RUI: Magmatic Evolution Leading Up to the Modern Aleutian Arc on the Alaska Peninsula

Allegheny College, Meadville PA

Investigators

Abstract

Alaska contains the largest number of active volcanoes in the United States and is one of the most volcanically active regions in the world. Most of the volcanoes in Alaska form a belt that includes the Aleutian Islands and extends landward onto the Alaska Peninsula, ending across the Cook Inlet from Anchorage. The Alaska Peninsula hosts more than 20 volcanoes with historic activity, five with major eruptions in the past 25 years, and includes the world's largest eruption of the 20th century. This project will investigate the growth of the volcanic system on the Alaska Peninsula and evaluate the factors that influence the composition and behavior of volcanoes in this region. The results of this project will contribute to ongoing work of the U.S. Geological Survey and Alaska Volcano Observatory for understanding volcanic behavior in a region where there are roughly 30,000 people per day transported in commercial aircraft over the volcanoes and where eruptions can have severe impact on Anchorage (Alaska's largest population center) and along the Kenai Peninsula. The Alaska Peninsula is also one of the nation's most important mineral resource regions; this project will provide an improved regional framework that will be useful for future detailed studies to delineate economic mineral deposits. Scientific advances made through this project will also contribute to the public-outreach mission of Lake Clark and Katmai National Parks, where several of the volcanoes of this study are located. This project will additionally provide high-level STEM training for undergraduate students. The project is highly cost-effective because it uses publically-available sample collections of the U.S. Geological Survey, building on past investments in federal funding. Southern Alaska is one of the best places in the world to investigate long-term magmatism and crustal growth along a convergent margin, as recognized by the GeoPRISMS community who selected the Alaska/Aleutian subduction zone as the highest priority site for the Subduction Cycles and Deformation (SCD) initiative. This two-year project will benefit the GeoPRISMS community with an unprecedented synoptic study to evaluate temporal and along-strike geochemical trends for Eocene through Quaternary igneous rocks on the Alaska Peninsula. Data will include major and trace element, whole rock Nd-Sr-Hf and zircon Hf-isotopes, and 40Ar/39Ar and zircon U/Pb dating on volcanic and plutonic rocks. The results of this research will provide new constraints on the continental portion of Aleutian arc including: i) along-arc trends in magma chemistry and relationships with sediment flux and regional tectonics, ii) geochemical products of subduction over time and how these influence the composition of new continental crust, and iii) the timing of subduction initiation and relationship to Pacific-wide versus local tectonic processes. This work is in concert with the GeoPRISMS SCD initiatives to "focus on long-term margin evolution and material transfer" and "the growth and evolution of volcanic arcs and continents" and can be integrated with other projects (i.e., geophysical studies of the southern Alaska margin) to yield advances in understanding the regional controls on convergent margin magmatism.