Abstract Hydrocarbon seeps occur worldwide along continental margins and act as conduits for fluid discharge from the lithosphere to the overlying hydrosphere/atmosphere. The dynamics and rates of hydrocarbon release at cold seeps remain poorly constrained. Seepage enables a variety of processes that alter the seafloor morphology and affect the geochemistry of substrata, supporting diverse and important chemosynthetic communities. Here we merge complementary geochemical (oil fingerprinting), geophysical (deep seismic, subbottom, backscatter, multibeam) and video/imaging (Video Time Lapse Camera, DSV ALVIN video, ROV video, AUV photo surveys) data sets to constrain the pathways and magnitudes of methane fluxes from the source reservoir to the seafloor at a well-studied, prolific seep site, Green Canyon (GC) 600 in the Northern Gulf of Mexico. Oil samples from the reservoir, an active vent, and the sea-surface showed compositional similarities consistent with the plumbing system structure identified in seismic data. Spatial distribution of seep indicators such as bacterial mats, microbial communities, methane derived carbonates, and hydrate outcrops, were then used to quantify the total magnitude of methane potentially sequestered in the study domain. Using a systems approach, we combined published values for methane fluxes with data we collected across various scales and resolutions to compile a methane budget for GC600. The system considered for the methane budget is defined as the movement of methane from the salt ridge to the seafloor-water interface for each seep domain, Birthday Candles and Mega Plume. Total estimated input of methane was 2.8 × 10 8 – 2.2 × 10 9 mol/yr in the Birthday Candles domain, and 2.7 × 10 8 – 2.3 × 10 9 in the Mega Plume domain. The combined total output of the system ranged from 3.2 × 10 5 – 8.2 × 10 5 and 3.2 × 10 6 – 5.2 × 10 6 mol/yr respectively for Birthday Candles and Mega Plume domains, leaving a potential surplus (input minus output) of 2.6 × 10 8 – 2.3 × 10 9 mol/yr. Processes that could balance this budget include accumulation of gas hydrate and sediment free-gas, and the underestimated potential of biological sinks such as methane oxidation.

中文翻译：

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墨西哥湾天然渗漏点的碳氢化合物迁移路径和甲烷预算：Green Canyon 600

摘要 碳氢化合物渗漏发生在世界各地的大陆边缘，并作为流体从岩石圈排放到上覆水圈/大气的管道。冷泉处的碳氢化合物释放动力学和速率仍然受到很大限制。渗流促成了各种改变海底形态和影响地层地球化学的过程，支持多样化和重要的化学合成群落。在这里，我们合并了互补的地球化学（石油指纹）、地球物理（深地震、海底、反向散射、多波束）和视频/成像（视频延时摄影机、DSV ALVIN 视频、ROV 视频、AUV 照片勘测）数据集来限制路径和震级墨西哥湾北部绿色峡谷 (GC) 600 一个经过充分研究的多产渗漏点从源水库到海底的甲烷通量。来自油藏、活动喷口和海面的油样显示出与地震数据中确定的管道系统结构一致的成分相似性。然后使用渗漏指标的空间分布（例如细菌垫、微生物群落、甲烷衍生的碳酸盐和水合物露头）来量化研究领域中可能隔离的甲烷总量。使用系统方法，我们将公布的甲烷通量值与我们在不同尺度和分辨率下收集的数据相结合，以编制 GC600 的甲烷预算。考虑甲烷收支的系统定义为甲烷从盐脊到每个渗流域、生日蜡烛和巨型羽流的海底-水界面的移动。估计的甲烷总输入量为 2.8 × 10 8 – 2。在生日蜡烛域中为 2 × 10 9 mol/yr，在 Mega Plume 域中为 2.7 × 10 8 – 2.3 × 10 9 。系统的总输出范围分别为 3.2 × 10 5 – 8.2 × 10 5 和 3.2 × 10 6 – 5.2 × 10 6 mol/yr，分别用于生日蜡烛和 Mega Plume 域，留下潜在的盈余（输入减去输出） 2.6 × 10 8 – 2.3 × 10 9 摩尔/年。可以平衡这一预算的过程包括天然气水合物和沉积物游离气的积累，以及被低估的生物汇潜力，如甲烷氧化。3 × 10 9 摩尔/年。可以平衡这一预算的过程包括天然气水合物和沉积物游离气的积累，以及被低估的生物汇潜力，如甲烷氧化。3 × 10 9 摩尔/年。可以平衡这一预算的过程包括天然气水合物和沉积物游离气的积累，以及被低估的生物汇潜力，如甲烷氧化。