Collaborative Research: Building an International Partnership for GeoPRISMS Research in the Aleutian-Primary Site through US Participation in Cruises of the German R/V Sonne

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Subduction of one tectonic plate beneath another is a fundamental geologic process, which has many important potential human impacts, including earthquakes and volcanic eruptions. Subduction also plays a key role in shaping Earth's surface, and has been particularly important in the formation of continents. This project will allow a group of U.S. scientists from the University of South Carolina and the University of Wisconsin to participate in two research cruises of the German Research Vessel Sonne. The expedition of the Research Vessel Sonne will collect rock samples from the seafloor in the Alaska-Aleutian subduction system and adjacent Bering Sea region in June-July 2016. This area has many earthquakes and volcanic eruptions, but little is known about its early geologic history and evolution. Samples collected during these scientific cruises will be used to understand the evolution of the Aleutian Island arc and adjacent Bering Sea region over the past 50 million years. Graduate and undergraduate students will participate on the cruises and gain important sea-going experience. All post-cruise data will be made available to the public.This project focuses on three scientific themes: (1) inception and early development of the Aleutian Island arc, (2) occurrence and composition of active volcanism in the western Aleutian arc, and (3) arc inputs - the age and composition of North Pacific Oceanic lithosphere. Dredging and subsequent geochemical and geochronologic studies will target submarine canyons and other exposed basement structures in the Aleutian forearc. Samples from these features will provide constraints on the timing and kinematics of Aleutian arc formation. Dredging will also target volcanic cones of the western Aleutian seafloor and fracture zones on the down-going north Pacific Plate. Samples from these features will be used to characterize inputs from subducted oceanic crust in the Aleutian arc and their relationship to regional patterns in along-strike geochemistry. These samples will also be used to provide improved understanding of the highly calc-alkaline western Aleutian seafloor volcanic rocks and their significance from the standpoint of geochemical source components for all Aleutian-Alaska volcanism, and for the source of arc volcanism globally.