Collaborative Research: High-resolution volcanic stratigraphy and geochemical evolution of the Galapagos Platform

洋岛火山是由地幔的熔岩反复喷发到覆盖的板块上形成的。大多数成熟的海洋岛屿系统包括一个几乎线性的火山链，随着年龄的增长，在一个方向上，由于构造板块迁移到固定的岩浆源。然而，现代的加拉帕戈斯火山位于一个大而浅的火山平台之上，这对于海洋岛屿系统来说是不典型的。这个巨大平台的存在使火山岛能够在更长的时间内保持在陆上，这影响了加拉帕戈斯的生物物种形成。尽管有这种粗略的了解，但对加拉帕戈斯地台的构造、演化或组成知之甚少。因此，本研究的突出目标是确定构成加拉帕戈斯地台的熔岩成分，并将其与地幔源和上覆岛屿的空间异质性联系起来。该项目与英国科学家合作，将在英国的一个实验室进行。研究船，并使用他们的远程操作车辆ISIS对加拉帕戈斯平台进行采样。这项工作是一个机会，与英国科学家合作，在加拉帕戈斯进行多学科海洋学研究。此外，尽管加拉帕戈斯群岛在进化和地理学研究中具有重要意义，而且还建立了教科文组织世界遗产-加拉帕戈斯海洋保护区，但该群岛周围的深海海底生态系统实际上仍未得到探索。该项目将与加拉帕戈斯国家公园、厄瓜多尔海军海洋学研究所和查尔斯达尔文研究站合作，后者是支持该地区科学研究的主要组织。研究生和本科生将在项目期间接受培训。与许多海洋岛屿系统不同，现代加拉帕戈斯群岛位于一个大型火山平台的顶部，与岛屿的陆上部分相比，该平台尚未得到充分研究。这项工作的目标是确定形成加拉帕戈斯地台的熔岩的化学成分，并将这些发现与地幔柱和上覆岛屿的空间异质性联系起来，其总体目标是了解加拉帕戈斯地台与其他海洋岛屿系统（例如，夏威夷）。使用ISIS号和詹姆斯·库克号研究船进行的为期21天的现场项目将致力于从平台边缘沿着广泛的地形中采集深海珊瑚（来自英国NERC资助的提案部分）和相关熔岩，其中许多以前从未采集过。这项研究的美国-国家科学基金组成部分包括对平台边缘不同地点的火山地层进行遥控潜水器取样和地质测绘，沿着对取样熔岩进行全面的岸基地球化学研究。这些研究将有助于调查建造平台所涉及的火山就位过程以及海底平台熔岩与邻近/上覆火山岛之间的地球化学关系。在计划的研究航行期间，将对加拉帕戈斯群岛体积最大的火山部分-加拉帕戈斯台地-进行最全面和最系统的现场取样。结果将测试几个重要的问题，加拉帕戈斯平台：i）是加拉帕戈斯平台的空间和垂直地球化学均匀？ii）地台熔岩、上覆火山岛与加拉帕戈斯群岛整体演化之间的关系。现场计划旨在绘制和采样平台周围的几个地层剖面，并将包括详细的底部观察，多波束测绘和原位岩石采样。随后将进行基于海岸的熔岩地球化学和结构分析，包括测量熔岩的主要和微量元素含量以及放射性同位素比率。研究结果将用于构建平台的地层剖面，并将海底熔岩成分与相邻的、覆盖的岛屿和深水熔岩流进行比较，以生成加拉帕戈斯平台形成的综合模型。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ocean island volcanos are formed from repeated eruption of lavas from the Earth's mantle onto the overriding plate. Most mature ocean island systems comprise a nearly linear chain of volcanoes that increase with age in one direction, due to the tectonic plate migrating over the stationary magmatic source. However, the modern Galapagos volcanoes are situated on top of a large, shallow volcanic platform, which is atypical for an ocean island system. The presence of this massive platform has allowed the volcanic islands to remain subaerial for longer time periods, which has influenced biological speciation in the Galapagos. Despite this cursory understanding, very little is known about the construction, evolution, or composition of the Galapagos Platform. Thus, the outstanding goal of this research is to determine the compositions of lavas that make up the Galapagos Platform and relate them to spatial heterogeneity in the mantle source and the overlying islands. The project is in collaboration with UK scientists and will take place on a U.K. research vessel and use their remotely operated vehicle ISIS to sample the Galapagos Platform. This work represents an opportunity to collaborate with UK scientists on multidisciplinary oceanographic studies in the Galapagos. In addition, the ecosystems of the deep submarine environment around the Galapagos Islands remain virtually unexplored, despite the importance of the archipelago in evolutionary and biogeography studies, and the establishment of the Galapagos Marine Reserve, a UNESCO World Heritage Site. The PIs will collaborate with the Galapagos National Park, the Ecuadorian Navy's Oceanography Institute, and Charles Darwin Research Station, which is the principal organization supporting scientific research in the area. Graduate and undergraduate students will be trained during the project.Unlike many ocean island systems, the modern Galapagos Islands are situated on top of a large volcanic Platform that has been understudied compared to the subaerial portions of the islands. The goal of this work is to determine the chemical compositions of lavas forming the Galapagos Platform and relate those findings to the spatial heterogeneity in the mantle plume and the overlying islands with an overarching goal of understanding how the Galapagos Platform has formed in comparison to other ocean island systems (e.g., Hawaii). The ~21 days on-station field program using the ROV ISIS and the research vessel James Cook will be dedicated to sampling deep-sea corals (from a UK NERC funded portion of the proposal) and associated lavas from a broad spectrum of terrains along the margins of the platform, many never before sampled. The US-NSF component of this research involves ROV-based sampling and geological mapping of the volcanic stratigraphy at various locations along the margin of the Platform along with a comprehensive shore-based geochemical study of sampled lavas. These studies will allow an investigation of the volcanic emplacement processes involved in construction of the Platform and geochemical relationships between the submarine platform lavas and adjacent/overlying volcanic islands. During the planned research cruise, the most comprehensive and systematic in situ sampling of the volumetrically largest volcanic portion of the Galapagos Archipelago, the Galapagos Platform will be conducted. Results will test several important questions about the Galapagos Platform: i) is the Galapagos Platform spatially and vertically geochemically homogenous? ii) what is the relationship between the platform lavas, the overlying volcanic islands, and the overall evolution of the Galapagos Archiplelago. The field program is designed to map and sample several stratigraphic sections around the platform and will include detailed on-bottom observations, multibeam mapping, and in situ rock sampling. This will be followed by shore-based geochemical and textural analysis of lavas; including measuring major and trace element contents and radiogenic isotope ratios of the lavas. The results will be used to construct stratigraphic profiles of the Platform and compare submarine lava compositions to adjacent, overlying islands and deep-water lava flows to produce a comprehensive model for the formation of the Galapagos Platform.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.