Detrital Zircon geochronology applied to Cordilleran Tectonics

这项为期5年的研究计划是一项长期努力的一部分，目的是揭示北美西部山脉(N.A.Cordillera)复杂的构造历史。北卡罗来纳州科迪勒拉是地球上研究最深入的山脉之一，也是研究深部地幔、岩石圈、水圈和大气之间反馈关系的重要自然实验室。尽管人们对N.A.科迪勒拉的演变有了很多了解，许多工作人员也在关注它的起源，但仍然有一些重要的根本性问题和矛盾仍然没有得到解决或解释不力。解决这些问题对国际地球科学界非常重要，因为北美作为研究大陆板块构造的天然实验室发挥着重要作用。如果我们不了解地球上研究最充分的大陆，那么我们如何推断到世界上其他不太了解的地区呢？北美大地构造中遗留下来的最重要的问题：1.巴哈-公元前争议，2.地体过程：地体是如何以及在哪里形成、运输和吸积的？3.造山和岩浆旋回性：为什么岩浆弧关闭并爆发，这与地体过程有何关系？4.俯冲作用：俯冲如何启动和传播，速度是多少，这一过程与地体过程有何关系？这些悬而未决的问题都是我们理解北美西部过去5亿年构造演化的核心。此外，这些问题的答案影响着科学家在全球范围内对大陆构造的总体看法。我的团队未来五年研究的一个关键成果是解决了以古地磁数据和基本地质观测为中心的巴哈-公元前争议。古地磁数据要求地体从南向北进行大规模的迁移，而地质观测则被认为排除了这种侧向位移。我们正在通过使用高分辨率碎屑锆石年代学作为地壳碎片横向运动的独立约束来协调地质和古地磁数据。这一领域的成功将改变北美西部的构造史，并有助于解决上述问题2和3。该计划的另一个重要成果将是将海达瓜伊岛确立为北美潜水启动的天然实验室。我们的研究计划将提供第一批数据，记录与北美西部之下太平洋板块俯冲相关的抬升和侵蚀。我们将知道俯冲开始的时间、传播速度以及对俯冲板块的影响。这项研究计划对加拿大很重要，因为它提高了加拿大作为地球科学变革性推动者的形象，同时培训了将转移知识和技能的加拿大HQP。

This 5 year research program is part of a long-term effort to unravel the complex tectonic history of the mountains of western North America (N.A. Cordillera). The N.A. Cordillera is one of the most intensively studied mountain belts on earth and a key natural laboratory for studying feedback relationships between the deep mantle, lithosphere, hydrosphere and atmosphere. Although much is known about the evolution of the N.A. Cordillera, and many workers are focused on its genesis, there are still important fundamental questions and contradictions that remain unresolved or poorly explained. Resolving these, is important to the international earth science community because of North America’s important role as a natural laboratory for research into continental plate tectonics. If we do not understand the best-studied continent on earth then how do we extrapolate to other parts of the world that are less well understood? The most important problems remaining in North American tectonics: 1. The Baja - BC controversy, 2. Terrane processes: How and where are terranes made, transported and accreted? 3. Orogenic and magmatic cyclicity: Why do magmatic arcs shut down and flare up and how is this related to terrane processes 4. Subduction initiation: How does subduction initiate and propagate, what are the rates, and how does this process relate to the terrane processes? These unresolved questions are all central to our understanding of the last half a billion years of western North America’s tectonic evolution. In addition, the answers to theses questions impacts how scientists view continental tectonics in general, at the global scale. A key outcome of the next five years of research by my group is the resolution of the The Baja-BC controversy, which is centered on paleomagnetic data and basic geologic observations. The paleomagnetic data require large-scale south to north transport of terranes whereas the geologic observations are seen as precluding such lateral displacements. We are reconciling the geological and paleomagnetic data via the use of high-resolution detrital zircon geochronology as an independent constraint on the lateral movement of crustal fragments. Success in this area will change the tectonic history of western North America and contribute to resolving questions 2 and 3 above. Another important outcome of this program will be to establish Haida Gwaii as North America’s natural laboratory for subduction initiation. Our research program will provide the first data that records the uplift and erosion associated with the initiation of Pacific plate subduction beneath western North America. We will know when subduction initiated, propagation rate and what the effects on the overriding plate are. This research program is important to Canada because it raises Canada’s profile as a transformative agent in the earth sciences while training Canadian HQP who will transfer knowledge and skills.