Geophysical site survey for drilling into a sedimented shallow-water hydrothermal system

钻探沉积浅水热液系统的地球物理现场调查

• 批准号: 503751267
• 负责人: Professor Dr. Thomas Pichler
• 金额: --
• 依托单位: Fachgebiet Geochemie und Hydrogeologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2022
• 资助国家: 德国
• 起止时间: 2021-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/503751267?language=en
• 关键词: Geophysical; site; survey; drilling; into

Marine shallow-water hydrothermal systems (MSWHS), as opposed to deep-sea hydrothermal systems, occur in shallow-water nearshore settings where they can have a considerable impact on the coastal ocean through discharge of reduced, hot hydrothermal fluids. One of the best-studied MSWHS is located in Paleochori Bay on the south side of Milos Island, which has been the focus of numerous scientific studies. However, despite more than 25 years of research, the subsurface processes and mechanisms that generate hydrothermal fluids with contrasting chemical compositions in Paleochori Bay are unclear. In contrast to most other locations, the MSWHS in Paleochori Bay is covered by sediments (of unknown thickness). Thus, the hydrothermal fluids percolate through the sediment cover before venting into Paleochori Bay seawater at low rates. This would allow for sediment-hydrothermal fluid interaction, which should cause a chemical overprint that obscures the true hydrothermal signal. Hence, it is a viable hypothesis that sediment thickness should be a controlling factor for the final chemical composition of hydrothermal fluids in Paleochori Bay. With this in mind, we propose to conduct a geophysical survey of the sediment cover and to generate a map of its thickness for Paleochori Bay. This map can be combined with existing maps of temperature and element distribution in Paleochori Bay pore fluids to evaluate the impact of sediment thickness on the physicochemical composition of the hydrothermal fluids. This new information will be the basis for collecting sediment cores, which are necessary for addressing the bigger questions and subsequent research for Paleochori Bay, such as, (1) Is the MSWHS a typical arc-hosted epigenetic hydrothermal system. These processes modulate the release fluxes of elements in significant ways and need to be understood to decipher the signatures of deeper-seated reactions. (2) Do sediment thickness and fluid flux rates determine the magnitude that sediment-hosted reactions in the shallow subseafloor play in modifying hydrothermal fluid composition? (3) Are fluid flux rates highest where fault planes come up through the basement?

与深海热液系统相反，海洋浅水热液系统发生在浅水近岸环境中，通过排放还原的热液流体，可对沿海海洋产生相当大的影响。研究得最好的MSWHS之一位于米洛斯岛南侧的古乔里湾，这一直是众多科学研究的焦点。然而，尽管超过25年的研究，地下过程和机制，产生热液流体与对比化学成分在古乔里湾尚不清楚。与大多数其他地点相比，Paleochori湾的MSWHS被沉积物（厚度未知）覆盖。因此，热液流体渗透通过沉积物覆盖物排放到Paleochori湾海水之前，在低利率。这将使沉积物-热液流体相互作用，这将造成化学叠加，掩盖真正的热液信号。因此，这是一个可行的假设，沉积厚度应是一个控制因素的最终化学成分的古乔里湾热液。考虑到这一点，我们建议进行地球物理调查的沉积物覆盖，并生成一个地图，其厚度为Paleochori湾。这张图可以与现有的古乔里湾孔隙流体的温度和元素分布图相结合，以评估沉积物厚度对热液流体的物理化学组成的影响。这些新的信息将是收集沉积物岩心的基础，这是解决更大的问题和随后的研究古乔里湾，如：（1）MSWHS是一个典型的弧托管后生热液系统所必需的。这些过程以重要的方式调节元素的释放通量，需要理解这些过程以破译更深层次反应的特征。(2)沉积物厚度和流体通量率是否决定浅海底下沉积物承载的反应在改变热液流体成分方面发挥的作用？(3)在断层面通过基底向上的地方，流体流动速率最高吗？