Collaborative Research: Evaluating the Exhumation History of the Aleutians with Zircon and Apatite Thermochronology

合作研究：利用锆石和磷灰石热年代学评估阿留申群岛的发掘历史

• 批准号: 1949160
• 负责人: Claire Bucholz
• 金额: $ 3.83万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-03-15 至 2023-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1949160&HistoricalAwards=false
• 关键词: Collaborative; Research; Evaluating; Exhumation; History

Island arcs are chains of volcanic islands that form at subduction zone plate boundaries where one plate is being dragged beneath another, recycling old crust to the Earth’s mantle and creating new continental crust through volcanism. A central question surrounding these systems is whether processes that occur deeply in the subduction zone affect processes that are observed on the surface. This is especially debated for what drives surface uplift and related island arc exhumation and erosion. Uplift and exhumation of island arcs in other localities have been attributed to a variety of factors, from deep tectonic drivers to climate-surface interactions, with exhumation rates and erosion estimates that vary by orders of magnitude. In many locations, the arc exhumation history is difficult to study because it may be overprinted by later thermal or physical processes. The Aleutian Arc is unique in that it includes over 50 islands composed of both active and inactive volcanoes over 1,900 miles from Alaska to Russia, and has limited overprinting by secondary events. In addition, it has a volcanic history that spans 50 million years, so that the ancient magma chambers of past volcanoes are now exposed on the islands’ surfaces today. These plutonic rocks hold a record of past island uplift, exhumation, and erosion that can address key questions regarding: When were the Aleutians uplifted? When and how much has been eroded through time? Was uplift and subsequent erosion constant or cyclical? How does it vary geographically along the length of the arc? Specifically, the answers to these questions will shed light on the link between plate-scale processes and uplift; the timing and magnitude of erosion, contributing sediment and geochemical inputs to North Pacific; and the relationship between plutonic exhumation rates, geochemistry, and emplacement depth. The Aleutians have functioned as a natural laboratory to test fundamental principles regarding subduction zone evolution for more than four decades. This study will make a novel contribution to the existing extensive geochemical and geodynamic research. In terms of Broader Impacts, this award supports a new PI and engages underrepresented minority students and teachers, from the undergraduate through K-12 level. In order to quantify when and by how much the Aleutians experienced surface uplift and erosion, plutonic samples from ~10 islands that span 870 miles of arc length will be analyzed for emplacement depth and subsequent uplift rates. This work will place the exhumation history of the Central Aleutians in the context of 1) driving forces involving regional tectonics and subduction zone processes; and 2) geochemical inputs to the N. Pacific via erosion of arc material. In order to answer these questions, previously sampled and well-characterized plutonic rocks from across the central Aleutians will be characterized by pluton crystallization age, emplacement depth, and 2 or more thermochronometers with different thermal sensitivities (e.g., apatite and/or zircon, (U-Th)/He and/or fission track). Thermochronology techniques, particularly the use of multiple chronometers with different temperature sensitivities within the same sample, can constrain exhumation rates and be used to estimate erosion rates over time. Coupling the thermochronological data with emplacement depth will help constrain the amount of material eroded over that time. The timing and geographic trends revealed by these data can then be related in time and space to previously proposed drivers for uplift, including plate rotation, change in convergence angle and rate, or the development of an accretionary prism.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.

岛弧是在俯冲带板块边界形成的火山岛的链条，其中一个盘子被拖到另一个板块下方，将旧地壳回收到地球的地幔上，并通过火山主义形成新的连续地壳。这些系统围绕这些系统的一个核心问题是，俯冲带深层发生的过程是否会影响在表面上观察到的过程。这是关于驱动表面隆升和相关岛屿弧挖掘和侵蚀的原因尤其令人震惊的。在其他地方的岛屿弧的隆起和挖掘归因于各种因素，从深层构造驱动因素到气候表面相互作用，其发掘速率和侵蚀估计因数量级而异。在许多位置，弧挖掘历史记录很难研究，因为它可能被以后的热过程或物理过程所覆盖。阿留申弧线的独特之处在于它包括50多个岛屿，这些岛屿由从阿拉斯加到俄罗斯的1,900英里超过1,900英里组成，并且因次要事件而有限。此外，它的火山历史跨越了5000万年，因此现在过去火山的古老岩浆腔室在今天的岛屿表面上暴露在岛上。这些岩石岩石记录了过去的岛屿隆升，挖掘和侵蚀的记录，这些岩石可以解决有关：阿留申者何时提升的关键问题？随着时间的流逝，何时又侵蚀了多少？隆起和随后的侵蚀常数还是周期性？它如何沿弧的长度在地理上变化？具体而言，这些问题的答案将阐明板规尺度过程与隆升之间的联系；侵蚀的时机和幅度，促成北太平洋的沉积物和地球化学输入；以及冥王星发掘速率，地球化学和安置深度之间的关系。阿留申者一直是一项自然实验室，用于测试有关俯冲带进化的基本原理，已有四十年多了。这项研究将为现有的广泛的地球化学和地球动力学研究做出新的贡献。在更广泛的影响方面，该奖项支持新的PI，并从本科到K-12级的少数族裔学生和老师参与了不足的少数民族学生和老师。为了量化Aleutians在何时及时经历了多少表面隆起和侵蚀，将分析跨越870英里长度长度的约10个岛屿的腔体样品，以分析增强深度和随后的升高速率。这项工作将在1）涉及区域构造和俯冲带过程的驱动力的背景下将中央阿留申群岛中部的挖掘历史放置； 2）通过弧形侵蚀到太平洋猪笼草的地球化学输入。为了回答这些问题，来自阿留申岛中部的先前采样且特征良好的plut岩的特征是plut子结晶的年龄，增压深度，以及具有不同热敏感性的2个或更多的热化学计（例如，apatite和/或zircon和zircon，（u-th）/he He and He and He and/he and或fistion Track）。热量技术技术，尤其是在同一样品中使用不同温度灵敏度的多个天文组织的使用，可以限制发掘速率，并用于估计随着时间的推移估算侵蚀速率。将热量数据与安置深度耦合将有助于限制这段时间发出的材料量。然后，这些数据揭示的时间和地理趋势可以在时间和空间上与先前提出的升高驱动程序相关联，包括板旋转，收敛角度和速率的变化，或开发增生性Prism的发展。该奖项反映了NSF的法定任务，并通过使用该基金会的知识优点和广泛的criperia criperia criperia criperia criperia criperia criperia criperia criperia criperia criperia criperia criperia rection the奖项。