于硫化物条件下，限制在孔隙水中，甲烷通量相对较低。我们的研究结果强调了极强烈的甲烷渗漏可能导致局部缺氧环境。推断出的富氧环境表明，在MIS 5期间，南海天然气水合物的大规模解离引发了大量甲烷释放到水柱中，这比之前的估计要多。
Seepage of methane-rich fluids, are widespread along the continental margins of the world. Intense seepages of methane may lead to the emission of this powerful greenhouse gas into the hydrosphere and atmosphere with implications in the understanding of past dramatic marine environment changes and global warming. However, euxinic environments with sulfidic bottom water as a result of vigorous seepages at ancient cold seeps remain unidentified. Here we report trace element geochemistry and associated mineralogical and carbon and oxygen isotopic data in seep carbonates collected from long drill cores in the South China Sea. Three distinct stages of methane seepages events probably caused by the dissociation of gas hydrates are discernible. Carbonates formed in stage 2 during the Marine Isotope Stage 5 (MIS5) are mainly occurred as aragonite and show extremely high molybdenum (Mo) contents (up to 118 μg/g), and strong enrichments of authigenic Mo in relative to uranium. These results suggest the presence of intermittent or even permanent euxinic conditions generated by sulfidic bottom water that result from intensive methane seepages. In contrast, mineral compositions and trace element patterns indicate that the carbonates before and after the MIS 5 (stages 1 and 3) form within sulfidic conditions restricted to pore water under relatively lower methane fluxes. Our results highlight extremely intense methane seepages that may potentially result in localized euxinic environments. The inferred euxinic environments imply more amount of massive methane release into the water column than a previous estimation, which was triggered by large-scale dissociation of gas hydrates in the South China Sea during MIS 5.
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影响因子：
3.7
作者：
A. Peketi;A. Mazumdar (corresponding author);R. K. Joshi;D. J. Patil;P. L. Srinivas;A. M. Dayal
通讯作者：
A. Peketi;A. Mazumdar (corresponding author);R. K. Joshi;D. J. Patil;P. L. Srinivas;A. M. Dayal
影响因子：
2.9
作者：
Kerstin Nöthen;S. Kasten
通讯作者：
Kerstin Nöthen;S. Kasten
影响因子：
12.1
作者：
R. Hesse
通讯作者：
R. Hesse
利用碳氢化合物渗漏中的自生碳酸盐中的铁形态来追踪可变的氧化还原条件
影响因子：
4.2
作者：
Chen Linying;Zheng Guodong;Peckmann Jorn;Chen Duofu
通讯作者：
Chen Duofu
影响因子：
2.4
作者：
D. Feng;Duofu Chen;J. Peckmann
通讯作者：
D. Feng;Duofu Chen;J. Peckmann