Gas hydrate destabilization: enhanced dewatering, benthic material turnover and large methane plumes at the Cascadia convergent margin
Gas hydrate destabilization: enhanced dewatering, benthic material turnover and large methane plumes at the Cascadia convergent margin
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DOI：
10.1016/s0012-821x(99)00092-8
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发表时间：
1999-06
影响因子：
5.3
通讯作者：
E. Suess;M. Torres;G. Bohrmann;R. Collier;J. Greinert;P. Linke;G. Rehder;A. Tréhu;K. Wallmann-K.-Wallma
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文献类型：
--
作者：
E. Suess;M. Torres;G. Bohrmann;R. Collier;J. Greinert;P. Linke;G. Rehder;A. Tréhu;K. Wallmann-K.-Wallma
混合甲烷-硫化物水合物和碳酸盐在卡斯卡迪亚辐合边缘的一个增生脊的顶部的海底暴露为路面。这些暴露与含甲烷、含硫化物、氨、4He和同位素轻co2逸出的低盐度流体有关。它们表征了一种新认识到的收敛边缘脱水机制，在这种机制中，深层水合物失稳和自由气体使孔隙水变得新鲜，从而推动流体向上流动。这一过程增加了收敛产生的超压，导致局部脱水速率远远高于没有水合物的其他边缘。液体的排放刺激底栖动物的耗氧量，这比在相同海洋深度通常发现的要高几个数量级。甲烷、硫化氢和氨被喷口生物群氧化，从而增加了周转。从山脊注入的水合物甲烷会产生数百米高、几公里宽的烟羽。大量甲烷在水柱内氧化，形成溶解无机碳池δ13C异常。
Mixed methane–sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the Cascadia convergent margin. Vent fields from which methane-charged, low-salinity fluids containing sulfide, ammonia,4He, and isotopically light CO2escape are associated with these exposures. They characterize a newly recognized mechanism of dewatering at convergent margins, where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward. This process augments the convergence-generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate. Discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths. The enhanced turnover results from the oxidation of methane, hydrogen sulfide, and ammonia by vent biota. The injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide. A large fraction of the methane is oxidized within the water column and generates δ13C anomalies of the dissolved inorganic carbon pool.