Methane seepage in the Shenhu area of the northern South China Sea: constraints from carbonate chimneys
Methane seepage in the Shenhu area of the northern South China Sea: constraints from carbonate chimneys
复制标题
南海北部神狐海域甲烷渗漏：碳酸盐烟囱的制约
DOI：
10.1007/s00367-016-0438-6
复制
发表时间：
2016
影响因子：
2.1
通讯作者：
Duofu Chen
中科院分区：
文献类型：
--
作者：
Hongxiang Guan;Mei Zhang;Shengyi Mao;Nengyou Wu;Hongfeng Lu;Duofu Chen
在南海北方神狐海域约400 m水深处发现了两个自生碳酸盐烟囱。通过对烟囱体的矿物学、同位素组成和脂类生物标志物的研究，探讨了导致烟囱体形成的地球化学过程。这两个烟囱主要由白云石组成，而内部管道和周围的固结沉积物主要由文石和方解石组成。特定的生物标志物模式（脂质的分布及其贫化的δ 13 C值）表明，甲烷氧化古菌ANME-1的出现率很低，这是通过甲烷的厌氧氧化形成烟囱的原因。一个显着的输入的细菌/浮游藻类和蓝藻的碳池在沉淀的碳酸盐烟囱的高贡献的短链正构烷烃（69%的总烃）和长链正醇（平均56%的总醇）。碳酸盐混合物的氧同位素组成在富碳酸盐烟囱体中为3.1‰ ~ 4.4‰，在内导管体中为2.1‰ ~ 2.5‰，表明它们是在覆盖末次冰期和间冰期旋回的较长时期内由海水来源的孔隙沃茨沉淀而成的。此外，甲烷和底层海水溶解无机碳的混合物可能是碳酸盐烟囱的碳源。
Two authigenic carbonate chimneys were recovered from the Shenhu area in the northern South China Sea at approximately 400 m water depth. The chimneys’ mineralogy, isotopic composition, and lipid biomarkers were studied to examine the biogeochemical process that induced the formation of the chimneys. The two chimneys are composed mostly of dolomite, whereas the internal onduits and semiconsolidated surrounding sediments are dominated by aragonite and calcite. The specific biomarker patterns (distribution of lipids and their depleted δ13C values) indicate the low occurrence of methanotrophic archaea ANME-1 responsible for the chimneys’ formation via anaerobic oxidation of methane. A significant input of bacteria/planktonic algae and cyanobacteria to the carbon pool during the precipitation of the carbonate chimneys is suggested by the high contributions of short-chain n-alkanes (69% of total hydrocarbons) and long-chain n-alcohols (on average 56% of total alcohols). The oxygen isotopic compositions of the carbonate mixtures vary from 3.1‰ to 4.4‰ in the dolomite-rich chimneys, and from 2.1‰ to 2.5‰ in the internal conduits, which indicates that they were precipitated from seawater-derived pore waters during a long period covering the last glacial and interglacial cycles. In addition, the mixture of methane and bottom seawater dissolved inorganic carbon could be the carbon sources of the carbonate chimneys.