中文摘要：

出现渗出碳酸盐是为寒冷的典型特征之一渗出在大陆人边缘的地点。碳酸盐记录了充满甲烷的液体的发泄的历史。比作在沉积水接口上形成了的 chemoherm 碳酸盐和碳酸盐人行道，像烟囱渗出碳酸盐在沉积水接口下面在液体水管附近猛抛更好因此记录过去的液体流动和作文的信息。这里像烟囱渗出来自华南海的东北 Dongsha 区域的碳酸盐样品被学习在 seafloor 下面理解有煤气的水合物存款的发泄的液体和他们的潜在的关系的起源和自然。基于出现，形态学，岩石学，矿物学和 C- 和 O- 同位素作文，与现在和过去的底部水温度并且预定甲烷版本事件结合了，氧在方解石和水之间的同位素的分别被用来估计猛抛的液体的平衡 18O 价值。从 56.33 ～ 42.70 V-PDB 并且这样的 13C 价值清楚地证明学习烟囱主要从源於生物的甲烷氧化被导出。猛抛的液体的计算平衡 18O 价值从 1.9 Mea 疨?疨 吗？？

英文摘要：

The occurrence of seep carbonates is one of the characteristic features for cold seep sites at continental margins. The carbonates documented the venting history of methane-rich fluid. Compared to the chemoherm carbonates and carbonate pavements which formed on the sediment-water interface, chimney-like seep carbonates precipitated around fluid conduits below the sedi- ment-water interface therefore better recording information of the past fluid flow and composition. Here the chimney-like seep carbonate samples from the northeastern Dongsha area of the South China Sea were studied to understand the origin and nature of the venting fluids and their potential relationship with gas hydrate deposits underneath the seafloor. Based on the occurrence, morphology, petrology, mineralogy and C- and O- isotope compositions, combined with present and past bottom water temperatures and the timing of methane release events, the oxygen isotopic fractionation between calcite and water were used to estimate the equilibrium δ^18O values of the precipitating fluids. The δ^13C values ranging from -56.33‰ to -42.70‰ PDB and thus clearly show that the studied chimneys were mainly derived from biogenic methane oxidation. The calculated equilibrium δ^18O values of the precipitating fluids ranged from 1.9‰ ±0.3‰ to 0.6‰ ±0.3‰ V-SMOW, with an average of 1.4‰ ± 0.3‰ V-SMOW which is heavier than those of seawater even at the last glacial maximum. It is considered that the formation of chimney-like carbonates was closely related to methane hydrate dissociation in the area. The methane hydrates contributed as much as 45.7% of water to the venting fluids. It is suggested that the climate and environmental changes （e.g. sea-level lowering, down-cutting canyons and mass wasting） are the major mechanisms maybe responsible for the destabilization of methane hydrates in the study area. The extensive occurrence of seep carbonates indicates that a large amount of the methane released from methane hydrate dissociation has bee