Collaborative Research: An Alaskan perspective on middle Paleozoic terrane translation, contraction, and subduction initiation in northwestern Laurentia

板块构造学的一个基本概念是，古代大陆边缘经历了一个从沉积物堆积的“被动”区向以俯冲、火山作用和造山作用为主的“活动”区转变的过程。发生这种转变的过程是通过沿着大陆边的俯冲开始。然而，现代的例子和俯冲开始的数值模型仍然存在很大的争议。晚古生代（Late Paleozoic）4.5亿~ 3亿年前）北美西北部从被动边缘到活动边缘的转变经常被引用为这一基本板块构造过程的经典例子，但对导致这一俯冲起始事件的北方阿拉斯加和加拿大育空地区关键事件的性质和时间知之甚少。这项研究促进了美国三个机构的学术研究人员与美国地质调查局（USGS）的政府研究人员之间的合作，以更好地了解北美偏远和未充分研究地区的晚古生代构造事件。一个多样化的本科生和研究生群体将参与每个机构的研究活动。此外，研究小组将与美国鱼类和野生动物管理局以及美国地质勘探局合作，向公众传播阿拉斯加北极的地质知识，以提高美国的经济竞争力，促进下一代北极地球科学家的培养。北美中古生代构造演化的最新模式（Laurentia）强调边缘平行运输的环北极的珊瑚礁，其次是广泛的大陆俯冲开始从育空地区到内华达州。然而，中古生代造山事件的时间，性质和持续时间仍然模糊不清。该项目将重点研究阿拉斯加北方北极阿拉斯加地区的关键构造关系和独特的泥盆纪-石炭纪同造山沉积岩和岩浆岩。该研究包括三个主要组成部分：1）与区域物源数据集的发展相结合的同造山岩石的检查; 2）区域中上泥盆统火成岩的岩石学，地球化学和地质年代学检查; 3）与区域地震数据集相结合的野外结构研究，以重建阿拉斯加北极地区泥盆纪-石炭纪变形的风格。这项工作将提供关键的新的见解，古生代构造演化的北美西北部和更大的环北极地区，以评估几个俯冲启动机制的可行性。此外，该项目将为北极中生代构造重建提供新的切入点，与地球科学的几个分支学科有关。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A fundamental concept in plate tectonics is that ancient continental margins undergo a conversion process from “passive” zones of sediment accumulation to “active” zones dominated by subduction, volcanism, and mountain building. The process by which this transition occurs is through subduction initiation along continental margins. However, modern examples and numerical models of subduction initiation remain highly contentious. The late Paleozoic (ca. 450–300 million years ago) conversion of northwestern North America from a passive to an active margin is often cited as a classic example of this fundamental plate tectonic process, but very little is known about the nature and timing of key events in northern Alaska and Yukon, Canada, that led to this subduction initiation event. This study promotes collaboration between academic researchers at three U.S. institutions and government researchers at the United States Geological Survey (USGS) to better inform our understanding of late Paleozoic tectonic events in a remote and understudied region of North America. A diverse group of undergraduate and graduate students will participate in research initiatives at each institution. In addition, the research team will collaborate with the United States Fish and Wildlife Service and the USGS to disseminate geologic knowledge of Arctic Alaska to the public, to enhance the economic competitiveness of the U.S. and facilitate the training of the next generation of Arctic Earth scientists.Recent models for the middle Paleozoic tectonic evolution of North America (Laurentia) highlight margin-parallel transport of circum-Arctic terranes followed by widespread continental subduction initiation from the Yukon to Nevada. However, the timing, nature, and duration of middle Paleozoic orogenic events remain ambiguous. This project will focus on key structural relationships and unique Devonian–Carboniferous synorogenic sedimentary and magmatic rocks within the Arctic Alaska terrane of northern Alaska. The research consists of three major components: 1) the examination of synorogenic rocks coupled with the development of a regional provenance dataset; 2) a petrological, geochemical, and geochronological examination of regional Middle to Upper Devonian igneous rocks; and 3) a field-based structural study integrated with regional seismic datasets to reconstruct the style of Devonian–Carboniferous deformation in Arctic Alaska. This work will provide critical new insights into the Paleozoic tectonic evolution of northwestern North America and the greater circum-Arctic region to assess the viability of several subduction initiation mechanisms. In addition, this project will provide new piercing points for Mesozoic tectonic reconstructions of the Arctic, with relevance to several subdisciplines of the geosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.