Collaborative research: Taking the pulse of the Northwest Hawaiian Ridge: Implications for Flux Variations and mid-Cenozoic Pacific Plate Motions

夏威夷群岛的演变以及大岛上的岩浆活动如何以及为什么会随着时间的推移而变化，对于从科学和实践的角度来理解这一点都很重要。夏威夷岛是一系列岛链(夏威夷-帝王链)的最新表现，该链与地幔中的单一上升流(即地幔热柱)有关，它周期性地冲出洋壳，将大量熔岩喷发到海底并建造岛屿。夏威夷-帝王链不仅是地幔热柱的经典例子，也是已知的最热的。这股羽流已经活跃了8000万年，形成了一条从夏威夷到太平洋西北部长约6000公里的火山轨迹。尽管这条链很重要，不仅对于我们了解地幔热柱的起源和演化，而且对于构造板块如何随着时间的推移穿过地球表面，我们在喷发的年龄进程和沿链喷发的熔岩的化学变化方面的知识仍然存在重大差距。这项研究分析了夏威夷-帝王链西北部11座火山的20个新收集的岩石样本。这项工作使用最先进的Ar-Ar测年技术提供了新的年龄数据，并收集了熔岩的全岩地球化学数据，以及一套放射性同位素的数据，以确定与喷发相关的地幔温度。这些数据将被用来更好地理解夏威夷地幔热柱的岩浆演化，以及它的年龄进程如何更好地约束太平洋盆地板块构造。这项工作的更广泛影响包括对学生进行培训，并为生物学家提供更好的信息，了解大洋彼岸夏威夷土著物种的生物地理和辐射。研究工作的成果将用于与博物馆工作人员合作，为火奴鲁鲁主教博物馆制作关于夏威夷群岛和夏威夷皇帝链的新互动展览。这为科学提供了一个重要的公共宣传工具，因为主教博物馆每年吸引着数十万来自美国和海外的游客。夏威夷-帝王链是地球上定义最明确的地幔热柱，最适合于评估与地幔热柱相关的过程，以及评估它们与板块构造和构造板块运动的关系。这项研究使用了20个新收集的样本，这些样本是在一次海洋探险中收集的，这些样本是在一次海洋考察中收集的，这些样本描述了夏威夷-帝王链的西北部地区，使用的是新的美国夏威夷海洋纪念碑中的遥控飞行器。有关这些样品的地球化学和矿物学关系的信息将利用各种观测和分析技术产生。除了对样品进行岩石学和矿物学检查外，还将收集全岩地球化学数据，以及铅、锶、钕和氦等放射性同位素的组成和比例的质谱学数据。橄榄石的成分也将被确定。这项研究将按照共同标准汇编和更正该岛链西北部的所有已公布数据，并将其与新数据结合起来，创建一个全面的地球化学和年龄数据库，可用于测试该部分岛链在新生代期间的形成和演化模型。将使用地球化学和地球物理方法对结果进行模拟，以提供对地幔热柱和板块运动学的基本新见解。新的地球化学数据将被用来确定夏威夷地幔热柱来源成分的长期演化，并评估地幔温度、熔融压力和/或来源岩性是否随着时间的推移发生了系统的变化。新的年龄将被用来修正新生代太平洋板块运动，并计算微分运动，作为岛链上应力变化的替代，并有时间评估板块运动对岩浆通量速率的影响。这一裁决反映了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。

The evolution of the Hawaiian Islands and how and why magmatism on the Big Island changes over time is important to understand both from a scientific and practical point of view. The island of Hawaii is the most recent expression of a chain of islands (the Hawaiian-Emperor Chain) related to a single upwelling in the mantle (i.e. a mantle plume) that periodically punches up through the ocean crust and erupts massive amounts of lava onto the seafloor and builds islands. The Hawaiian-Emperor Chain is not only the classic example of a mantle plume, it is also the hottest known. This plume has been active for 80 million years and has formed a trail of volcanoes extending ~6000 km in length from Hawaii to the northwestern reaches of the Pacific Ocean. Despite the importance of this chain, not only to our understanding of the origin and evolution of mantle plumes but also to how tectonic plates move across the face of the Earth over time, there are still major gaps in our knowledge of the age progression of the eruptions and chemical variations of the erupted lavas along the chain. This research analyzes twenty newly-collected rock samples from eleven volcanoes along the northwestern part of the Hawaiian-Emperor Chain. This work provides new age dates using state-of-the-art argon-argon dating techniques and collects whole-rock geochemistry on the lavas, as well as data on a suite of radiogenic isotopes to determine mantle temperatures associated with the eruptions. These data will be used to better understand the magmatic evolution of the Hawaiian mantle plume and how its age progression better constrains Pacific Ocean basin plate tectonics. Broader impacts of the work include student training and providing biologists with better information about the biogeography and radiation of native Hawaiian species across the ocean. Results of the research work will be used to create a new interactive exhibit on the Hawaiian Islands and the Hawaiian-Emperor Chain for the Bishop Museum in Honoloulu, in collaboration with museum staff. This provides a major public outreach vehicle for science as the Bishop Museum attracts hundreds of thousands of visitors a year from the US and abroad. The Hawaiian-Emperor Chain is the most well-defined mantle plume on the planet and is optimal for evaluating mantle plume related processes and assessing their relationship to plate tectonics and tectonic plate motion. This research uses 20 newly collected samples from eleven volcanoes that were collected on an oceanographic expedition characterizing the northwest region of the Hawaiian-Emperor Chain using remotely operated vehicles in the new US Hawaiian Marine Monument. Information on the geochemistry and mineralogical relationships of these samples will be generated using a wide variety of observational and analytical techniques. In addition to petrographic and mineralogical examination of the samples, whole rock geochemical data will be collected, as will mass spectrometric data on the composition and ratios of the radiogenic isotopes: lead, strontium, neodymium, and hafnium. Olivine compositions will also be determined. The research will compile and correct, to common standards, all published data from the northwest part of this island chain and combine it with the new data to create a comprehensive geochemical and age date database that can be used to test models for this part of the chain's formation and evolution during the Cenozoic. Results will be modeled using geochemical and geophysical approaches to provide fundamental new insights into mantle plumes and plate kinematics. New geochemical data will be used to determine the long-term evolution of the Hawaiian mantle plume source components and to evaluate whether there have been systematic variations in mantle temperature, melting pressure, and/or source lithology over time. The new ages will be utilized to revise Cenozoic Pacific plate motions and to compute differential motions as proxies for stress changes along the island chain with time to evaluate the effects of plate motion on magma flux rate.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.