NSFGEO-NERC: Magnetotelluric imaging and geodynamical/geochemical investigations of plume-ridge interaction in the Galapagos

NSFGEO-NERC：加拉帕戈斯群岛羽流-山脊相互作用的大地电磁成像和地球动力学/地球化学研究

• 批准号: NE/Z000254/1
• 负责人: Sally Gibson
• 金额: $ 31.7万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2025
• 资助国家: 英国
• 起止时间: 2025 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FZ000254%2F1
• 关键词: NSFGEO; NERC; Magnetotelluric; imaging; geodynamical; NSFGEO; NERC; Magnetotelluric; imaging; geodynamical

Understanding how melt aggregates in our planet's deep interior, i.e. its mantle, during melting remains a critical and fundamental open question in the Earth Sciences. This has important impliactions for topics as diverse as geodynamics and volcano science. Although the transport of melt in the mantle has been typically modelled as being a diffuse process, a variety of geological, geochemical, experimental and theoretical results suggest that this might occur via a network of channels that are 10s of m to km in width during long-distance (100s of km) lateral melt transport. However, it has been challenging to validate these theoretical models via natural observations and assess the importance of melt channelisation in the mantle across different tectonic settings.One geodynamic setting that provides an ideal natural laboratory to understand this channelised transport of melt is the interaction of mantle plumes with nearby mid-ocean ridges (< 1000 km distance). This is because melts derived from a mantle plume provide a distinct geochemical tracer for tracking melt transport processes. The key observed characteristic of this type of interaction is the presence of linear chains of volcanoes (volcanic lineaments). A classic example is the Wolf-Darwin Lineament in Galápagos, a ~ 200 km long volcanic feature extending from above a region where there is currently melting taking place within a mantle plume located ~ 250 km south of the Galápagos Spreading Centre. In our previous work we find that a variety of geophysical and geochemical observations for the Galápagos lineaments are naturally explained in a model where they overlie a network of volatile- and melt-rich channels connecting the Galápagos plume to the Galápagos Spreading Centre. Such volcanic lineaments are found in other plume-ridge interaction settings worldwide (e.g. Reunion, Easter, and Discovery).We propose to use a combination of newly collected geophysical data and novel geochemical observations of the Galápagos lineaments and the Galápagos Spreading Centre. Specifically, we propose to use an array of ~ 60 state-of-the-art broadband marine instruments, dropped overboard from the research ship, to measure electrical conductivity in sections at depths of ~60 to 100 km along and across the volcanic lineaments and the plume-affected ridge segments. Synthetic modelling demonstrates that the conductivity signals associated with the melt channels that we hypothesize are very likely to be detectable. We will couple the results from the geophysical survey with geodynamical models for Galápagos plume flow towards the ridge in order to test our findings and discern among the different possible melt channelisation mechanisms. Finally, while the geophysical instruments are recording data, we propose to dredge samples of igneous rocks along both the northern Galápagos volcanic lineaments and the lineament-spreading ridge intersections. We will analyse these for their geochemistry in order to constrain the contribution of melts from the mantle plume. This work will lead to significant, if not transformative, advances in our understanding of how mantle plumes generated near Earth's core-mantle boundary interact with 'shallow' tectonic features (mid-ocean ridges), and mantle melt transport processes in general.Furthermore, our work will shed important light on the interaction of deep Earth processes on surface systems. This is because the volcanic lineaments that we believe represent the surface expressions of melt transport in the mantle in the Galapagos are fundamental to the migration of marine species in the eastern Pacific (e.g. whale sharks). Our study will provide important constraints on how these topographic features form on the ocean floor and also their potential long-term influence on marine ecosystems.

了解地球融化期间的融化如何在地球内部的深层内部（即其地幔）中融化仍然是地球科学中的关键和基本的开放问题。对于像地球动力学和火山科学等潜水员的主题，这具有重要的暗示。尽管通常将地幔中熔体的运输模型为弥漫性过程，但各种地质，地球，实验和理论结果表明，这可能是通过长距离（100 s of Km）横向熔体转运的通道网络进行的。然而，通过自然观察结果验证这些理论模型并评估层次跨不同构造环境中熔体通道化的重要性。这是因为源自地幔羽的熔体为跟踪熔体传输过程提供了独特的地球化学示踪剂。这种类型相互作用的关键观察到的特征是火山线性链的存在（火山层）。一个经典的例子是加拉帕戈斯（Galápagos）的沃尔夫·达温（Wolf-Darwin）谱系，长度约200公里长的火山特征，该地区从高于该地区的区域延伸，该地区目前在Galápagos扩展中心以南约250公里内发生熔化。在我们以前的工作中，我们发现，在模型中自然解释了对加拉帕戈斯座位的各种地球物理和地球化学观测，它们覆盖了连接Galápagos羽流到Galápagos蔓延中心的挥发性和融化通道网络。这种火山谱系在全球的其他羽毛岩互动环境中都可以找到（例如团聚，复活节和发现）。我们建议使用新收集的地球物理数据和新型地球化学观测的结合，对加拉帕戈斯群岛和加拉帕戈斯传播中心的新地球化学观察结果。具体而言，我们建议使用〜60个最先进的宽带海洋仪器，从研究船上掉落，以测量沿着火山谱系和沿着羽毛状受影响的山脊的深度约60至100 km的部分中的电导率。合成模型表明，与我们假设的熔体通道相关的电导率信号很可能是可以检测到的。我们将将地球物理调查的结果与Galápagos羽流向山脊流动的地球动力学模型相结合，以测试我们的发现并识别不同可能的熔融通道化机制。最后，尽管地球物理仪器正在记录数据，但我们建议沿加拉帕戈斯北部火山谱系和泛滥的山脊交叉点挖掘出火成岩的样品。我们将分析它们的地球化学，以限制地幔羽的熔体的贡献。这项工作将导致我们对地幔羽流如何产生的理解，即使不是变革性的话，在地球核心披风边界附近如何与“浅”构造特征（中端脊）相互作用，而地幔融化的运输过程总体上。furthermore。furthermore，我们的工作将在地面系统上的深层相互作用中散布着重要的光。这是因为我们认为我们认为代表加拉帕戈斯地幔中熔体转运的表面表达是对东太平洋海洋物种迁移的基础（例如鲸鱼鲨鱼）的基础。我们的研究将对这些地形特征如何在海底形成以及它们对海洋生态系统的潜在长期影响提供重要限制。