MARGINS: Collaborative Research: A 21st Century Reconnaissance of Aleutian Arc Inception

阿拉斯加/阿留申弧是北美地质活动最活跃的地区，大地震频发，50多座活火山喷发。精确地确定阿留申弧是如何以及何时开始形成的，是了解白令海-阿拉斯加-北太平洋地区起源的关键因素之一，也是了解几个环太平洋火山带如何相互联系的关键因素之一。我们对阿留申岛弧的火山活动是如何开始的理解是模糊的，这在很大程度上是由于缺乏有关阿留申群岛最早火山岩年龄的数据。拟议的阿留申弧初始侦察调查包括取样和确定最古老的火山活动记录的年龄。其目的是确定阿留申弧火山活动何时开始，并强调与太平洋其他地方火山活动开始的潜在联系，以及5200万年前发生的海洋板块相对运动的快速变化。此外，拟议的研究将产生关于阿留申弧如何以及为什么对阿拉斯加和环太平洋地区的人口构成重大火山和地震危险的基本信息。拟议的研究将采用最先进的40Ar/39Ar和U-Pb地质年代学，以及地球化学和同位素分析的年代岩石。重点是阿马提尼亚克岛、乌拉克岛和基斯卡岛上的地面裸露物，这些地方最有可能探索阿留申群岛的早期历史。新的地质年代学和地球化学数据将精确地限制阿留申弧何时开始，喷发产物的成分是什么，以及它们在弧的早期历史中是如何演变的。这些信息也将用于评估中始新世阿留申弧起始和太平洋板块运动的现有构造模型。这个项目将在威斯康星大学麦迪逊分校、康奈尔大学和阿拉斯加费尔班克斯大学/美国地质勘探局的科学家之间建立一个新的合作关系，这可能会使地质系统项目在其持续期间受益。我们的发现将立即用于确定未来通过潜水rov、疏浚和地球物理成像来检查阿留申弧及其弧前结构的工作，以最好地解决俯冲带起始的问题。

The Alaska/Aleutian Arc is the most geologically active region in North America with abundant large earthquakes and eruptions from more than 50 active volcanoes. Determining precisely how and when the Aleutian Arc began to form is one of the key elements for understanding the origin of the Bering Sea-Alaska-North Pacific region as well as how several circum-Pacific volcanic zones are related to one another. Our understanding of how volcanism initiated in the Aleutian Arc is clouded due in large part to the scarcity of data that bear on the ages of the earliest volcanic rocks in the Aleutian Islands. The proposed reconnaissance investigation of Aleutian Arc inception involves sampling and determining the ages of the oldest records of volcanism. The aim is to define when Aleutian arc volcanism started and highlight potential linkages with the initiation of volcanism elsewhere in the Pacific and the rapid change in the relative motions of oceanic plates that occurred 52 million years ago. In addition, the proposed research will generate basic information regarding how and why the Aleutian arc poses significant volcanic and earthquake hazards to the population in Alaska and around the Pacific Rim.The proposed research will employ state-of-the-art 40Ar/39Ar and U-Pb geochronology, along with geochemical, and isotopic analysis of the dated rocks. The focus is on subaerial outcrops on Amatignak, Ulak, and Kiska islands, which hold the greatest potential for exploration into the early history of the Aleutians. New geochronologic and geochemical data will precisely constrain when the Aleutian arc inception began, what the compositions of the eruptive products were, and how they evolved through the earliest history of the arc. This information will also be used to evaluate the existing tectonic models of Aleutian arc inception and Pacific Plate motion during the middle Eocene. This project will forge a new collaboration between scientists at UW-Madison, Cornell University, and the University of Alaska-Fairbanks/USGS that may benefit the GeoPRISMS program for its duration. Our findings will be used immediately to determine where future efforts to examine the Aleutian Arc and its fore-arc structures via submersible ROVs, dredging, and geophysical imaging should concentrate to best address questions of subduction zone initiation.