Rapid cycling of magma compositions in continental arc systems

这个项目的目的是描述与火山化学成分变化相关的时间尺度，这些火山爆发在大陆边缘，一个构造板块俯冲到另一个板块之下（即俯冲带）。了解化学变化的时间尺度将有助于深入了解火山喷发的岩浆系统。该项目将重点研究俯冲带火山系统的化学成分是否可以在不到10万年的时间尺度上发生变化。为了回答这个问题，该项目将调查一系列火山灰，这些火山灰来自6500万年前美国西海岸爆发的火山，并在700万年的时间里沉积在德克萨斯州西部。该项目的主要目标包括创建火山成分的高分辨率记录，以更好地了解火山作用如何以及为什么随时间变化。除了填补目前对火山和岩浆系统的理解的重要空白之外，该项目还将对理解战略自然资源的产生产生影响，这对于从碳氢化合物向更多可再生能源基础的能源过渡至关重要。特别是，对铜和锂矿床的见解可能会从这个项目中产生。该项目的一部分内容还包括开设一门关于自然资源的科学、经济和政策的课程，这将有助于教育地球科学家了解能源转型所需的自然资源。大陆弧火山作用产生的岩浆成分种类繁多，但成分变化的速度尚不清楚。了解弧岩浆的平均成分在空间和时间上是如何变化的，可以为弧环境下跨地壳岩浆系统的物理特性提供见解。该项目关注的基本问题是岩浆弧的组成是否可以在小于10-100 kyr的时间尺度上系统地变化。一份高分辨率的记录显示，火山灰已经变成了膨润土，这将有助于重建弧组成的详细历史。四个主要目标将有助于回答这个问题。第一个目标是检查膨润土中的成岩信号，以评估膨润土形成过程中的元素流动性。第二个目标是重建经过改变的膨润土的灰原岩组成，以便创建弧组成随时间变化的记录。第三个目标是分析火山矿物以获得额外的岩石成因信号，从而了解岩浆过程。前三个目标的结果将使岩浆通量、侵蚀、构造和地壳厚度如何影响跨地壳岩浆和热传递的时间尺度和过程的模型成为可能。方法包括利用μXRF进行膨润土成分制图，利用ICPMS进行膨润土微量元素分析，利用EPMA分析火山矿物成分。除了解决基本问题外，该项目还将对了解自然资源（如Li和Cu）、了解地表和沉积过程以及了解火山灰的生物地球化学和环境影响产生影响。更广泛的社会影响将包括学生参与一个改善城市公园可达性的项目和开发一门关于重要矿物资源的课程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to characterize timescales associated with changes in the chemical composition of volcanoes that erupt on the edges of continents where one tectonic plate dives beneath another (i.e., subduction zones). Understanding timescales for chemical changes will provide insights into magma systems that feed volcanic eruptions. This project will focus on the question of whether the chemistry of volcanic systems in subduction zones can change on timescales less than 100,000 years. In order to answer this question, this project will investigate a sequence of volcanic ash derived from volcanoes that erupted along the west coast of the US over 65 million years ago and was deposited in west Texas over a 7-million-year period. Major goals of the project include creating a high-resolution record of volcanic composition to better understand how and why volcanism changes over time. In addition to filling important gaps in current understanding about volcanoes and magmatic systems, this project will also have implications for understanding the generation of strategic natural resources that will be critical for the energy transition to from hydrocarbons to a more renewable energy base. In particular, insights into copper and lithium deposits may arise from this project. Part of this project will also involve developing a course on the science, economics, and policy of natural resources, which will help educate earth scientists on the natural resources necessary for the energy transition. Continental arc volcanism generates a wide diversity of magma compositions, but the tempos of compositional variation are unclear. Understanding how the average composition of arc magmas varies in space and time may provide insights into the physics of the transcrustal magmatic system in arc settings. This project focuses on the fundamental question of whether the composition of a magmatic arc can systematically change on timescales of less than 10-100 kyr. A high-resolution record of ash that has been altered into bentonite will enable reconstruction of a detailed history of arc composition. Four major goals will contribute to answering this question. The first goal is to examine diagenetic signals in bentonites in order to assess elemental mobility during bentonite formation. The second goal involves reconstructing ash protolith compositions from the altered bentonites in order to create a record of arc composition over time. A third goal is to analyze volcanic minerals for additional petrogenetic signals to inform about magmatic processes. Results from these first three goals will enable models of how magmatic flux, erosion, tectonism, and crustal thickness influence timescales and processes of transcrustal magma and heat transfer. Methods will include using μXRF for compositional mapping of bentonites, ICPMS for trace element analyses of bentonites, and EPMA analyses of volcanic mineral compositions. In addition to addressing the fundamental question, this project will also have implications for understanding natural resources such as Li and Cu, for understanding surface and depositional processes, and for understanding the biogeochemical and environmental impacts of volcanic ash. Broader societal impacts will include student participation in a project to improve the accessibility of urban parks and development of a course on critical mineral resources.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.