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

北美西部是由奇异的地体拼贴而成的，这些地体是起源于其他地方的地壳块，后来又附着到大陆边缘。人们进行了无数的研究，以重建这些区块的地质和地理历史，并建立北美西部是如何组装的年表。其中一个持久的争议是，其中一些地体的旅行距离有多远。特别是，研究人员讨论了一个奇异的地块--岛状超地体--被平移的距离。一些人认为，它沿着北美边缘向北--也许是向东--迁移了1500公里，而另一些人则认为，它一直保持在今天的纬度附近。这些假说将通过寻找海岸山脉岩基(岛状超地体的一部分)中结晶的锆石和那些被回收成加拿大内陆沉积岩的锆石之间的联系来评估。在类似纬度的岩石中存在或不存在独特的海岸山脉岩基锆石指纹，将驳斥或支持海岸山脉在目标沉积层沉积时距离很远的观点。拟议的研究将支持本科生和研究生，以及博士后学者。它将通过促进职业生涯早期的女科学家和纳入拉美裔服务机构中代表性不足的少数族裔学生来扩大和多样化STEM劳动力队伍。北美科迪勒拉构造中最关键的悬而未决的问题之一是晚侏罗世和白垩纪时地体的构造活动性程度。最终成员假说认为，目前位于不列颠哥伦比亚省和阿拉斯加东南部的地体有：1)从加利福尼亚州(Baja)纬度转换而来，可能位于梅兹卡莱拉洋盆的外侧；或2)保持在目前位置附近并沿大陆边缘。两者之间的辩论构成了持久的“巴哈-公元前”争议的基础，最近发表的论文中的讨论重新激活了这一争议。将通过确定加拿大阿尔伯塔省(稳定北美的一部分)前陆盆地地层中的碎屑锆石是否来自海岸山脉岩基(CMB；据称是活动地体的一部分)来检验这些终端成员假说。这项测试是由于最近认识到来自CMB火成岩的锆石在同位素和地球化学上不同于边缘的其他同纪弧(例如内华达山脉和爱达荷州浴岩)。这项研究将：(1)确定CMB深成岩中的锆石年龄、Hf同位素组成和微量元素趋势；(2)为Omineca带(不列颠哥伦比亚省第二套白垩纪深成岩)的深成岩提供类似的数据；(3)将这些火成岩记录与科迪勒拉北部前陆盆地白垩纪-古近纪地层中的锆石新研究进行比较。在CMB和内陆前陆盆地地层之间建立联系将为引起有限构造流动性的模型提供强有力的支持，而缺乏这种联系将支持涉及大规模南北和/或东西位移的模型。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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. These hypotheses will be evaluated 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. These end-member hypotheses will be tested 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). The 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.