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

板块构造学中的一个基本概念是，古代大陆边缘经历了一个从沉积堆积的“被动”带到以俯冲、火山作用和造山为主的“主动”带的转换过程。这一转变发生的过程是通过大陆边缘的俯冲启动。然而，现代俯冲启动的例子和数值模型仍然存在很大的争议。北美西北部晚古生代(约4.5亿-3亿年前)从被动边缘到活动边缘的转换经常被认为是这一基本板块构造过程的经典例子，但人们对导致这次俯冲启动事件的阿拉斯加北部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和美国地质调查局(USGS)的政府研究人员之间的合作，以更好地了解北美一个偏远和未被研究的地区的晚古生代构造事件。一群不同的本科生和研究生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植物管理局和美国地质调查局合作，向公众传播北极阿拉斯加的地质知识，以提高美国的经济竞争力，并促进对下一代北极地球科学家的培训。最近的北美中古生代构造演化模型(劳伦蒂斯)强调，从育空到内华达州的大范围大陆俯冲引发了环北极地体的边缘平行运输。然而，中古生代造山事件的时间、性质和持续时间仍然不清楚。该项目将重点研究阿拉斯加北部北极阿拉斯加地体内的关键构造关系和独特的泥盆纪-石炭纪同造山沉积和岩浆岩。这项研究包括三个主要部分：1)同造山岩的研究和区域物源数据库的建立；2)区域中、上泥盆统火成岩的岩石学、地球化学和年代学研究；3)结合区域地震数据的野外构造研究，以重建阿拉斯加北部泥盆纪-石炭纪的变形样式。这项工作将对北美西北部和大环北极地区的古生代构造演化提供关键的新见解，以评估几种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相关。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.