Processes of hydrogen genesis during seismic cycles in active fault zones (ProHydroGen)

在本项目中，我们计划使用Tullis Onstott教授（普林斯顿大学）在与Moab Khotsong金矿地表以下3.4 km处的鲁德波特石英岩中的活动断层带相交的约600米钻孔中安装的U型管KASMA设备。该钻孔是ICDP资助的DSeis项目的一部分，用于监测地震引发的原地地球化学和同位素组成沿着微生物活动的变化。我们建议操作的气体监测系统结合U型管KASMA安装，这将提供一个独特的机会，收集样品的最小的改变地质流体和未受污染的断裂气体从一个深活动futureplane.During地震动荡的断裂带，我们预计将有一个地气排放，包括H2，这可能是一个营养源，为深部微生物的生命。地气，特别是H2和O3，将使用直接安装在自动U型管KASMS气体分离器上的便携式气体分析系统的特定传感器进行连续检测。在地震活动前后，我们希望通过对个别流体的化学和同位素特征的分析，阐明产生H2的起源和过程，这依赖于从水中裂解O-H键。结合断裂带的渗透率和孔隙度数据，这一研究将有助于了解流体从其源到目的深度的不同运移机制。它将回答这个问题，如果低地震事件增加孤立的流体的连通性，并提供新的路径已经存在的H2的迁移或暴露新鲜的矿物表面的水-岩石相互作用，并释放新鲜的机械化学合成的H2。直接现场分析的样品获得的U型管将确定如何快速地下气体地球化学的变化发生在地震事件的响应。识别激发地气峰的地震矩以及震源距断层和钻孔的距离和方位的影响，通过采集气样并在实验室进行分析，可以评价H2的H/D同位素组成在多大程度上，和CH 4以及13 CCO 2和13 CCH 4的变化，并验证它们是否来自相同的来源，以及例如这些物质之间的同位素交换是否处于热力学平衡。稀有气体同位素测量将允许计算压裂液的停留时间，并且还将有助于回答测量的H2/He比率是否与计算的H2/He辐射分解/辐射成因产量匹配的问题。从天然气化学测量中获得的数据是描述流体地球化学行为的物理化学模型的重要输入参数，当与地震图相结合时，将更好地限制断层带地下天然气化学生产过程的全球丰度。

In this project, we plan to make use of a U-tube-KASMA device installed by Prof. Tullis Onstott (Princeton University) in a ~600 meter borehole intersecting an active fault zone in the Roodepoort Quartzite located 3.4 km below land surface in the Moab Khotsong gold mine. The borehole is part of the ICDP-funded DSeis project and used to monitor seismically triggered changes in in-situ geochemical and isotopic compositions along with microbial activity. We propose the operation of a gas monitoring system combined with the U-tube-KASMA installation, which will provide the unique opportunity to collect samples of minimal-altered geofluids and uncontaminated fracture gases from a deep active fault plane.During seismic unrest of the fault zone, we anticipate that there will be a geogas discharge including H2 which may serve as a nutrient source for deep microbial life. The geogas and especially H2 and O3 will be detected continuously using specific sensors of a portable gas analytical system directly mounted to the gas separator of the automated U-tube-KASMS. With the chemical and isotopic characterization of the individual fluids before and after seismic activity we hope to clarify the origin and the process generating the H2, which rely on cleavage of O-H bonds from water. In combination with data on the permeability and porosity of the fault zone, this research will help to understand different migration mechanisms of fluids from their source to the target depth. It will answer the question if low seismic events increase connectivity of isolated fluids and provide new pathways for migration of already existing H2 or expose fresh mineral surfaces for water-rock interactions, and release fresh mechano-chemically synthesized H2.Direct on-site analyses of the samples gained by the U-tube will determine just how rapidly changes in subsurface gas geochemistry are occurring in response to seismic events. The identification of seismic moment that provokes geogas peaks and the influence of distance and orientation of the focal point to the fault and the borehole should be identified.By collecting gas samples and analyzing them in the laboratory, we will be able to evaluate to what extent the H/D isotopic compositions of H2, and CH4 as well as 13CCO2 and 13CCH4 change and to verify if they derive from the same sources and if e.g. isotope exchange between these species is in thermodynamic equilibrium. Noble gas isotope measurements will allow for the calculation of residence times of the fracture fluids and will also help to answer the question if measured H2/He ratios match with a calculated H2/He radiolytic/radiogenic production yield. The data derived from gas chemical measurements are important input parameters for physico-chemical models describing the geochemical behavior of fluids, and when combined with seismic maps will better constrain the global abundance of the subsurface gas-chemical production processes in a fault zone.