Collaborative Research: Do improved absolute plate motion models based on Cretaceous Western Pacific seamounts relate Louisville to Ontong-Java?

地球上的海洋包含大量的火山结构，其中许多仍未被勘探和/或解释。这些构造中的一些形成了逐渐古老的火山链，被称为海山踪迹，最初被认为是地球构造板块移动到地幔中固定的“热”点上的结果，产生的熔融随着时间的推移依次形成火山。在普遍接受的对这种火山活动的解释中，上升的地幔热柱提供了物质和热量，产生了建造火山的熔体。在对这种动力学进行建模时，羽状“头部”的最初到达会产生异常大量的熔融，以一个大的火成岩省为代表，而羽状尾部则会产生一个随时间推移的火山链，记录了自热点最初喷发以来构造板块的运动。这一认识导致了对地球板块运动的基本定义。然而，在面积最大的火成岩大省--西太平洋的安通-爪哇高原--的情况下，一条应该由羽状尾巴形成的火山海山踪迹尚未得到证实。路易斯维尔热点已经被认为是一个可能的候选热点，它出现在安通-爪哇高原并产生路易斯维尔海山链，然而目前的板块运动模型表明，两者之间存在不匹配。仔细观察自安通-爪哇高原时代(~120 Ma)以来太平洋板块板块运动模型的构建方式，就会发现一些火山构造和所用的假设引入了足够的不确定性，值得重新评估70 Ma之前的板块运动模型。可供选择的板块运动模型可能允许路易斯维尔和安通-爪哇高原的关系。这一模型是可以通过研究另一个热点轨迹来检验的--火山活动的连续记录可以追溯到120 Ma--这是最近被发现的。研究结果对认识板块构造运动以及大火成岩省与热点轨迹的关系具有重要意义。该项目将为未来的科学家提供重要的培训内容：该项目将包括一次海上岩石采样探险，将为来自3个学生人数严重不足的机构的7名本科生、2名研究生、1名博士后研究员和3名早期职业科学家提供海上经验。考察后分析工作将确定研究生高级学位工作的重要部分，以及一名博士后研究人员工作的重要部分。这项研究的主要目的是提高我们对(绝对)板块运动以及羽流热点轨迹的关系和演化的理解。在目前的绝对板块运动模型中，70 Ma之前的时间段严重依赖于与长期热点轨迹没有明显联系的非典型火山构造，包括：1)中太平洋山脉、莱恩群岛；2)沙茨基、赫斯隆起、音乐家海山、温特沃斯海山；以及3)尾流海山、马绍尔群岛、麦哲伦海山。重新评估来自中太平洋和西太平洋的新的和现有的数据表明，只有最后一组可能忠实地代表了绝对的板块运动。一个初步的(基于稀疏的现有数据)绝对板块运动模型表明，这些海山可能与目前的南太平洋热点萨摩亚和鲁鲁图(阿拉戈)有关。在这个项目中，我们将检验这样的假设：1)韦克-马歇尔-麦哲伦与萨摩亚和鲁鲁图(阿拉戈)热点有关；2)从新数据得出的板块运动模型将路易斯维尔与安通-爪哇高原联系起来。这些假设将通过为期37天的疏浚探险对维克-马歇尔-麦哲伦海山进行采样来验证。将分析岩石样品的主要、微量元素和同位素组成，并确定其年龄，以便正确追踪萨摩亚和鲁鲁图(阿拉戈)热点进入西太平洋。由此产生的热点轨迹将用于构建新的(绝对)板块运动模型，特别是在70 Ma之前的时期，该模型将用于评估路易斯维尔和安通-爪哇高原之间的潜在联系。该奖项反映了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。

Earth’s oceans contain a significant number of volcanic structures, many of which remain unexplored and/or unexplained. Some of these structures form chains of progressively older volcanoes, known as seamount trails, which were originally thought to result from Earth’s tectonic plates moving over a fixed “hot” spot in the mantle, producing melt that builds the volcanoes in sequence over time. In the commonly accepted explanation for this volcanic activity, a rising mantle plume delivers material and heat that produce the melt that constructs the volcanoes. In modeling such dynamics, the initial arrival of the plume “head” generates an unusually large amount of melt represented by a large igneous province, while the plume tail generates an age-progressive chain of volcanoes that record the motion of the tectonic plate since the initial eruption of the hotspot. This understanding has led to the fundamental definition of the motions of Earth’s plates. However, in the case of the most voluminous large igneous province - the Ontong-Java Plateau in the western Pacific - a volcanic seamount trail that should be created by a plume tail has not yet been confirmed. The Louisville hotspot has been proposed as a possible candidate hotspot emerging from the Ontong-Java Plateau and generating the Louisville seamount chain, however current models for plate motion suggest a mismatch between the two. A close look at the way plate motion models for the Pacific Plate have been constructed back to the age of the Ontong-Java Plateau (~120 Ma) suggests that some of the volcanic structures, and assumptions used, introduce sufficient uncertainty to merit a reassessment of plate motion models prior to 70 Ma. Alternative plate motion models may allow for a Louisville and Ontong-Java Plateau relationship. This model is testable by studying an alternative hotspot track—with a continuous record of volcanism extending back to 120 Ma—that has recently been recognized. Results have significant implications for understanding tectonic plate motion, as well as the relationship between large igneous provinces and hotspot tracks. This project will have a significant training component for future scientists: the project will include an at-sea rock sampling expedition that will provide seagoing experience to 7 undergraduates from 3 institutions with significant under-represented student populations, 2 graduate students, 1 postdoctoral investigator, and 3 early career scientists. Post-expedition analytical work will define a significant part of the graduate students’ advanced degree work and an important part of the work of one postdoctoral investigator. The primary objective of this study is to improve our understanding of (absolute) plate motion and the relation to and evolution of plume-derived hotspot tracks. In current absolute plate motion models, the time period prior to 70 Ma heavily relies on atypical volcanic structures that do not clearly relate to long-lived hotspot tracks, including: 1) Mid-Pacific Mountains, Line Islands; 2) Shatsky, Hess Rise, Musician Seamounts, Wentworth Seamounts; and 3) Wake Seamounts, Marshall Islands, Magellan Seamounts. Reassessing new and existing data from the Mid- and West-Pacific suggests only the last of these groups may faithfully represent absolute plate motion. A preliminary (based on sparse existing data) absolute plate motion model suggests that these seamounts could be related to the current South Pacific hotspots of Samoa and Rurutu (Arago). In this project, we will test the hypotheses that 1) Wake-Marshall-Magellan relate to Samoa and Rurutu (Arago) hotspots, and that 2) the plate motion model that can be derived from the new data relates Louisville with the Ontong-Java Plateau. These hypotheses will be tested by sampling the Wake-Marshall-Magellan seamounts with a 37-day dredging expedition. Rock samples will be analyzed for their major, trace element and isotopic compositions, and their ages will be determined, in order to properly trace the Samoa and Rurutu (Arago) hotspots into the West Pacific. The resulting hotspot tracks will be used to construct a new (absolute) plate motion model, particularly for the period prior to 70 Ma, and this model will be used to evaluate the potential connection between Louisville and the Ontong-Java Plateau.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.