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（Ellesmere Island）梨梨亚地体（Pearya terran）基底岩石的构造、岩石学和地质年代学研究，该地体构成了北美最北端的大陆。该构造地体与斯瓦尔巴群岛和格陵兰岛的大陆地壳具有地质相似性。据推测，梨亚地体是沿加拿大北极边缘由板块构造过程移位的地壳碎片的最好例子。一种关于梨亚地体起源的构造模型（古生代西北通道模型）假设，构成科迪勒拉西北部的许多外来的或远行的地质地体（例如阿拉斯加）起源于格陵兰和斯堪的纳维亚共有的加里东造山带，随后在大约4亿年前通过走滑断层向西移动到它们现在的位置。由于缺乏关于梨亚地体的时间和运动意义的文献，严重限制了人们对北美北极边缘构造演化的理解，从而为最近的模型留下了空间，这些模型声称梨亚地体是静止的，不是构造位移的结果。该项目包括实地观察和从遥远的梨亚地层南部边界采集样本，这些样本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，该研究所将为实地考察提供后勤支持。该项目将涉及来自五个国家的科学家的国际合作。除了该项目的科学贡献外，该研究还将有助于培养重要的科学、技术、工程和数学（STEM）学科的研究生和本科生，这对提高美国劳动力的兼容性非常重要。该项目还将有助于扩大STEM中代表性不足的群体。研究成果将通过讲座与公众分享，并将在同行评审的科学文献中发表，并在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相关的重要科学、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梨梨亚地体复杂的南边界的演化建立一个地层、构造和变质格架。该研究对梨梨亚地体南部边缘的结晶基底和主要断裂进行了运动学、岩石年代学和氩-氩热年代学综合分析；并通过砂岩岩石学、碎屑锆石铀铅铪分析、泥岩主微量元素和钕同位素地球化学等方法进行了跨地界的详细地层对比。虽然加拿大的北极边缘经常被引用为一个大震级地形平移的例子，但人们对可能容纳如此深刻位移的结构知之甚少。该项目将根据与逆压有关的构造评估可能的走滑构造，这可能与早期的直线收缩观测相一致。这项研究的结果将提供变质作用的年龄和剪切带的早期韧性历史的关键时间，以便看穿普遍的套印。主要研究人员还将评估不同断块中重叠组合的地层学，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。通过生成与地质相关的可靠数据集，该项目将有助于区分目前存在的梨亚地层和更大的北极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.