Collaborative Research: Displacement history of the Pearya terrane, Ellesmere Island - evaluating a strike-slip origin for the Canadian Arctic margin

该项目是对构成埃尔斯米尔岛皮利亚地体的基底岩石进行的构造、岩石学和地质年代学研究，埃尔斯米尔岛构成了北美最北端的陆地。该构造地体与斯瓦尔巴群岛和格陵兰岛的陆壳具有地质相似性。据推测，皮亚地体是加拿大北极边缘被板块构造过程移位的地壳碎片的最好例子。一种关于皮亚地体起源的构造模型(古生代西北航道模型)假定，组成科迪勒拉西北部(如阿拉斯加)的许多外来或远距离旅行的地质地体起源于格陵兰和斯堪的纳维亚共同的加里东造山带，随后在大约4亿年前通过走滑断层向西移动到现在的位置。缺乏关于皮亚地体的时间和运动感的文献，严重限制了对北美北极边缘构造演化的理解，为最近的模型留下了空间，这些模型声称皮亚是静止的，不是构造置换的结果。该项目包括实地观察和从皮亚地体偏远的南部边界采集样品，将用于测试这些模型。该项目是由德国联邦地球科学和自然资源研究所组织的2017年环-北极结构事件考察的一部分，该研究所将为实地工作提供后勤支持。该项目将与来自五个国家的科学家进行国际合作。除了该项目的科学贡献外，这项研究还将有助于对研究生和本科生进行一项重要的科学、技术、工程和数学(STEM)学科的培训，这对增强美国劳动力的兼容性非常重要。该项目还将有助于扩大STEM中任职人数不足的群体。研究成果将通过讲座与公众分享，并将在同行评议的科学文献和专业学会会议上发表。了解北美北极边缘的地质演化对于了解与北极地区有关的重要科学、政治和经济问题至关重要。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。该项目的最终目标是为皮亚地体复杂的南部边界的演化建立一个地层、构造和变质框架。这项研究包括对皮亚地体南部边缘的结晶基底和主要断裂进行运动学、岩石年代学和Ar-Ar热年代学综合分析，并通过砂岩岩石学、碎屑锆石铀铅和Hf分析以及泥岩的主元素、痕量元素和钕同位素地球化学进行跨地体边界的详细地层对比。尽管加拿大北极边缘经常被引用为大规模地体转换的例子，但人们对可能容纳如此深刻位移的构造知之甚少。该项目将根据与扭压有关的构造来评估可能的走滑构造，这可能与早先观察到的直线收缩相一致。这项研究的结果将提供关于变质作用年龄和剪切带早期韧性历史的关键时间，以便洞察普遍存在的叠印。首席调查人员还将评估不同断块中的重叠组合的地层学，以确定它是一个单一的组合，还是实际上是空间上分离的沉积体系的时间相关性。通过产生与地质学相关的可靠数据集，该项目将有助于区分目前存在的关于皮利亚地体和北极更大构造发展的不同模型。

This project is a structural, petrologic and geochronologic study of basement rocks that comprise the Pearya terrane of Ellesmere Island, which forms the northernmost landmass of North America. This tectonic terrane has geologic affinities with continental crust in Svalbard and Greenland. It is postulated that the Pearya terrane is the best example along the Canadian Arctic margin of a crustal fragment that has been displaced by plate tectonic processes. A proposed tectonic model for the origin of the Pearya terrane (the Paleozoic Northwest Passage model) postulates that many exotic or far-travelled geologic terranes that make up the northwestern Cordillera (e.g. Alaska) originated in the Caledonian orogenic belt shared by Greenland and Scandinavia, and subsequently traveled westward on a strike-slip fault to their current location about 400 million years ago. The lack of documentation on the timing and movement sense of the Pearya terrane severely limits understanding of the tectonic evolution of the Arctic margin of North America, leaving room for recent models that claim Pearya was stationary and was not the result of tectonic displacement. This project includes field observations and sample collection from remote southern boundary of the Pearya terrane that will be used to test these models. The project is part of the 2017 Circum-Arctic Structural Events Expedition organized by the German Federal Institute for Geosciences and Natural Resources, who will provide logistical support for the fieldwork. The project will involve international collaboration with scientists from five countries. In addition to the scientific contributions of the project, the study will contribute to training of graduate and undergraduate students in an important science, technology, engineering and mathematics (STEM) discipline, which is important in contributing to the enhanced compatibility of the U.S. workforce. The project will also contribute to broadening of underrepresented groups in STEM. Research results will be shared with the public through lectures and will be published in the peer reviewed scientific literatures and presentations at professional society meetings. Understanding the geological evolution of the North American Arctic margin is critical to informing important scientific, political and economic issues associated with the Arctic region. This award is cofunded by the NSF Office of International Science and Engineering.The ultimate goal of this project is to establish a stratigraphic, structural and metamorphic framework for the evolution of the complex southern boundary of the Pearya terrane. The study entails integrated kinematic, petrochronologic and argon-argon thermochronologic analysis of the crystalline basement and major faults at the southern Pearya terrane margin; and detailed stratigraphic comparison across the terrane boundary through sandstone petrography, detrital zircon uranium-lead and hafnium analysis, and major, trace element and neodymium isotope geochemistry on mudstone. Although the Canadian Arctic margin is often cited as an example of large magnitude terrane translation, little is known about the structures that may have accommodated such profound displacement. The project will evaluate possible strike-slip tectonics in light of structures associated with transpression, which may reconcile the earlier observations of straight contraction. The results of this study will provide critical timing on the age of metamorphism and the early ductile history of the shear zones in order to see through the pervasive overprinting. The principal investigators will also evaluate the stratigraphy of the overlap assemblage in different fault blocks to determine whether it is a single assemblage or, in fact, time correlatives of spatially separate depositional systems. By producing a robust data set tied to the geology, this project will help discriminate among the disparate models that currently exist for the Pearya terrane and the larger tectonic development of the Arctic.