Structural Architecture and Evolution of the Southern Flank of the Brooks Range Fold and Thrust Belt, Arctic Alaska

阿拉斯加北部布鲁克斯山脉南侧有一个与断层有关的宽广变形带，名为片岩带，东西绵延600多公里。该断裂带在形成侧翼沉积盆地、南部的育空-科尤克盆地和布鲁克斯山脉以北的科尔维尔盆地中发挥了基本作用。它也是阿拉斯加南部和阿拉斯加北部之间的主要构造，阿拉斯加的地质历史与太平洋板块边缘有关，而阿拉斯加北部的历史与北冰洋的板块构造有关。尽管它的物理范围令人印象深刻，但关于它的确切年龄的问题，以及关于它为什么和如何发展的假设，都存在争议。该项目将研究这一断裂带的地质和变形历史，与一个旨在了解北极地区地质的瑞典国际项目共享后勤。这项拟议的研究代表着对基础科学的贡献，将提高我们对北极地质的理解，北极是地球上仅存的边疆之一。目前全球对北极的兴趣使该地区成为国际合作的绝佳场所，并为研究生提供了从事实地研究、学习最先进的分析技术和建立职业生涯的独特机会。对北极地球科学和国际合作方面的研究生进行培训有助于为美国，特别是北极地区培养一支多元化的、具有全球竞争力的STEM(科学、技术、工程和数学)劳动力队伍。随着北极国家根据国际条约规划其近海经济区，国际交流与合作是美国的首要任务。拟议的研究还将编制地图和数据汇编，这些地图和数据汇编将有助于社会各阶层广泛了解自然资源，包括矿物和碳氢化合物、潜在的地质灾害和土地利用，并有助于了解北极国家公园之门的地质情况。出于国家安全考虑，更多地了解北极地区也很重要。阿拉斯加北侧的布鲁克斯山脉造山带是一条侏罗纪至早白垩世的地壳缩短带，具有典型的由被动边缘层序和异地洋弧层序组成的冲断带构造。布鲁克斯山脉的构造更深、多变质的核心现在被认为包括北冰洋喀里多尼德和波罗的海蒂马尼德的一部分，北冰洋的开放使它们变成了现在的位置。片岩带被定义为一个穿透性变形带，其组构和年龄(基于40Ar/39Ar年代学)被前人以截然不同的方式解释。我们提议的工作将检验假设，并解决关于这条带的年龄和起源的问题。地质填图结合中、微观构造工作，包括研究石英晶格的优先取向，将允许沿走向比较带内的变形，并确定它是代表逆冲还是正常意义上的剪切。用40Argon/39Argon方法进行的热年代学断面和变质锆石生长的铀铅定年将为变形和变质年龄提供依据。磷灰石裂变径迹年龄将使我们能够确定导致片岩带岩石显著和独特暴露的大规模新生代构造的几何形状。拟议的工作提供了一个独特的机会，可以与瑞典研究理事会资助的一项为期5年的活动合作，它将有助于侧重于了解北冰洋起源的广泛国际努力。它还为我们提供了与涉及在阿拉斯加州部署EarthScope？S可移动阵列的实质性科学任务合作的机会，这最终将为本研究提供岩石圈背景。

A broad zone of fault-related deformation, called the Schist Belt, stretches East-West for more than 600 kilometers along the southern side of the Brooks Range in northern Alaska. This fault zone played a fundamental role in the formation of flanking sedimentary basins, the Yukon-Koyukuk Basin to the south and the Colville Basin to the north of the Brooks Range. It is also the main structure separating southern Alaska, with a geologic history tied to the Pacific plate margin, from northern Alaska, whose history is tied to plate tectonics in the Arctic Ocean. Despite its impressive physical extent, questions about its exact age and hypotheses about why and how it developed are debated. This project will study the geology and deformation history of this fault zone, sharing logistics with an international Swedish project aimed at understanding the geology of the Arctic region. The proposed research represents a contribution to basic science that will improve our understanding of the geology of the Arctic, one of the last remaining frontiers on earth. Current global interest in the Arctic makes this region a superb arena for international collaborations and offers a unique opportunity for graduate students to engage in field-based research, learn state-of-the-art analytical techniques and build their careers. Training graduate students in Arctic geoscience and international collaboration contributes to a diverse, globally competitive STEM (science, technology, engineering and mathematics) workforce for the U.S., particularly in the Arctic. International communication and collaboration is a top priority for the U.S. as Arctic nations chart their offshore-extended economic zones based on international treaties. The proposed research will also produce maps and data compilations that will represent contributions that will be useful to a broad cross-section of society as related to natural resources, including both mineral and hydrocarbons, potential geologic hazards and land-use, as well as contributing to knowledge of the geology of the Gates of the Arctic National Park. Greater understanding of the Arctic region is also important to national security considerations. Along its northern side, the Brooks Range orogen of Arctic Alaska is a Jurassic to Early Cretaceous belt of crustal shortening characterized by a classic thrust belt architecture consisting of imbricated passive margin sequences and allochthonous oceanic arc sequences. The structurally deeper, polymetamorphic core of the Brooks Range is now understood to include portions of the Arctic Caledonides and the Baltic Timanides, translated to their current position by the opening of the Arctic Ocean. The Schist Belt is defined as a zone of penetrative deformation whose fabrics and age (based on 40Argon/39Argon geochronology) are interpreted in remarkably different ways by previous workers. Our proposed work will test hypotheses and address questions about the age and origin of this belt. Geologic mapping coupled with meso- and microstructural work, including the study of quartz lattice preferred orientations, will permit along strike comparisons of deformation within the belt and determine if it represents thrust or normal sense shear. Thermochronology transects using 40Argon/39Argon methods and Uranium-Lead dating of metamorphic zircon growth will place brackets on the age of deformation and metamorphism. Apatite fission track dating will allow us to define the geometry of large-scale Cenozoic structures that led to the remarkable and unique exposures of Schist Belt rocks. The proposed work provides a unique opportunity to join efforts with a 5-year campaign funded by the Swedish Research Council and it will contribute to the broad international effort focused on the understanding the origin of the Arctic Ocean. It also offers us the opportunity to collaborate with a substantial scientific mission involving the deployment of EarthScope?s Transportable Array across the state of Alaska, which will ultimately provide a lithospheric context for this study.