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，其中许多仍然未被探索和/或无法解释。这些结构中的一些形成了逐渐老化的火山链，被称为海山小径，最初被认为是由于地球的构造板块在地幔中的一个固定的“热点”上移动，随着时间的推移，产生了熔化，从而建立了火山。对于这种火山活动，普遍接受的解释是，上升的地幔柱提供了物质和热量，产生了构造火山的熔体。在模拟这样的动力学，最初到达的羽“头”产生了异常大量的熔融代表了一个大的火成岩省，而羽尾产生了一个年龄渐进的火山链，记录了运动的构造板块，因为最初的热点喷发。这种认识导致了地球板块运动的基本定义。然而，在最大的大型火成岩省-西太平洋的Ontong-Java高原-一条应该由羽流尾造成的火山海山痕迹尚未得到证实。路易斯维尔热点已被提议作为一个可能的候选热点出现在Ontong-Java高原，并产生路易斯维尔海山链，但目前的板块运动模型表明两者之间的不匹配。仔细研究太平洋板块运动模型的构建方式，可以追溯到Ontong-Java高原（~120 Ma）的年龄，这表明一些火山结构和使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。其他板块运动模型可能允许路易斯维尔和Ontong-Java高原的关系。这个模型是可测试的，通过研究一个替代热点跟踪火山活动的连续记录可追溯到120马，最近已被确认。研究结果对于理解构造板块运动，以及大火成岩省和热点轨迹之间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：该项目将包括一次海上岩石取样考察，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名博士后调查员和3名早期职业科学家提供海上经验。考察后的分析工作将确定研究生的高级学位工作的重要组成部分，一个博士后研究员的工作的重要组成部分。 这项研究的主要目的是提高我们的理解（绝对）板块运动和羽衍生热点轨迹的关系和演变。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非典型的火山结构，这些火山结构与长期存在的热点轨迹没有明显的关系，包括：1）中太平洋山脉，莱恩群岛; 2）沙茨基，赫斯海隆，音乐家海山，温特沃斯海山; 3）威克海山，马歇尔群岛，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，只有最后一组才能忠实地代表绝对的板块运动。一个初步的（根据稀少的现有数据）绝对板块运动模型表明，这些海山可能与萨摩亚和鲁鲁图（阿拉戈）目前的南太平洋热点有关。在这个项目中，我们将测试的假设，1）唤醒马歇尔麦哲伦与萨摩亚和鲁鲁图（阿拉戈）热点，2）板块运动模型，可以从新的数据相关路易斯维尔与翁通爪哇高原。这些假设将通过为期37天的疏浚考察对Wake-Marshall-Magellan海山进行取样来检验。将分析岩石样本的主要成分、微量元素和同位素组成，并确定其年龄，以便适当追踪萨摩亚和鲁鲁图（阿拉戈）热点进入西太平洋。由此产生的热点轨道将被用来构建一个新的（绝对）板块运动模型，特别是在70 Ma之前的时期，这个模型将被用来评估路易斯维尔和Ontong-Java Plateau之间的潜在连接。这个奖项反映了NSF的法定使命，并已被认为是值得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的支持。

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.