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

基本信息

批准号：
2405553
负责人：
Emily Cooperdock
金额：
$ 31.12万
依托单位：
Brown University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2023
资助国家：
美国
起止时间：
2023-10-01 至 2025-02-28
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2405553&HistoricalAwards=false
关键词：
Collaborative Research Evaluating Exhumation History

项目摘要

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链，其中一个板块被拖到另一个板块下方，将旧地壳回收到地幔，并通过火山作用形成新的大陆地壳。围绕这些系统的一个核心问题是，这些过程是否发生在深层。俯冲带对地表观测到的过程的影响尤其引起争议，因为其他地区的岛弧隆起和折返的驱动因素有多种。从深层构造驱动因素到气候与地表相互作用，折返率和侵蚀估计存在数量级的差异，在许多地方，弧折返历史很难研究，因为它可能会被后来的热或物理过程所覆盖。阿留申弧的独特之处在于它包括 50 多个由活火山和非活火山组成的岛屿，从阿拉斯加到俄罗斯超过 1,900 英里，并且受到次生事件的影响有限。此外，它还有一座火山。历史跨越了 5000 万年，因此过去火山的古老岩浆室如今暴露在岛屿表面，这些深成岩记录了过去岛屿隆起、折返和侵蚀的记录，可以解决以下关键问题：随着时间的推移，阿留申群岛抬升了多少？抬升和随后的侵蚀是持续的还是周期性的？具体来说，这些问题的答案将揭示这一点。板块尺度过程与隆起之间的联系；侵蚀的时间和程度，对北太平洋的沉积物和地球化学输入；以及深成体折返率、地球化学和侵位深度之间的关系。测试了四十多年来有关俯冲带演化的基本原理，该研究将为现有广泛的地球化学和地球动力学研究做出新的贡献，该奖项支持新的 PI 并参与其中。代表性不足的少数民族学生和教师，从本科生到 K-12 年级，为了量化阿留申群岛经历地表隆起和侵蚀的时间和程度，将对来自约 10 个弧长 870 英里的岛屿的深成岩样本进行分析。这项工作将把中阿留申群岛的折返历史置于 1) 区域构造和俯冲带过程的驱动力以及 2) 地球化学的背景下。为了回答这些问题，之前从阿留申群岛中部取样并充分表征的深成岩将通过深成岩结晶年龄、侵位深度和 2 个或更多不同温度计进行表征。热敏感性（例如磷灰石和/或锆石、(U-Th)/He 和/或裂变径迹技术，特别是热年代学技术的使用）。同一样本中具有不同温度敏感性的多个计时器，可以限制折返率，并用于估计随时间的侵蚀率，将热年代学数据与安置深度相结合将有助于限制该时间段内侵蚀的材料量。然后，可以将这些数据在时间和空间上与先前提出的抬升驱动因素联系起来，包括板块旋转、会聚角度和速率的变化，或吸积棱镜的发展。该奖项反映了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，NSF 的法定使命被认为值得支持。