RUI: Tracking magma accumulation and evolution in the Andean Central Volcanic Zone

大陆弧火山代表了全球构造中最重要和最基本的现象之一的戏剧性表面表现：海洋板块俯冲到更浮力的大陆板块之下，导致地壳物质循环进入对流地幔，部分熔融，并产生原始玄武岩。此外，在穿过厚厚的大陆地壳时，俯冲带岩浆可能会对地壳岩石产生实质性的分异和熔融，从而导致地球上火成岩岩性的巨大多样性。大陆弧上的火山爆发可能会对全球造成毁灭性的影响，其爆炸性应归因于储存在地壳中的岩浆的成分和体积。大型岩浆储存系统的开发在很大程度上仍不为人所知，在火山学家中也存在很大争议。这个项目将研究累积的岩浆是如何储存和随时间演化的。研究人员试图描述智利和玻利维亚安第斯中央火山带火山下现代岩浆室中岩浆储存的过程和时间尺度。越来越多的证据表明，最大和最具爆炸性的喷发所需的大规模岩浆储集层，如安第斯中部阿尔蒂普诺-普纳火山杂岩中的喷发，是在炎热的地壳环境中迅速建立的。在这个为期3年的项目中，研究生和本科生将通过与一个国际地质学家团队的合作来扩展他们的研究技能，这些地质学家试图了解导致火山喷发的地壳融化和岩浆储存的动力学。该项目强调实验室、实地和协作设施中的分析方法培训。该项目将侧重于智利和玻利维亚安第斯中央火山带(奥坎基尔查、奥拉古厄、乌图伦库、圣佩德罗-林佐尔、利坎卡布尔、拉祖夫雷和拉斯卡尔)复合火山复合体中的年轻火山岩，这些火山岩在空间和时间上联系密切，以研究导致岩浆积累和最终火山喷发的过程和时间尺度。这个项目的主要目的是调查累积的岩浆是如何储存和随时间演化的。这将通过确定现代岩浆室中岩浆分异的过程和时间尺度以及确定区域岩浆体对安第斯山脉中部火山的影响来实现。来自每个中心的新的和现有的样品将被用来解决三个基本问题：1)岩浆在各个活跃的中心停留多久；2)岩浆源和部分熔融过程是否随着火山产品的地球化学演化而发生系统的变化；以及3)区域尺度的上地壳岩浆储集层参与控制喷发成分的证据是什么？建议的研究将利用定向野外采样、全岩地球化学、40Ar/39Ar年代学、高精度锆石年代学/地球化学和斜长石中的微量元素扩散来解决这些问题。最终，这项研究中产生的数据集将提供对形成大陆地壳的岩浆的生成和多样性的洞察。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Continental arc volcanoes represent a dramatic surface expression of one of the most significant and fundamental phenomena in global tectonics: the subduction of an oceanic plate beneath a more buoyant continental plate resulting in recycling of crustal material into the convecting mantle, partial melting, and primary basalt production. Moreover, during passage through thick continental crust, subduction zone magmas may substantially differentiate and melt crustal rocks giving rise to the great diversity of igneous lithologies characteristic of earth. Explosive volcanic eruptions at continental arc can have devastating global effects and owe their explosiveness to the composition and volume of magma stored in the crust. The development of large magma storage systems remains largely unknown and very controversial among volcanologists. This project will investigate how accumulated magma is stored and evolves over time. The investigators seek to characterize the processes and timescales of magma storage in the modern magma chambers beneath volcanoes in the Andean Central Volcanic Zone of Chile and Bolivia. Growing evidence suggests that the massive magmatic reservoirs required for largest and most explosive eruptions, such as those in the Central Andean Altiplano-Puna Volcanic Complex, are built rapidly in hot crustal environment. Over the 3-year project, graduate and undergraduate students will expand their research skills by working collaboratively with an international team of geologists seeking to understand the dynamics of crustal melting and magma storage leading to volcanic eruptions. The project emphasizes training in analytical methods in the lab, in the field, and at collaborating facilities.This project will focus on young volcanic rocks from composite volcano complexes in the Andean Central Volcanic Zone of Chile and Bolivia (Aucanquilcha, Ollagüe, Uturuncu, San Pedro-Linzor, Licancabur, Lazufre and Lascar) linked closely in space and time, to address the processes and timescales leading to the buildup of magma and eventual volcanic eruption. The primary intent of this project is to investigate how accumulated magma is stored and evolves over time. This will be accomplished by characterizing the processes and timescales of magma differentiation in the modern magma chambers and determining the influence of regional magma bodies on Central Andes volcanoes. New and existing samples from each center will be used to address three basic questions: 1) how long does magma reside at active individual centers; 2) do magmatic sources and partial melting processes vary systematically with the geochemical evolution of volcanic products; and 3) what is the evidence for involvement regional-scale upper crustal magma reservoirs in controlling eruptive composition? The proposed research will use targeted field sampling, whole rock geochemistry, 40Ar/39Ar geochronology, high precision zircon geochronology/geochemistry and trace element diffusion in plagioclase to address these questions. Ultimately, the dataset produced in this study will provide insight into the generation and diversity of magmas that form continental crust.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.