Pre-eruptive magma assembly, evolution and associated magma fluxes at arc calderas: insights from the active Cerro Blanco Volcanic Complex, Catamarca, Argentina.

火山爆发对社会的影响从局部到全球。在地方和区域，社会和基础设施可能遭到破坏。在全球范围内，这样的火山喷发会影响全球气候。历史上的例子包括1815年的坦博拉和1991年的皮纳图博。这些火山喷发发生在俯冲带，也就是地球构造板块交汇的地方。它们还会形成火山口，岩浆库上方的地面坍塌，形成一个大洼地。这样的火山爆发每世纪发生几次，因此引起了社会的关注。在努力了解这种火山口火山的潜在威胁的过程中，一个关键问题是“可喷发的岩浆体是如何形成的，它们会持续多久？”为了回答这个问题，该项目将重点关注阿根廷卡塔马卡目前活跃的Cerro Blanco火山群（CBVC）。在这里，近3万年的三次大爆发记录了一个活跃的破火山口火山的幕式发展。该项目将利用岩浆中生长的矿物的化学成分和年龄，揭示CBVC岩浆的生长、发育和持久性。研究人员将使用最新的方法对火山喷发的单个矿物进行年代测定和地球化学分析。将开发分析和建模这些数据的新方法。该项目有许多更广泛的影响，有利于学科和社会。高级科学团队是国际化和多样化的。这些资深科学家将指导一名来自阿根廷的年轻科学家。一名本科生研究员也将深入参与该项目。该项目的成果将支持当地旅游业，并成为火山科学家未来实地研讨会的重点。该项目将限制岩浆过程和通量，这些岩浆过程和通量聚集并维持了安第斯山脉中央火山区3万年的强烈流纹岩火山活动。本文将对世界范围内与俯冲相关的火山口火山的两个假设进行验证：1)导致CBVC发育演化的岩浆通量是世界范围内典型的弧相关岩浆通量；2) CBVC是幕式复合弧深岩体的地表表现。该项目的第一阶段将利用锆石中的u系列和U-Th/He耦合（锆石双测年或ZDD）来细化CBVC的喷发频率和速度，并描绘CBVC的时空发展。这个框架将被用来探测岩浆的演化、发展和岩浆复合体的现状，直接检验这两个假设。为此，还将收集锆石中的微量元素和o同位素，并将其与熔体化学、流纹岩熔体和锆石热化学模型相结合。这项研究的结果将包括对这些系统的热化学建模的新努力，这将促进对岩浆是如何在喷发前储存在浅层地壳中的理解，以及如何形成历史上发生过的大规模灾难性喷发，因此具有直接的社会意义。这些知识对于岩基如何形成、地壳如何演化以及矿体如何形成也是至关重要的。该项目以国际合作为特色，提供了将年轻火山系统的年龄测定和地球化学联系起来的最新方法。一个由资深科学家组成的多元化团队将指导一名来自阿根廷的早期职业研究人员和本科生研究人员，以确保解决人力资本开发、知识转移和本科生研究经验的更广泛影响。与当地旅游业的合作，以及未来的实地研讨会，都将带来更广泛的影响。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。

Explosive volcanic eruptions affect society from local to global scale. Locally and regionally, society and infrastructure may be devastated. Globally, such eruptions can affect global climate. Historic examples include Tambora 1815 and Pinatubo 1991. These eruptions occur at subduction zones, where Earth’s tectonic plates converge. They also form calderas, where the ground above the magma chamber collapses to produce a big depression. Such eruptions have occurred at a frequency of several per century, so they are of concern to society. A key question in the efforts to understand the potential threat from such caldera volcanoes is “how are eruptible bodies of magma assembled and for how long do they persist?”. To answer this question, the project will focus on the currently active Cerro Blanco Volcanic Complex (CBVC) in Catamarca, Argentina. Here, three major explosive eruptions in the last ~30,000 years record the episodic development of an active caldera volcano. The project will reveal the growth, development, and persistence of magma at the CBVC using the chemistry and age of minerals that grew in the magma. The latest approaches to age dating and geochemistry of individual minerals from the eruptions will be used. New ways of analyzing and modeling these data will be developed. The project has many broader impacts that benefit the discipline and society. The senior science team is international and diverse. These senior scientists will mentor a junior scientist from Argentina. An undergraduate researcher will also be deeply involved in this project. The outcomes of this project will support the local tourism industry and be the focus of a future field workshop for volcano scientists.This project will constrain the magmatic processes and fluxes that have assembled and sustained a 30,000-year locus of intense rhyolitic volcanism in the Central Volcanic Zone of the Andes. Two hypotheses relevant to subduction-related caldera volcanoes worldwide will be tested: 1) The magmatic flux that led to the development and evolution of the CBVC is typical of arc-related magmatic fluxes worldwide; and 2) The CBVC is the surface expression of an episodically built composite arc pluton. The first phase of the project will utilize coupled U-series and U-Th/He in zircon (Zircon Double Dating or ZDD) to refine the eruptive frequency and tempo of the CBVC and delineate the spatiotemporal development of the CBVC. This framework will then be used to probe the magmatic evolution, development, and current state of the magmatic complex, directly testing the two hypotheses. To do this, trace elements and O-isotopes in zircon will also be collected and integrated with melt chemistry, rhyolite-MELTS, and thermochemical modeling of zircon ages. The outcomes of the study will include new efforts in thermochemical modeling of these systems that will advance the understanding of how magma is stored pre-eruption in the shallow crust and builds up to catastrophic eruptions of a scale that have occurred in historic times and are therefore of immediate social relevance. This knowledge is also fundamental to how batholiths are constructed, the earth’s crust evolves, and how ore bodies form. The project features international collaborations that provide access to the newest approaches to link age dating and geochemistry of young volcanic systems. A diverse team of senior scientists will mentor an early career researcher from Argentina and undergraduate researchers to ensure that broader impacts of human capital development, knowledge transfer, and research experience for undergraduates are addressed. Outreach to local tourism efforts, and a future field workshop round out the broader impacts.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.