Collaborative Research: High Precision 40Ar/39Ar Geochronology and Paleomagnetism to Determine the History and Consequences of Louisville Mantle Plume Motion

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A major outstanding question in geodynamics is whether primary hotspots in the Pacific, like the Hawaiian and Louisville hotspots, experienced similar amounts of plume motion or whether they moved independently. In December 2010 IODP Expedition 330 to the Louisville seamount trail set out to answer this critical question. Preliminary shipboard paleomagnetic data (although based upon limited shipboard sampling) clearly show the Louisville hotspot did not experience the same large 15° shift in paleolatitude as recorded for the Hawaiian hotspot between 80 and 50 Ma. Critically, these shipboard data neither allow for estimates of the duration of volcanism at individual sites drilled nor for the inclination of many cooling units (about half have no data yet or only a single sample). As importantly, the abundance of (mostly submarine) volcaniclastic material recovered makes estimating the paleolatitudes less straightforward than for the sites on the Hawaii-Emperor trail, where a sequence of discrete (primarilythat might be expected to have random directions, instead have consistent inclinations that are similar to those of intercalated lava flows and therefore may provide valuable paleolatitude information. The proponents therefore propose additional 40 Ar/39 Ar age determinations, paleomagnetic and rock magnetic studies, and integration of additional shore-based and shipboard data (e.g. borehole magnetic anomalies) that will allow the to address the following questions: 1. How long did it take to build the volcanic sequences drilled during Expedition 330 and are these intervals (and associated quiescence periods) long enough to average out secular variation?2. Do Louisville seamounts have post-erosional volcanism and if so what is its duration?3. What is the origin of consistent inclinations in some volcaniclastic units and do these provide a time-averaged remanence that can improve paleolatitude estimates?4. Are the inclination data from the Louisville seamounts sufficiently similar to provide a robust paleolatitude from pooled data?5. Can we use the ages and paleolatitude history of the Louisville hotspot to improve absolute plate motion models for Pacific plate? The results of this study will allow the proponents to (1) provide the most accurate and precise age framework for volcanic activity along the Louisville seamount trail, (2) to significantly reduce on the uncertainties in paleolatitude estimates, and (3) help to improve absolute plate motion model for the Pacific Plate taking into account the (lack of) motion of the individual Hawaiian and Louisville hotspots.Broader Impact and Educational Outreach: The proposed project is part of an international collaborative effort in support of the science objectives of IODP Expedition 330 to the Louisville Seamount Trail. The proponents are collaborating with eight international researchers from Japan, UK and Australia, with whom they will generate as complete as possible and much needed high-precision 40 Ar/39 Ar and paleomagnetic data sets. The Proponents will coordinate this concerted effort over the two years of our project, with the ultimate goal to delineate the most accurate paleolatitude and age history for the Louisville hotspot. They also will organize a series of outreach activities, including expanding the Expedition 330 website started by Koppers by adding scientific products and data sets resulting from this project and by linking these in with the online Seamount Catalog and MagIC. This work will be part of the Ph.D.thesis of two students at OSU and SIO.