Collaborative Research: RUI: Translation and Accretion of the Yakutat Microplate and Prince William Terrane, Alaska

北美科迪勒拉是通过许多地体的形成、增生和平移而形成的，这种组合大部分发生在白垩纪之后。从那时起，由于太平洋板块与北美板块的相对运动，大部分地形的平移都是向北的。尽管对地形运动和平移进行了数十年的调查，但对于这些地形的起源以及它们在成为阿拉斯加地形合并的一部分之前走了多远，仍然存在许多未知。这个项目带来了新的分析技术来解决这个问题，重点是雅库塔地体，它现在与阿拉斯加南部碰撞，推动了楚格奇山脉的隆起。这项研究验证了雅库特地体起源于太平洋西北部遥远的南部，并在与阿拉斯加南部碰撞之前平行于大陆边缘移动的观点。该项目将通过以下方式促进预期的社会成果：来自代表性不足的少数民族的学生参与STEM；通过为国家公园和国家森林编写小册子，提高公众科学素养和公众对STEM的参与；通过本科生积极参与主要本科院校的研究，培养一支多样化、具有全球竞争力的STEM劳动力队伍。构成阿拉斯加大部分地区的拼贴地的发展和翻译历史存在争议，包括楚格奇和威廉王子地，以及雅库特地。一些场景设想了Chugach和William王子地形的设置或多或少到位，而其他场景（最初基于古地磁数据）则建议长途运输（3000公里）。这些观点的差异是深刻的，但在科迪勒拉，走滑断层上的大规模地体平移可能是一个基本的、未被重视的过程。碎屑锆石的高精度、高体积U/Pb和裂变径迹测年为研究这一问题提供了焦点，通过对科迪勒拉边缘各单元进行地质比较，可以更好地了解平移历史和总偏移量，从而做出严格的预测。初步资料表明，关于丘加奇-威廉王子地体和雅库特地体碰撞带的一些假设需要修正，包括：(1)雅库特地体的浊积岩可能不像以前假设的那样是丘加奇和威廉王子地体的一部分；(2)雅库塔地体的玄武岩基底可能形成于沿北美边缘的张拉环境。这里测试的假设是，雅库特地形向阿拉斯加的运输导致太平洋西北部的边缘被截断，而夏洛特皇后-费尔韦瑟断层系统的滑动可能部分地容纳了1800公里的右平移，这可能是科迪勒拉断层的地质关系所显示的最长偏移之一。本研究的分析方法涉及使用几种技术对碎屑锆石进行分析，其中一些技术是新的和创新的。这些方法包括：(a)通过碎屑锆石的U/Pb来确定最大沉积年龄和物源，包括针对前寒武纪的物源；(b)碎屑锆石的裂变径迹提供了与发掘直接相关的冷却年龄，包括双重定年颗粒（裂变径迹和U/Pb）；(c)碎片拉曼光谱，提供辐射损伤日期；(d)碎屑锆石中的Hf同位素提供地壳特征；(e)岩心边缘测定火成岩和变质岩边缘的年代。确定碎屑锆石的辐射损伤年龄是一种新的方法，有望为碎屑研究提供更深入的见解。虽然锆石是这项工作的核心，但使用地球化学和岩石学的学生项目将侧重于更好地了解与这些地体相关的火成岩的发展。

The North American Cordillera was assembled through the formation, accretion, and translation of a number of terranes and much of this assembly has occurred since the Cretaceous. Since this time, most of the terrane translation was northward due to the relative motion of Pacific plates with North America. Despite decades of investigations on terrane movement and translation much remains unknown about where these terranes originated and how far they traveled before becoming part of the amalgamation of terranes in Alaska. This project brings new analytical techniques to bear on this problem focusing on the Yakutat terrane, which is now colliding with southern Alaska driving the uplift of the Chugach Range. This research tests the idea that the Yakutat terrane originated far to the south in the Pacific Northwest and moved parallel to the continental margin before colliding with southern Alaska. The project would advance desired societal outcomes by participation of students from underrepresented minorities in STEM, increased public scientific literacy and public engagement with STEM through development of brochures for the National Parks and National Forests and development of a diverse, globally competitive STEM workforce through active participation of undergraduate students in research at primarily undergraduate institutions.The development and translation history of the collage of terranes that make up most of Alaska are debated, including the Chugach and Prince William terranes, and Yakutat terrane. Some scenarios envision a setting for the Chugach and Prince William terranes that was more or less in place, while other scenarios (originally based on paleomagentic data) suggest long transport (3000 km). The difference in these ideas is profound, but large-scale translation of terranes on strike-slip faults may be a fundamental and underappreciated process in the Cordillera. High-precision and high-volume U/Pb and fission track dating of detrital zircon has focused the lens with which the problem can be examined, and rigorous predictions can be made by making geological comparisons of units along the Cordilleran margin to better understand translation history and total offset. Preliminary data show a number of assumptions about the Chugach-Prince William terrane and Yakutat terrane collision zone need to be revised, including: (1) turbidites of the Yakutat terrane may not be part of the Chugach and Prince William terranes as previously assumed; and (2) the basaltic basement of the Yakutat terrane may have formed in a transtensional environment along the North American margin. The hypothesis tested here is that transport of the Yakutat terrane to Alaska resulted in a truncated margin in the Pacific Northwest, and slip on the Queen Charlotte-Fairweather fault system may have partly accommodated the 1800 km of dextral translation, which may be one of the longest offsets shown by geological relationships on faults in the Cordillera. The analytical approach of this research involves the analysis of detrital zircon using several techniques, some of which are new and innovative. These approaches include: (a) U/Pb of detrital zircon to determine maximum depositional age and provenance, including targeting Precambrian sources; (b) fission track on detrital zircons to provide cooling ages directly related to exhumation, including double dating grains (fission track and U/Pb); (c) Raman spectroscopy on detrital to provide radiation damage dates; (d) Hf isotopes in detrital zircon to provide crustal signature; and (e) core-rim dating to date igneous and metamorphic rims. Determining radiation damage ages on detrital zircon is a new approach that promises to provide deeper insight into detrital studies. Although zircon is central to this effort, student projects that use geochemistry and petrology will focus on better understanding the development of the igneous rocks associated with these terranes.