【摘要】 海底缺氧带甲烷氧化作用是一个重要的甲烷生物地球化学过程,已被许多地球化学现象所证实。甲烷缺氧氧化有效地减少了渗漏到海水和大气中的甲烷通量,但目前仅有的数据还不能很好地限定甲烷缺氧氧化在全球甲烷循环和全球碳循环中的作用。甲烷缺氧氧化的机理还存在争议,很可能是一个“反甲烷生成”过程。在许多天然气渗漏发育区域,由于甲烷缺氧氧化作用引起环境碱度的增加而沉淀冷泉碳酸盐岩,在海底表层沉积物中形成块状碳酸盐岩结壳。但冷泉碳酸盐岩生成所需的物理化学和生物地球化学条件在很大程度上还不清楚。数值计算表明,孔隙水中溶解足够量的甲烷、冷泉渗漏强度适中、较小的生物扰动作用有利于冷泉碳酸盐岩的生成,而过高的沉积速率则抑制冷泉碳酸盐岩结壳的生成。因此,海底发育冷泉碳酸盐岩可以指示天然气渗漏系统的演化特征。更多还原

【Abstract】 Anaerobic methane oxidation(AMO)is a globally important biogeochemistry process,which has been identified by sufficient geochemical evidence.Unfortunately,the mechanism of AMO is controversial and may be a reverse-methanogenesis process.So the fundamental understanding of the AMO in the global carbon cycle is still lacking.At many gas vent sites authigenic carbonate precipitates because of release of carbonate alkalinity from the AMO.Carbonate precipitation often induces accumulation of carbonate crust at the sediments surface or within shallow surface sediments.Physical and biogeochemical conditions allowing carbonate crust formation are largely unknown.Carbonate crusts are built under a narrow range of physical,chemical and biological conditions.The simulations show that carbonate crusts in the sediments only form when the fluids contain sufficient dissolved methane,with moderate upward fluid flow velocity and when bioturbation coefficents are low.Moreover,high sedimentation rate inhibit crust formation.Thus,seep carbonates at seafloor are indicators of the evolvement of gas venting system.Based on the recent results of AMO and seep carbonate formation,the authors reviewed mechanism of AMO,relevance to ecology and environmental effect,rate of AMO,kinetics of crust formation and its controls.更多还原