Collaborative Research: Evaluating the Competing Roles of Garnet and Fluid in Controlling U-Th Disequilibria in Lavas of the Aleutian Island Arc

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The main objective of this project is to understand the competing roles of residual garnet and fluid in controlling the state of U-series disequilibria in primitive magnesian andesite magmas produced in different parts of the Aleutian island arc. The research target for this study includes the following Aleutian volcanoes: Korovin, Little Sitkin and Piip. Lavas from each of these volcanoes have evolved along distinctive geochemical trends at different locations along the arc where orthogonal subduction rates and the inferred thermal state of the subduction system are different. In this context Piip Volcano is of particular interest because it is a relatively well-known magnesian andesite occurrence in the far western Aleutian Komandorsky area. The main analytical effort will be the measurement of 234U/238U, 230Th/232Th and 238U, 232Th and 226Ra concentrations. In addition, whole rock major and trace element data and Pb, Sr, Nd and Hf isotopic compositions will be collected for all samples where such data do not already exist. Some sample preparation, including column chemistry for Pb, Sr, Nd and Hf, will be done at the University of South Carolina, but all U-series chemistry and all isotopic measurements (except Hf) will be made in the laboratories at the Woods Hole Oceanographic Institution. This project will serve as the primary basis for the PhD degree of University of South Carolina graduate student Chris Wyatt, who will work under the direction of both PI's. The project also funds undergraduate participation, which will include undergraduate research for academically strong and well-motivated students.