Collaborative Research: Taking the Pulse of the Northwest Hawaiian Ridge: Implications for Flux Variations and Mid-Cenozoic Pacific Plate Motions

点击翻译按钮获取中文摘要

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.