Collaborative Research: Using the Rurutu Hotspot to Evaluate Mantle Motion and Absolute Plate Motion Models

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Linear tracks of submarine volcanoes (i.e., the Hawaiian-Emperor and Louisville volcanic chains) define the trace of the two longest-lived Pacific hotspots. These two hotspot tracks have long been used to model tectonic plate motion and define how the continents have moved over the face of the globe over time. It has generally been believed that hotspots, which originate deep in the mantle, are fixed and that, as the plate moves over it, the hot spot punches through the crust resulting in a linear chain of volcanoes that can be used to show the speed and direction of plate motion over 10's of millions of years. Mounting evidence now, however, indicates that hotspots may not actually be fixed with respect to the mantle or each other. To test the hypothesis of a moving hotspot reference frame, this research will define a third, long-lived, Pacific hotspot track, the Rurutu hotspot, and compare it with the Hawaiian-Emperor and Louisville chains. Twenty submarine volcanoes near the Samoa Islands in the western Pacific Ocean will be sampled and geochemical analyses of the lavas will be collected. Argon, produced from radioactive decay, will be used to determine the ages of the volcanoes. The chemisty of the lavas, especially the elemental abundances and the Sr, Ne, Pb, and Hf isotopes signatures, will be used to (1) distinguish Rurutu volcanoes from unrelated ones and (2) determine the geochemical fingerprint and evolution of the hotspot. Samples dredged from the seafloor will be described and analyzed on the ship by Laser Induced Breakdown Spectroscopy. Mapping and marine geophysical data will be collected and used to guide potential dredging targets. Broader impacts include a strong and large student training component in which three graduate students and 10 undergraduates will go to sea and be intimately involved in the project. This will help build a more diverse scientific workforce by recruiting students from a Hispanic Serving Institution in Texas and training them in state-of-the-art geochemical analysis and data interpretation. This research will foster inter-institutional collaboration between three institutions and will support two early career investigators.