Collaborative Research: Early Evolution of the Hawaiian Plume from the Geochemistry and Geochronology of Basalts Spanning the Entire Emperor Seamount Chain

合作研究：横跨整个皇帝海山链的玄武岩地球化学和地质年代学夏威夷羽流的早期演化

• 批准号: 2135692
• 负责人: Aaron Pietruszka
• 金额: $ 52.05万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-15 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2135692&HistoricalAwards=false
• 关键词: Collaborative; Research; Early; Evolution; Hawaiian

The Hawaiian-Emperor Chain is one of the longest (6,000 km), largest (6 million cubic km), and most persistently active (100 volcanoes over ~80 million years) hotspot provinces on Earth. The extensive volcanism of the Hawaiian-Emperor Chain is caused by the Hawaiian mantle plume, which rises buoyantly from the core-mantle boundary and produces some of the hottest and most primitive basalt lavas in recent geological time. Studies of the Hawaiian-Emperor Chain have led to major discoveries and concepts of critical importance to the Earth Sciences, including plate tectonics and the nature of compositional heterogeneity in the deep mantle. The Emperor Seamounts are the oldest, least studied, and most enigmatic portion of the Hawaiian-Emperor Chain. This project is a detailed geochemical (lava chemistry) and geochronological (age determination) study that will resolve the temporal progression of the Emperor Seamounts and the origin of their unusual basalt compositions compared to the Hawaiian Islands. The results of this study will facilitate testing of controversial models on the early dynamics of the Hawaiian mantle plume and its relationship to the history of Pacific plate tectonics. An integrated summer program for local high school and community college students will be initiated as part of this project. The long-term goal of this summer program is to increase the number and diversity of local (especially Native Hawaiian and Pacific Islander) college students in STEM by exposing them to the (1) exciting range of careers in the Geosciences and (2) the profound impact that Earth processes have on the Hawaiian Islands and people (e.g., volcanic eruptions, earthquakes, landslides, and seasonal flooding).This project will examine the temporal-compositional evolution of the oldest (~80-50 Ma) and most enigmatic volcanoes of the Hawaiian-Emperor Chain using the geochemistry (major and trace elements, and Pb-Sr-Nd-Hf isotope ratios) and geochronology (40Ar/39Ar incremental heating) of Emperor Seamount basalts. The major goals are 1) to delineate the transition of the Hawaiian mantle plume from a near-ridge environment to the recent style of upwelling that is far from plate boundaries and 2) improve understanding of Pacific mantle dynamics. The research will answer six key questions: (1) Why are basalts from Detroit Seamount so depleted? Basalts from Detroit, the second oldest Emperor Seamount (~81-76 Ma), are compositionally depleted; some are identical to Pacific mid-ocean ridge basalts (MORB). Two models for Detroit basalts will be tested: (a) entrainment of the ambient depleted Pacific upper mantle into the Hawaiian plume or (b) melting of a depleted lower mantle component—intrinsic to the Hawaiian plume—to an unusually high degree and shallow depth. These depleted mantle models are each consistent with Pacific plate reconstructions that suggest Detroit formed on young, thin oceanic lithosphere near the axis of a mid-ocean ridge. (2) How old is Meiji Seamount? Tholeiitic basalts from Meiji, the oldest Emperor Seamount, will be used to constrain a major tectonic shakeup in the Pacific basin and the earliest known influence of the depleted Detroit mantle component on the composition of Hawaiian-Emperor Chain basalts. (3) Has the age progression of the Emperor Seamounts varied? Geodynamic models suggest that the Hawaiian-Emperor bend was caused by the rapid southward motion of the Hawaiian plume rather than an abrupt change in Pacific plate motion. New dating of basalts from the Emperor Seamounts will be used to nail down the migration rate and provide context for future geodynamic models. (4) What is the distribution of the depleted Kea- and Detroit-types of mantle heterogeneities along the Emperor Seamounts? A detailed temporal-spatial map of basalt chemistry will help to constrain models for the early dynamics of the Hawaiian plume. Does a top-down (5) or bottom-up (6) geodynamic model best explain these temporal-spatial-compositional trends? The trace element and isotopic map will be used to distinguish an upper vs. lower mantle origin for the Detroit component. A top-down model (e.g., plume-ridge interaction or plume capture by a mid-ocean ridge) would be supported by an upper mantle origin, whereas a bottom-up model (e.g., mantle wind) would be supported by a lower mantle (i.e., plume) origin.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.

夏威夷-皇帝链是地球上最长（6,000 公里）、最大（600 万立方公里）和最持续活跃（约 8000 万年里有 100 座火山）的热点省份之一。是由夏威夷地幔柱引起的，它从核心-地幔边界浮力上升，产生了近代地质中一些最热、最原始的玄武岩熔岩。对夏威夷-皇帝链的研究带来了对地球科学至关重要的重大发现和概念，包括板块构造和深部地幔成分异质性的本质。皇帝海山是最古老、研究最少且最多的。该项目是一项详细的地球化学（熔岩化学）和地质年代学（年龄测定）研究，将解决皇帝海山的时间演变及其不寻常的起源。这项研究的结果将有助于测试有关夏威夷地幔柱的早期动力学及其与太平洋板块构造历史的关系的有争议的模型。作为该项目的一部分，该暑期项目的长期目标是通过让当地（尤其是夏威夷原住民和太平洋岛民）大学生接触 (1) 令人兴奋的领域，增加他们在 STEM 中的数量和多样性。的职业生涯地球科学和 (2) 地球过程对夏威夷群岛和人类的深远影响（例如火山爆发、地震、山体滑坡和季节性洪水）。该项目将研究最古老的（~80-50使用地球化学（主要元素和微量元素，以及 Pb-Sr-Nd-Hf 同位素）研究夏威夷-皇帝链上最神秘的火山比例）和皇帝海山玄武岩的地质年代学（40Ar/39Ar增量加热）主要目标是1）描绘夏威夷地幔柱从近山脊环境到远离板块边界的近期上升流类型的转变。 2）提高对太平洋地幔动力学的认识。该研究将回答六个关键问题：（1）为什么底特律海山的玄武岩如此枯竭？ (~81-76 Ma)，成分贫乏；有些与太平洋中脊玄武岩 (MORB) 相同，将测试底特律玄武岩的两个模型：(a) 周围贫乏的太平洋上地幔夹带到夏威夷羽流中。 (b) 耗尽的下地幔成分（夏威夷地幔柱固有的）熔化到异常高的程度和浅的深度。这些耗尽的地幔模型均与太平洋一致。板块重建表明底特律形成于大洋中脊轴附近的年轻薄海洋岩石圈上 (2) 明治海山（最古老的皇帝海山）的拉斑玄武岩将被用来限制重大构造震动。太平洋盆地中已知的最早的耗尽底特律地幔成分对夏威夷-皇帝链玄武岩成分的影响 (3) 具有皇帝海山的年龄进展。地球动力学模型表明，夏威夷-皇帝弯曲是由夏威夷羽流的快速向南运动引起的，而不是太平洋板块运动的突然变化引起的。对皇帝海山玄武岩的新测年将用于确定迁移率和变化。 (4) 沿皇帝海山的贫化基亚型和底特律型地幔异质性的分布情况如何？详细的玄武岩化学时空图将有助于夏威夷羽流早期动力学的约束模型是否可以最好地解释这些时空成分趋势？底特律部分的上地幔起源与下地幔起源将由上地幔起源支持，而自下而上模型则支持自上而下的模型（例如羽流-脊相互作用或大洋中脊捕获的羽流）。 （例如，地幔风）将得到下地幔（即地幔柱）起源的支持。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。