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

该项目的主要目的是了解残余石榴石和流体在控制阿留申岛弧不同部分产生的原始镁安山岩岩浆中U系列不平衡状态方面的竞争作用。本研究的研究对象包括以下阿留申火山：科罗文火山、小西特金火山和皮普火山。每一座火山的熔岩都在沿弧线的不同位置沿着不同的地球化学趋势演化，那里的垂直俯冲速率和推断的俯冲系统的热状态不同。在这种情况下，皮普火山特别令人感兴趣，因为它是遥远西部阿留申科曼多尔斯基地区相对著名的镁质安山岩。主要的分析工作是测量234U/238U、230Th/232Th和238U、232Th和226Ra的浓度。此外，还将收集所有尚不存在这些数据的样品的全岩常量元素和微量元素数据以及铅、锶、钕和氢的同位素组成。一些样品的制备，包括铅、锶、钕和氢的柱化学，将在南卡罗来纳大学进行，但所有的U系列化学和所有的同位素测量(除了氢)将在伍兹霍尔海洋研究所的实验室进行。这个项目将作为南卡罗来纳大学研究生克里斯·怀亚特攻读博士学位的主要基础，他将在两位PI的指导下工作。该项目还将资助本科生的参与，其中将包括为学业优秀和上进心强的学生进行本科生研究。

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.