CAREER: Shallow angle subduction and tectonic underplating of magmatic arc root zones: a recipe for high-flux magmatism?

该项目评估了一种假设，即大陆下方物质的浅角俯冲，并将该物质粘在覆盖板块的底部，可能导致火成岩活动的“爆发”（即，更多的火山爆发和地下侵入）。这一假说预测，俯冲应不久之前，在上板块岩浆活动的上升，上板块岩浆活动应在空间上重叠的底侵区。为了验证这一假设，本研究集中在两个地点，俯冲相关的岩石下的火山-深成物质：克拉马斯山（北方加利福尼亚州南部俄勒冈州）和中部加州海岸山脉。这项工作有可能改变对浅角俯冲和上板块岩浆活动之间关系的理解。这项研究解决了一个具有全球意义的问题，即浅角俯冲是大陆地壳的净生产者还是破坏者，这对地壳如何随着时间的推移而生长（或收缩）有影响。 本项目：1）为大约54名学生提供实地研究经验和导师-学生和同行-学生指导，增加这些学生在STEM继续学习和职业生涯的可能性（科学、技术、工程和数学）领域; 2）暴露了两个代表性不足的少数民族本科研究人员和一个后-学士学位研究员每年现代分析技术和活跃的研究人员在美国; 3）加速首席研究员作为教师学者的职业发展，建立新的和加强现有的合作; 4）制作招聘和宣传材料，旨在提高STEM领域代表性不足的群体的知名度; 5）与明尼苏达州双子城地区的小学生保持积极的外展计划。本项目旨在通过调查和系统输入的质量平衡（例如，构造和岩浆底侵作用）和产出（构造侵蚀和拆沉作用）。浅角部位（即，倾角小于30度的俯冲带，约占活跃俯冲带的10%，是该项目的一个特别重点，因为这些地区的特点是地壳快速生长和破坏。例如，熔融肥沃的弧前材料可能被输送到弧根区在板变浅的过程中，提供了一个可能的催化剂的高通量岩浆在覆盖板。考虑到这一点，这项工作的研究目标是测试的假设，即构造底侵的弧前物质直接下方的活动弧在浅俯冲事件可以触发事件的高通量岩浆弧关闭之前。 这一研究的科学价值包括：1）改变我们对浅俯冲、构造底侵作用和弧岩浆作用之间关系的认识的潜力; 2）限制了浅俯冲系统的构造侵蚀和底侵作用速率，以便与现代系统进行比较;（3）明确了各层的原始位置和岩性对比，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，更广泛的影响审查标准。

This project evaluates the hypothesis that shallow-angle subduction of material beneath a continent, and sticking that material to the base of the overriding plate, can cause a "flare-up" in igneous activity (i.e., more voluminous volcanic eruptions and subsurface intrusions). This hypothesis predicts that subduction should shortly precede an uptick in upper plate igneous activity and that upper plate magmatism should spatially overlap the underplated region. To test this hypothesis, this research focuses on two sites where subduction-related rocks underlie volcanic-plutonic materials: the Klamath Mountains (northern California-southern Oregon) and the central California Coast Ranges. This work has the potential to transform understanding of the relationships between shallow-angle subduction and upper plate magmatism. This research addresses the globally significant question of whether shallow-angle subduction is a net producer or destroyer of continental crust, which has implications for how the crust grows (or shrinks) over time. This project: 1) provides a field-based research experience and instructor-student and peer-student mentoring for approximately 54 students, increasing the likelihood that these students will pursue continued study and careers in the STEM (science, technology, engineering and mathematics) fields; 2) exposes two underrepresented minority undergraduate researchers and one post-baccalaureate researcher per year to modern analytical techniques and active researchers across the United States; 3) accelerates the career development of the principal investigator as a teacher-scholar, building new and enhancing existing collaborations; 4) produces recruitment and promotional materials aimed at increasing the visibility of underrepresented groups in STEM fields; and 5) sustains an active outreach program with elementary school students of the greater Twin Cities, Minnesota region. This project aims to clarify the processes that control the long-term stability of continental crust through investigation and mass balance of system inputs (e.g., tectonic and magmatic underplating) and outputs (tectonic erosion and delamination). Sites of shallow angle (i.e., a dip of less than 30 degrees) subduction, representing about 10% of active subduction zones, are a particular focus of this project, as rapid crustal growth and destruction characterize these areas. For example, melt-fertile forearc materials are likely conveyed into arc root zones during the slab shallowing process, providing a possible catalyst for high-flux magmatism in the overriding plate. With this in mind, the research objective of this work is to test the hypothesis that tectonic underplating of forearc materials directly beneath active arcs during shallow subduction events can trigger episodes of high-flux magmatism prior to arc shutoff. The scientific merits of this research include: 1) the potential to transform our understanding of the relationships between shallow subduction, tectonic underplating, and arc magmatism; 2) constraining the rates of tectonic erosion and underplating in exhumed shallow subduction systems for comparison with modern systems; and 3) clarifying the original positions of, and lithologic correlations within, the central California Coast Ranges and the central Klamath Mountains.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.