Collaborative Research: Investigating Mantle Source Reservoirs and Cretaceous Plate Motions Recorded by Ancient Mid-Pacific Oceanic Rises and Seamount Tracks

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。地球表面由许多刚性“板块”组成，这些板块随着高粘性内部地幔的流动而移动。如果将单个板块过去的运动与地球上的固定来源（如所谓的“地幔热点”）进行比较，就可以确定它们的运动。这些热点是由地幔柱产生的，地幔柱是在地核-地幔边界上或附近产生的大量热化学物质。这些热物质的上涌可以在地球表面产生火山活动，当板块在其上移动时，火山活动保持相对静止，产生成分不同的火山链，这些火山链离热点越远，年龄就越老。这项工作，通过追踪几个记录较少的火山链的年龄、组成和形态，试图更好地了解发生在中白垩纪（120-80 Ma）的全球规模板块重组事件的时间和驱动因素。目标地点包括中太平洋地区的Liliuokalani Ridge， Hess Rise和Mid-Pacific Mountains。该团队将能够测试这些特征是否由目前在法属波利尼西亚北部地区的地幔柱形成。然后，结合年龄和化学结果将用于限制大约100 Ma的主要板块重组事件的时间。该项目支持三名早期职业科学家，两名博士和一名硕士研究生。此外，这次航海探险将包括来自内华达州大学拉斯维加斯分校和加州州立大学长滩分校少数民族服务机构的八名本科生研究参与者。该项目包括一个为期31天的海上探险，以疏浚海山，山脊和上升内部和附近的赫斯上升和中太平洋山脉。此外，该团队还将分析美国国家海洋和大气管理局海洋勘探和研究远征队在卡琳岭发现的玄武岩，以及即将到来的鹦鹉螺号远征队在Liliuokalani海底山收集的样本。陆上工作将包括从代表性熔岩流中获得40Ar/39Ar年龄测定和地球化学示踪剂（主要和微量元素；Sr-Nd-Pb-Hf同位素）。这些新的样本和综合数据集将允许测试以下假设：H1) Liliuokalani海山和Hess隆起是由Marquesas地幔柱形成的。H2)皮特凯恩地幔柱是卡琳岭和中太平洋山脉的主要来源。H3)中太平洋山脉记录了白垩纪板块运动变化的时间和方向。H4)中太平洋山脉和赫斯隆起的构造受地幔柱-（远端）脊的相互作用控制，通过软流圈熔体通道的形成。验证这些假设将有助于提高对地幔柱动力学的理解，以及对海洋地貌和大火成岩省建设的“自下而上”控制。此外，绘制地幔柱的长寿命表达式可以让我们对地幔源储层有前所未有的了解，这些储层为热点火山活动提供了动力。地质年代学、化学和形态学的结合将允许在白垩纪正常超时（122-83 Ma）期间显著改进太平洋绝对板块运动模型。该奖项反映了美国国家科学基金会的法定使命，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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Earth’s surface is composed of numerous rigid ‘plates’ that move with the flow of a highly viscous interior mantle. Individual plate movements can be determined if their past motions are compared to a fixed source on Earth, such as so-called “mantle hotspots”. These hotspots are generated by mantle plumes, large thermo-chemical uprisings of material that originate on or near the core-mantle boundary. These upwellings of hot material can produce volcanism on Earth’s surface that remains relatively stationary while plates move over them, generating chains of compositionally distinct volcanoes that are progressively older the further they are from the hotspot. This work, through tracing ages, compositions, and morphologies of several poorly-documented volcanic chains, seeks to better understand the timing and drivers of global scale plate reorganization events that took place in the Mid-Cretaceous (120-80 Ma). The target locations include the Liliuokalani Ridge, Hess Rise and Mid-Pacific Mountains in the Central Pacific region. The team will be able to test whether the features were built by mantle plumes that are currently underlying the Northern French Polynesia region. The combined age and chemistry results will then be used to constrain the timing of a major plate reorganization event at ca. 100 Ma. This project supports three early-career scientists, two PhD, and one MSc student. In addition, the seagoing expedition will include eight undergraduate research participants from the minority serving institutions of University of Nevada, Las Vegas and California State University, Long Beach. The project involves a 31-day seagoing expedition to dredge seamounts, ridges and rises within and near Hess Rise and the Mid-Pacific Mountains. In addition, the team will analyze basalts recovered on NOAA-Ocean Exploration and Research expeditions from Karin Ridge and samples from an upcoming E/V Nautilus expedition to the Liliuokalani Seamounts. Onshore work will include obtaining 40Ar/39Ar age determinations and geochemical tracers (major and trace elements; Sr-Nd-Pb-Hf isotopes) from representative lava flows. These new samples and comprehensive datasets will allow for the testing of the following hypotheses: H1) The Liliuokalani Seamounts and Hess Rise were formed by the Marquesas Mantle Plume. H2) The Pitcairn Mantle Plume is the primary source of the Karin Ridge and Mid-Pacific Mountains. H3) The Mid-Pacific Mountains record the timing and orientation of Cretaceous plate motion changes. H4) The structure of the Mid-Pacific Mountains and Hess Rise are controlled by plume – (distal) ridge interaction through the generation of asthenospheric melt channels. Testing these hypotheses will lead to an improved understanding of mantle plume dynamics and ‘bottom-up’ controls on oceanic geomorphology and large igneous province construction. Furthermore, mapping the long-lived expressions of mantle plumes allows for unparalleled insight into the mantle source reservoirs that feed hotspot volcanism. The combination of geo-chronology, chemistry and morphology will allow for a significantly improved Pacific absolute plate motion model during the Cretaceous Normal Superchron (122-83 Ma).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.