Rapid cycling of magma compositions in continental arc systems

该项目旨在描述与火山化学成分变化相关的时间尺度，这些火山在大陆边缘喷发，其中一个构造板块潜入另一个构造板块之下（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爆发的岩浆系统。该项目将重点研究俯冲带火山系统的化学性质是否会在不到10万年的时间尺度上发生变化。为了回答这个问题，本项目将调查6500多万年前美国西海岸沿着火山喷发产生的火山灰序列，这些火山灰在700万年的时间里沉积在西德克萨斯州。该项目的主要目标包括创建火山成分的高分辨率记录，以更好地了解火山活动如何以及为什么会随着时间的推移而变化。除了填补目前对火山和岩浆系统的认识方面的重要空白外，该项目还将对了解战略自然资源的产生影响，这对于能源从碳氢化合物过渡到更可再生的能源基础至关重要。特别是，对铜和锂矿床的见解可能会从这个项目中产生。该项目的一部分还将涉及开发一门关于自然资源的科学、经济学和政策的课程，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了多种多样的岩浆成分，但成分变化的节奏尚不清楚。了解弧岩浆的平均成分如何在空间和时间上变化，可能会为了解弧环境中的穿壳岩浆系统的物理学提供见解。该项目的重点是一个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的基本问题。一个高分辨率的记录灰已被改变成膨润土将能够重建电弧成分的详细历史。四个主要目标将有助于回答这个问题。第一个目标是检查在膨润土的成岩信号，以评估膨润土形成过程中的元素流动性。第二个目标涉及重建灰原岩组成的蚀变榴辉岩，以创造一个记录弧组成随时间的推移。第三个目标是分析火山矿物，以获得更多的岩石成因信号，从而了解岩浆过程。从这前三个目标的结果将使模型的岩浆流量，侵蚀，构造作用和地壳厚度如何影响时间尺度和过程的穿壳岩浆和热传递。方法将包括使用μXRF进行钙钛矿的成分制图，ICPMS进行钙钛矿的微量元素分析，以及EPMA分析火山矿物成分。除了解决基本问题外，该项目还将对理解Li和Cu等自然资源、理解地表和沉积过程以及理解火山灰的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项目，以改善城市公园的可达性和关键矿产资源的课程开发。这个奖项反映了NSF的法定使命，并已被认为是值得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的支持。

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.