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

阿拉斯加/阿留申弧区是北美地质活动最活跃的地区，有大量的大地震和50多座活火山喷发。准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-北太平洋地区的起源以及几个环太平洋火山带如何相互联系的关键因素之一。我们对阿留申弧火山活动如何开始的理解很大程度上是由于缺乏关于阿留申群岛最早的火山岩年龄的数据。拟议的阿留申弧形初始调查包括采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形火山活动开始的时间，并突出与太平洋其他地区火山活动的开始以及5200万年前大洋板块相对运动的快速变化之间的潜在联系。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太平洋沿岸的居民造成重大火山和地震危害的基本信息。拟议的研究将采用最先进的40Ar/39Ar和U-Pb年代学，以及对年代岩石的地球化学和同位素分析。重点放在阿马蒂尼亚克、乌拉克和基斯卡群岛的水下露头上，这些岛屿拥有探索阿留申群岛早期历史的最大潜力。新的地质年代学和地球化学数据将精确地限制阿留申弧形开始的时间，喷发产物的成分，以及它们是如何在弧形最早的历史中演变的。这些信息还将用于评估现有的阿留申弧初和太平洋板块在始新世中期运动的构造模型。该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大学费尔班克斯分校/USGS的科学家之间建立一种新的合作，这可能会使GeoPRISMS计划在其持续时间内受益。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检查阿留申弧形及其弧前结构的努力应集中在哪里，以最好地解决俯冲带启动的问题。

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.