I-129 and halogen systematics in pore waters from gas hydrates and mud volcanoes: Nankai Trough and Costa Rica Margin

费恩(0550122)的智慧价值：天然气水合物和泥火山与天然气的主要成分甲烷的形成和释放有关。这两种情况(天然气水合物由困在水冰中的甲烷组成，泥火山是富含甲烷的流体的管道)在大陆边缘非常常见，并构成了一个巨大的甲烷储藏库。虽然现在人们普遍认为，天然气水合物中捕获的甲烷所含的碳与所有常规化石燃料储量的总和一样多，甚至更多，但这种甲烷的来源还没有被很好地理解。这项研究使用从天然气水合物和泥火山中收集的含甲烷流体中宇宙产生的碘(碘129)来确定大陆边缘甲烷的来源。这项研究试图确定在两个截然不同的环境中甲烷的来源：日本附近的南开海槽和哥斯达黎加附近的大陆边缘。样本已经在手中，并已由日本和德国的合作者分析了大量互补的地球化学物种。样品的卤素浓度将使用电感耦合等离子体质谱和离子色谱进行分析。宇宙成因碘比率将使用普渡大学PrimeLab的加速器质谱仪系统进行测量。所确定的年龄将与三个潜在的有机物质来源的年龄进行比较，以检查是否：(1)甲烷的形成是局部事件，由当前形成的沉积物中的有机物质主导；(2)甲烷与活动边缘的海洋沉积物俯冲有关；或(3)甲烷是由于覆盖板块中存在古老的有机物质。一旦确定了源岩，将估算源岩和当前位置之间的距离，并将其与活动边缘的流体流动模型联系起来。更广泛的影响：这项研究支持研究生和本科生的培训，以及纽约州一所大学教职员工的研究。一名日本博士后也将参与该项目，并在首席研究员的美国实验室工作，该项目不承担任何费用。该项目是美国、日本和德国机构之间的国际合作，包括参与大学之间的学生和教师交流。

ABSTRACT Fehn (0550122) Intellectual Merit: Gas hydrates and mud volcanoes are related to the formation and release of methane, the main ingredient of natural gas. Both occurrences (gas hydrates consist of methane trapped in water ice, and mud volcanoes are conduits of methane rich fluids) are very common along continental margins and constitute a large reservoir of methane. While it is now well accepted that the amount of methane trapped in gas hydrates contains as much or more carbon than all the reservoirs of conventional fossil fuel combined, the origin of this methane is not well understood. This research uses cosmogenically produced iodine (iodine 129) in methane-bearing fluids collected from gas hydrates and mud volcanoes to age date the sources of methane in continental margins. This research seeks to identify source formations for methane in two contrasting environments: the Nankai Trough off Japan and the continental margin off Costa Rica. Samples are already in hand and have been analyzed for a large number of complementary geochemical species by collaborators in Japan and Germany. Halogen concentrations of the samples will be analyzed using ICP-MS and ion chromatography. Cosmogenic iodine ratios will be measured using accelerator mass spectrometry system of PrimeLab, Purdue U. The determined ages will be compared to those of the three potential sources of organic material to examine if: (1), the formation of methane is a local event, dominated by the presence of organic material in currently forming sediments, (2) methane is related to the subduction of marine sediments in active margins; or (3) methane is due to the presence of old organic material in the overriding plate. Once the source formations have been determined, distance between source and current location will be estimated and related to models of fluid flow in active margins. Broader Impacts: This research supports graduate and undergraduate student training, as well as the research of a faculty member at a university in New York State. A Japanese postdoc will also participate in the project and work in the US lab of the principal investigator at no cost to the program. The project is an international collaboration between US, Japanese, and German institutions and includes exchanges of students and faculty between the participating universities.