Collaborative Research: Evolution of the Tristan-Gough-Walvis Ridge Hotspot System: Age and Composition of Expedition 391/397T Volcanic Basement

合作研究：特里斯坦-高夫-沃尔维斯海岭热点系统的演化：391/397T 探险队火山基底的年龄和成分

• 批准号: 2317552
• 负责人: Nicholas Dygert
• 金额: $ 19.59万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317552&HistoricalAwards=false
• 关键词: Collaborative; Research; Evolution; Tristan; Gough

Hotspots are anomalously warm regions in the Earth’s mantle originating near the core-mantle boundary. They play an important role in plate tectonics as one of the primary drivers of continental break up and the subsequent formation of new oceans. As continental fragments drift apart and new oceans form between the land masses, the influential hotspot persists. This hotspot then creates a series of smaller volcanic eruptions on the new seafloor. These eruptions sample the deep hotspot and, in some cases, the shallow mantle. However, the shallow mantle is not uniform in composition. Instead, it evolves as continents drift apart and new seafloor is created. To better understand the role of hotspots in the creation of new seafloor and how the shallow mantle changes as the ocean basin matures, the International Ocean Discovery Program (IODP) Expeditions 391 and 397T drilled six different underwater volcanoes along the Walvis Ridge in the southern Atlantic Ocean. The Walvis Ridge consists of a line of underwater volcanoes formed by a hotspot during the separation of Africa from South American and the formation of the Southern Atlantic Ocean. Using core samples obtained at the six sites, this project will investigate three main questions. First, how much the upper mantle contributes to Walvis Ridge volcanism? What determines the proportion of upper mantle versus hotspot contribution to Walvis Ridge volcanism? Finally, how does the upper mantle change as the continents drift apart and the southern Atlantic Ocean expands. This project supports collaborations between US and international scientists. It will also fund undergraduate and graduate research by students traditionally underrepresented in geosciences (Native American, Black, LGBTQ, etc.).The overarching goal of this project seeks to better understand the magmatic processes associated with continental rifting and ocean basin formation in the South Atlantic, beginning in the early Cretaceous and continuing through today. To do this, IODP Expeditions 391 and 397T drilled six sites spanning 1200km and ~620m of basaltic basement along the Tristan-Gough-Walvis Ridge (TGW) hotspot track. The drill sites sample a significant spatial and temporal range along the TGW: one site on the Frio Rise (adjacent the African continent), two sites on the Valdivia Bank (cognate with the Rio Grande Rise and formed adjacent to the early mid-Atlantic Ridge), and three guyots on the “trident” that leads to the volcanic islands of Tristan da Cunha and Gough. In collaboration with other members of the science party, this project will conduct a comprehensive geochemical and geochronological study of recovered basaltic core to document the changing geodynamic interactions of the hotspot with the overlying lithosphere as rifting and seafloor spreading progressed. The team will collect a wealth of data, including geochronology (Duncan & Heaton, OSU), whole rock geochemistry (Nelson, TU; Potter & Shervais, USU), mineral and associated melt inclusion chemistry (Potter & Shervais, USU), noble gas abundances and isotopic signatures (Dygert & Scholpp, UTK), oxygen fugacity characterization of lavas (Dygert & Scholpp, UTK), and whole rock Re-Os isotopic compositions (Nelson, TU). The team will use these data to test three hypotheses based on preliminary work: (1) Lava chemistry will evolve geochemically from the Etendeka Large Igneous Province in the NE towards the intraplate oceanic islands of Gough and Tristan de Cunha to the SW, consistent with decreasing magma flux through time and changing melt sources; (2) Magmatic flux varies through time and is tied to the proximity to other geologic features (e.g. spreading ridge, African continent, etc.); and (3) Proximity to the spreading ridge will result in lavas with a higher proportion of MORB-like magma (DMM source) relative to the hotspot source. On a small scale, the high-quality core obtained at the various drilling sites provides a unique window into timing and geochemical variations within an individual seamount as it formed and how that may vary with proximity to the spreading ridge. On a larger scale, this work will provide an unmatched look at how plume-ridge interactions change over time.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.

热点是地球地幔中异常温暖的区域，起源于核心壳边界附近。它们在板块构造中起着重要的作用，这是连续分裂的主要驱动因素之一，随后形成了新海洋。随着连续的碎片散开，陆地之间形成新的海洋，影响的热点仍然存在。然后，这个热点在新的海底上产生了一系列较小的火山喷发。这些喷发采样了深热点，在某些情况下是浅套公园。但是，浅地幔在组成中并不均匀。取而代之的是，随着持续漂移并创造了新的海底，它会发展起来。为了更好地了解热点在新海底创建中的作用，以及随着海洋盆地的成熟，国际海洋发现计划（IODP）探险391和397T如何变化。沃尔维斯山脊由一个由热点与南美洲分离和南大西洋的形成期间由热点形成的水下火山组成。使用在六个站点获得的核心样本，该项目将研究三个主要问题。首先，上地幔对沃尔维斯岭火山的贡献有多大？是什么决定了上地幔与热点对沃尔维斯岭火山的贡献的比例？最后，随着继续延伸的距离，上地幔如何变化，南大西洋膨胀。该项目支持美国与国际科学家之间的合作。它还将为学生传统上的地球科学（原住民，黑人，LGBTQ等）提供的学生提供资金。该项目的总体目标旨在更好地了解与南大西洋的连续裂口和海洋盆地形成相关的岩浆过程。为此，IODP Expeeditions 391和397T钻了六个地点，沿着Tristan-Gough-Walvis Ridge（TGW）热点轨道横跨1200公里和〜620m的玄武岩基底。钻机位点沿TGW沿TGW：Frio上升的一个地点（非洲大陆毗邻），在Valdivia Bank上的两个地点（与Rio Grande上升，并形成在At-Atlantic Ridge早期），以及“ Trident的三个家伙”，在“ Trident”上导致Volcanic Da和Giun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun cun c。该项目与科学党的其他成员合作，将对恢复的基本核心进行全面的地球化学和地质学研究，以记录热点不断变化的地球动力学相互作用，而上层岩石圈的地圈随着裂谷和海底扩散的发展。 The team will collect a wealth of data, including geochronology (Duncan & Heaton, OSU), whole rock geochemistry (Nelson, TU; Potter & Shervais, USU), mineral and associated melt inclusion chemistry (Potter & Shervais, USU), noble gas abundances and isotopic signatures (Dygert & Scholpp, UTK), oxygen fugacity characterization of lavas (Dygert & Scholpp，UTK）和整个岩石同位素组合物（Nelson，tu）。该团队将使用这些数据基于初步工作来检验三个假设：（1）熔岩化学将从NE的Etendeka大火成岩省从地球化学上演变，向Gough和Tristan de Cunha的板岩内海洋岛屿发展，与SW的Tristan de Cunha一起，随着时间的流逝和变化的融化来降低岩浆的变化； （2）随着时间的流逝，岩浆磁通量多样性，并与其他地质特征的接近（例如，扩散山脊，非洲人，非洲和（3）接近散布山脊的距单独的封口形成，以及与扩展山脊的距离可能会变化的，这项工作将无与伦比地观察羽毛岩互动如何随时间变化。该奖项反映了NSF的法定任务，并通过使用该基金会的智力优点和广泛的影响来评估NSF的法定任务。