Causes for recent fluid venting at the Cretaceous Henry Seamount, Canary Archipelago

加那利群岛白垩纪亨利海山近期流体排放的原因

• 批准号: 418368213
• 负责人: Privatdozent Dr. Andreas Klügel
• 金额: --
• 依托单位: Fachgebiet Allgemeine Geologie / Marine Geologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418368213?language=en
• 关键词: Causes; recent; fluid; venting; Cretaceous

Hydrothermal circulation of seawater through ageing oceanic crust is globally important for cooling of the lithosphere, chemical exchange between crust and ocean, and marine ecosystems. At sediment-covered old crust, efficient fluid circulation requires basement outcrops, such as seamounts, that form pathways through the impermeable sediment blanket. Only few venting seamounts that are not related to active volcanism have been found so far; these are located on warm and relatively young Pacific crust. The probably first example for an hydrothermally active seamount on old crust is Henry Seamount near El Hierro, Canary Islands. A reconnaissance dredging campaign during R/V METEOR cruise M66/1 yielded samples that indicate Holocene fluid seepage at this seamount, even though the edifice was age dated to 126 million years. In order to discover, document and sample the seepage sites, Henry Seamount was investigated in detail during R/V METEOR cruise M146 in 2018. It was found that large areas of the seamount are covered with shells from vesicomyid clams, which documents relatively recent widespread seepage. Accompanying heat flow measurements, however, showed no respective anomalies. Local sampling of the seafloor by gravity corer and grab yielded, among others, numerous shells and unexpectedly fresh basaltic ash and lapilli, which unequivocally indicates recent volcanic activity of Henry Seamount. In the proposed project we will investigate the basaltic samples with petrological-geochemical methods, determine the ages of the volcanic rocks as well as of the shells, and evaluate hydroacoustic and TV-sled survey data from cruise M146. The aim is to understand causes, extent, and consequences of the inferred fluid seepage at Henry Seamount, and generally an improved understanding of hydrothermal systems at submarine intraplate volcanoes that erupt only rarely.

海水通过老化洋壳的热液循环对于岩石圈冷却、地壳与海洋之间的化学交换以及海洋生态系统具有全球重要意义。在沉积物覆盖的老地壳，要实现有效的流体循环，就需要有海底山脉等露出地面的基底，这些基底形成穿过不透水的沉积层的通道。迄今为止，只发现了少数与活火山活动无关的喷发海山;这些海山位于温暖和相对年轻的太平洋地壳上。加那利群岛耶罗岛附近的亨利海山可能是老地壳上热液活跃海山的第一个例子。在METEOR M66/1号研究船巡航期间进行的一次勘测疏浚活动取得的样本表明，该海山有全新世流体渗漏，尽管该建筑物的年龄可追溯到1.26亿年。为了发现、记录和取样渗漏点，2018年METEOR号R/V M146巡航期间对亨利海山进行了详细调查。据发现，海山的大部分区域覆盖着泡囊蛤的贝壳，这证明了较近期的广泛渗漏。然而，伴随的热流测量没有显示出相应的异常。通过重力取样器和抓斗在当地对海底取样，除其他外，发现了许多贝壳和意外新鲜的玄武岩灰和火山砾，这明确表明亨利海山最近有火山活动。在拟议的项目中，我们将用岩石学-地球化学方法调查玄武岩样品，确定火山岩和贝壳的年龄，并评估M146号巡航的水声和电视雪橇调查数据。其目的是了解原因，程度和后果的推断流体渗漏在亨利海山，并普遍提高认识的热液系统在海底板内火山喷发很少。