Collaborative Research: A new appraisal of tectonic mobility in the northern Cordillera using connections between the Coast Mountains batholith and Alberta foreland basin

合作研究：利用海岸山脉岩基和阿尔伯塔前陆盆地之间的联系对北部科迪勒拉山脉的构造活动性进行新评估

• 批准号: 2142272
• 负责人: George Gehrels
• 金额: $ 24.27万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-05-15 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2142272&HistoricalAwards=false
• 关键词: Collaborative; Research; new; appraisal; tectonic

Western North America is made up of a collage of exotic terranes – blocks of crust that originated in other locations and were later accreted to the continental margin. Myriad studies have been performed to reconstruct the geologic and geographic histories of these blocks and to develop a chronology of how western North America was assembled. One of the enduring controversies is how far-travelled are some of these terranes. In particular, researchers debate the distance that one exotic block – the Insular superterrane – has been translated. Some argue that it has migrated 1500 kilometers northward – and perhaps eastward – along the North American margin, while others believe it has always remained near its present-day latitude. We propose to evaluate these end-member hypotheses by looking for connections between zircons crystallizing in the Coast Mountains batholith (part of the Insular superterrane) and those that have been recycled into sedimentary rocks of interior Canada. The presence or absence of the distinctive Coast Mountains batholith zircon fingerprint in rocks at similar latitudes will either refute or support the idea that the Coast Mountains were far away at the time of deposition of the targeted sedimentary strata. The proposed research will support students at the undergraduate and graduate levels, as well as a postdoctoral scholar. It will broaden and diversify the STEM workforce through promotion of early career female scientists and the inclusion of underrepresented minority students from Hispanic-serving institutions. One of the most critical unresolved questions in the tectonics of the North American Cordillera concerns the degree of tectonic mobility of terranes during Late Jurassic and Cretaceous time. End-member hypotheses posit that terranes presently located in British Columbia and southeast Alaska were either: 1) translated from the latitude of (Baja) California, and perhaps outboard of the Mezcalera Ocean basin, or 2) have remained near their present position and along the continental margin. The debate between the two forms the basis for the enduring “Baja-BC” controversy, which has been reinvigorated by discussion in recently published syntheses. We will test these end-member hypotheses by determining whether detrital zircons in foreland basin strata of Alberta, Canada (part of stable North America) were derived from the Coast Mountains batholith (CMB; part of the purportedly mobile terrane). This test is enabled by the recent recognition that zircons from igneous rocks of the CMB are isotopically and geochemically distinct from other coeval arcs along the margin (e.g. the Sierra Nevada and Idaho batholiths). Our study will: (1) define zircon age, Hf isotopic composition and trace element trends in plutons of the CMB, (2) generate similar data for plutons of the Omineca belt (a second suite of Cretaceous plutons in British Columbia), and (3) compare these igneous records with new studies of zircons in Cretaceous-Paleogene strata of the foreland basin in the northern Cordillera. Establishing connections between the CMB and inland foreland basin strata would provide strong support for models that invoke limited tectonic mobility, whereas the lack of such connections would support models that involve large-scale north-south and/or east-west displacements.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.

北美西部由异国情调的地体拼贴而成--起源于其他地点、后来增生到大陆边缘的地壳块体。为了重建这些地块的地质和地理历史，并制定北美西部如何组装的年表，已经进行了无数的研究。其中一个持久的争议是，其中一些人的旅行距离有多远。特别是，研究人员争论的距离，一个异国情调的块-岛supernoce-已被平移。有些人认为它已经沿着北美边缘向北迁移了1500公里，也可能是向东迁移，而另一些人则认为它一直保持在今天的纬度附近。我们建议通过寻找海岸山脉岩基（岛屿上的一部分）和那些已被回收到加拿大内陆的沉积岩中的锆石结晶之间的联系来评估这些端员假说。在相似纬度的岩石中是否存在独特的海岸山脉岩基锆石指纹，将反驳或支持海岸山脉在目标沉积地层沉积时很远的观点。拟议的研究将支持本科生和研究生水平的学生，以及博士后学者。它将通过促进早期职业女性科学家和纳入来自西班牙裔服务机构的代表性不足的少数民族学生来扩大STEM劳动力并使其多样化。北美山脉构造学中最关键的未解决问题之一是晚侏罗世和白垩纪时期火山岩的构造活动程度。端元假说认为，目前位于不列颠哥伦比亚省和阿拉斯加东南部的火山岩要么是：1）从（下）加州的纬度平移过来的，也许是在梅斯卡莱拉洋盆的外侧，要么是2）一直保持在它们现在的位置附近，沿着大陆边缘。两者之间的争论形成了持久的“Baja-BC”争议的基础，最近出版的综合论文中的讨论使之重新活跃起来。我们将测试这些端元假说，以确定是否碎屑锆石在前陆盆地地层的阿尔伯塔，加拿大（北美稳定的一部分）来自海岸山脉岩基（CMB的一部分，据称移动的岩石）。最近认识到，来自CMB火成岩的锆石在同位素和地球化学上与沿沿着边缘的其他同时代弧（例如，Sierra内华达州和爱达荷州岩基）不同，这使得该测试成为可能。我们的研究将：（1）确定CMB岩体中的锆石年龄、Hf同位素组成和微量元素趋势，（2）为Omineca带（不列颠哥伦比亚省的第二套白垩纪岩体）生成类似的数据，（3）将这些火成岩记录与北方科迪勒拉前陆盆地的白垩纪-古近纪地层中锆石的新研究进行比较。建立CMB和内陆前陆盆地地层之间的连接将为调用有限的构造活动性的模型提供强有力的支持，而缺乏这种连接将支持涉及大规模南北和/或东西位移的模型。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。