Geochemical tracers to establish the significance and timing of gas hydrate induced slide failure in the Hikurangi margin, as a component of the SLAMZ project

本项目研究新西兰东北部Hikurangi边缘滑坡与天然气水合物形成的关系。海底山体滑坡造成重大社会经济危险，不仅是因为它们可能破坏近海设施(如水下电缆)的稳定，更重要的是因为这种斜坡坍塌引发的海啸已造成重大人员伤亡和沿海基础设施的破坏。新西兰近海的Hikurangi边缘非常适合研究各种已知的过程，这些过程是斜坡破坏的驱动因素/预调节因素。该项目将评估许多因素对斜坡稳定性的重要性，包括天然气水合物、沉积物成分和成岩作用(例如，是什么使特定的沉积层变弱)；构造应力和几何形状(例如，斜坡变陡)；以及边缘水文地质(例如，与气候和断层有关的瞬时孔压变化)。该项目的地球化学成分补充了一个由德国牵头的名为新西兰Hikurangi边缘滑动活动(SLAMZ)的大型国际多年项目。这项研究的结果将用来检验目前关于天然气水合物对斜坡稳定性的作用的各种想法，还将解决边缘地区的水和碳收支以及沉积物中流体流动的存在和范围等问题。因此，在我们对全球俯冲带的水文地质、元素循环和地震发生的理解的背景下，这些结果将具有更广泛的相关性。该项目包括培训一名本科生以及指导一名博士后研究人员。海底斜坡破坏是世界各地海洋边缘的一个主要沉积过程，其后果包括边缘建筑、水文地质学和海啸发生。许多研究表明，天然气水合物在控制斜坡崩塌起始和质量运动过程中发挥着重要作用，包括一种新的假设，即天然气水合物本身可能通过类似于陆地环境中的岩石冰川的非常缓慢的可塑性(蠕动)变形而导致海底减弱。与Hikurangi边缘现有的大量地球物理和近海底数据集相比，缺乏深部核心地球化学数据来解决斜坡稳定性中流体、温度和天然气水合物动力学之间的相互依赖关系。该项目旨在与德国和新西兰的科学家合作，生成第一套关于地球化学参数的数据集，以补充正在进行的地球物理、岩石物理和建模工作，以揭示天然气水合物在Hikurangi边缘斜坡稳定性中的作用。SLAMZ计划(由不来梅大学领导)将使用海底对八个地点的沉积物进行采样，这些地点的构造环境和几何形状、天然气水合物稳定性、坍塌特征和流体流动具有鲜明的对比。这个大型国际项目的地球化学部分将产生和分析孔隙流体数据，这些数据对以下方面至关重要：1)确定天然气水合物的分布和浓度；2)评估与海山俯冲相关的天然气水合物稳定性的假设变化；3)限制与天然气水合物和沉积物坍塌过程有关的瞬变；以及4)检测和表征流体流动的性质和来源。我们的结果将有助于我们理解含天然气水合物俯冲带中的地球化学和地质力学变化，并对导致斜坡失稳的社会相关过程产生影响。

This project investigates the relationship between landslides and gas hydrate formation on the northeastern Hikurangi margin of New Zealand. Submarine landslides pose a significant socio-economic hazard, not only because they may destabilize offshore installations (e.g. underwater cables), but more significantly because the tsunamis generated by such slope failures have caused significant human fatalities and destruction of coastal infrastructure. The Hikurangi margin off New Zealand is ideally suited to study the various processes known to act as drivers/preconditioners for slope failure. The project will assess the importance of many factors on slope stability including gas hydrates and sediment composition and diagenesis (e.g., what makes a particular sedimentary layer weak); tectonic stress and geometry (e.g., slope steepening); and margin hydrogeology (e.g., transient pore pressure changes associated with climate and faulting). The geochemical component of this project complements a large, international, multi-year German-led project termed Slide Activity on the Hikurangi Margin, New Zealand (SLAMZ). Results from this study will serve to test various current ideas on the role of gas hydrate on slope stability, and will also address issues such as the water and carbon budgets along the margin and the presence and extent of fluid flow within the sediments. The results will thus have a broader relevance in the context of our understanding of the hydrogeology, element cycling, and earthquake generation in subduction zones worldwide. The project includes the training of an undergraduate student as well as mentoring of a postdoctoral investigator.Submarine slope failure is a major sedimentary process along ocean margins worldwide, with consequences that include margin architecture, hydrogeology and tsunamogenesis. Numerous studies have proposed that gas hydrates play a major role in controlling slope failure initiation and mass-movement processes, including a new hypothesis that postulates that gas hydrate itself may lead to seafloor weakening through plastic, very slow (creeping) deformation similar to rock glaciers in the terrestrial environment. In contrast to the extensive geophysical and near-seafloor data sets available for the Hikurangi margin, there is a lack of deep core geochemical data to address the interdependence of fluid, temperature, and gas hydrate dynamics in slope stability. This project aims at generating the first data set on geochemical parameters that complements ongoing geophysical, petrophysical and modeling efforts to unravel the role of gas hydrate in slope stability of the Hikurangi Margin in a partnership with scientists from Germany and New Zealand. The SLAMZ program (led by the University of Bremen) will use a seafloor to sample sediment at eight locations with contrasting tectonic settings and geometries, depth of gas hydrate stability, slump characteristics and fluid flow. The geochemical component of this large international project will generate and analyze pore fluid data that are key to: 1) Establish distribution and concentration of gas hydrate; 2) Evaluate postulated changes in gas hydrate stability associated with seamount subduction; 3) Constrain transients associated with gas hydrate and sediment slumping processes; and 4) Detect and characterize the nature and sources of fluid flow. Our results will contribute to our understanding of the geochemical, and geomechanical transformations in gas-hydrate bearing subduction zones, with implications to the societally-relevant processes that contribute to slope instability.