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

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。地球表面由无数坚硬的板块组成，这些板块随着高度粘性的内部地幔流动而移动。如果将个别板块过去的运动与地球上的一个固定来源(如所谓的“地幔热点”)进行比较，就可以确定它们的运动。这些热点是由地幔热柱产生的，地幔热柱是起源于核-地幔边界或附近的大规模物质热化学隆起。这些热物质的涌出会在地球表面产生火山活动，当板块在其上方移动时，火山活动保持相对静止，产生成分截然不同的火山链，它们离热点越远，火山链就越古老。这项工作通过追踪几个记载较少的火山链的年龄、成分和形态，试图更好地了解发生在中白垩世(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和中太平洋山脉。该团队将能够测试这些地物是否是由目前法属波利尼西亚北部地区下方的地幔热柱建造的。综合的年龄和化学结果将被用来限制大约100 Ma的重大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，海上探险将包括来自内华达大学拉斯维加斯分校和加州州立大学长滩分校少数族裔服务机构的8名本科生研究参与者。该项目包括一项为期31天的海上探险，以疏浚赫斯隆起和中太平洋山脉及其附近的海山、海脊和海隆。此外，该小组将分析在美国国家海洋和大气局海洋勘探和研究探险中从卡林岭发现的玄武岩，以及即将进行的E/V鹦鹉螺号前往利廖奥卡拉尼海山探险的样本。陆上工作将包括从具有代表性的熔岩流中获取40Ar/39Ar年龄测定和地球化学示踪剂(常量元素和微量元素；锶-钕-铅-氢同位素)。这些新的样本和全面的数据集将允许检验以下假设：h1)利留奥卡拉尼海山和赫斯隆起是由马克萨斯地幔羽流形成的。2)皮特凯恩地幔羽流是卡林岭和中太平洋山脉的主要来源。中太平洋山脉记录了白垩纪板块运动的时间和方向变化。(4)中太平洋山脉和海斯隆起的构造受羽流-(远)脊相互作用的控制，形成软流层熔融通道。验证这些假设将有助于更好地理解地幔热柱动力学，以及对海洋地貌和大型火成岩省建造的“自下而上”控制。此外，绘制地幔热柱的长期表达图，可以无与伦比地洞察为热点火山活动提供物质来源的地幔储集层。地质年代学、化学和形态学的结合将使白垩纪正常超时时期(122-83 Ma)的太平洋绝对板块运动模型得到显著改进。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.