Geochemical Insights Into the Post-Caldera Architecture of the Yellowstone Magma Reservoir

对黄石岩浆库火山口后建筑的地球化学见解

• 批准号: 2204816
• 负责人: Kari Cooper
• 金额: $ 56.24万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2204816&HistoricalAwards=false
• 关键词: Geochemical; Insights; Into; Post; Caldera

Volcanic systems such as Yellowstone in Wyoming produce very large, highly explosive eruptions that form immense craters called calderas. The volcanic system at Yellowstone has had three of these caldera-forming eruptions over the past two million years. In between these very large eruptions the system has also produced many smaller eruptions that were less explosive, which fed large lava flows that partially filled the caldera. As a result, the potential hazards and destructiveness of an eruption at volcanoes such as Yellowstone can vary widely, ranging from nation-wide or even global effects to more local hazards. An open question in volcano science is what factors control whether a volcano produces a very large explosive eruption or a smaller lava flow in a particular eruption. This probably depends partly on how the “plumbing system” beneath volcanoes changes over time, and whether large bodies of mostly-liquid magma are present continuously, whether they build up slowly over long periods of time, or whether they are only present just before an eruption. For example, does generating a very large eruption require a longer time to build a big pool of magma? Does it require more magma bodies to be present than a smaller eruption, or are there the same number of magma bodies present at all times but more of them get triggered to produce a very large eruption? In this project researchers will use chemical “fingerprints” of different magma bodies to identify how many different magma bodies have been tapped in the most recent series of smaller eruptions at Yellowstone, and will compare this to the number of magma bodies that have been identified as part of the most recent caldera-forming eruption to help answer these questions. Understanding how different kinds of eruptions are produced will contribute to volcanic hazard forecasting and risk management. The project will also train graduate and undergraduate students, contributing to the scientific workforce, and public outreach about the results will help contribute to scientific understanding for the general public.Large silicic systems produce a wide range of eruption styles and eruptive hazards, but the connections between the architecture of the magma storage region and the type of eruption produced are not well understood. For example, does a caldera-forming eruption require a different distribution of melts within the shallow reservoir, and/or a different triggering mechanism, than a smaller eruption? As a contribution to answering these broad questions, this team proposes to compare the architecture of the magma system during intra-caldera eruptions to existing data for caldera-forming eruptions at Yellowstone Caldera, Wyoming. New high-precision 40Ar/39Ar dating of the most recent intracaldera eruptions at Yellowstone (the Central Plateau Member, CPM) shows that they were erupted in five episodes, each of which spanned at most 1-2 kyr. This provides an opportunity to examine the number and distribution of magma bodies during each of five snapshots of the magma system, and to compare this with published work on the Yellowstone caldera-forming eruptions. They will investigate compositional diversity recorded in sanidine and zircon crystals both within and between individual eruptions and eruptive episodes using 238U-230Th age data coupled with geochemical data for both sanidine and zircon. Based on previous work, the sanidine and zircon surface compositional data will provide insights into the number of distinct magma bodies present during the period immediately prior to CPM eruptive episodes, as well as constraining the time scale of assembly and storage of different magma bodies prior to eruption. In contrast, zircon interiors are typically older with ages spanning 10s of kyr prior to eruption, which will provide a measure of compositional diversity present on a longer time scale, between eruptive episodes. The team will test the hypothesis that the basic architecture of the magma reservoir consists of multiple compositionally distinct magma bodies within a more heterogeneous crystal mush, and that the state of the system is similar before CFE and recent intracaldera eruptions. The data collected will also allow them to assess whether there are systematic changes in the average composition of erupted crystals over time, which may reflect secular variations in the proportions of mantle-derived and crustal-derived melts contributing to the system. Synthesizing their new data with data for Yellowstone CFE and data for other silicic systems will provide additional insights into the development and evolution of large silicic magma reservoirs. Broader impacts will include outreach by the PI to increase scientific literacy and public engagement, training and mentoring of diverse graduate and undergraduate students, strengthening partnerships between academia and the USGS, and contributing information that will be used to inform public policy and volcanic hazard mitigation.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.

怀俄明州黄石等火山系统会产生非常大的高度爆炸性喷发，形成了巨大的陨石坑。在过去的200万年中，黄石石的火山系统在这些火山口爆发中有三个。在这些非常大的喷发之间，该系统还产生了许多较小的爆发，这些喷发爆发较少，这些喷发喂养了部分填充火山口的大型熔岩流。结果，火山（例如黄石公园）喷发的潜在危害和破坏性可能会有所不同，范围从全国甚至全球影响到更多的局部危害。火山科学中的一个空旷的问题是，哪些因素控制着火山是在特定喷发中产生非常大的爆炸性喷发还是较小的熔岩流。这可能部分取决于火山下的“管道系统”如何随着时间的推移而变化，以及是否连续存在大部分液体岩浆的大物体，它们是否长时间缓慢积聚，还是仅在喷发前就存在。例如，产生非常大的喷发是否需要更长的时间来建造大量的岩浆？是否需要比较小的喷发需要更多的岩浆体，或者始终存在相同数量的岩浆体，但其中更多的岩浆体被触发以产生非常大的喷发？在这个项目中，研究人员将使用不同岩浆物体的化学“指纹”来确定在黄石的最新较小喷发中挖掘了多少种不同的岩浆体，并将将其与已确定为最近的Caldera-oforming爆发的一部分的岩浆物体进行比较，以帮助回答这些问题。了解如何产生各种喷发将有助于火山危害预测和风险管理。该项目还将培训研究生和本科生，为科学劳动力做出贡献，公众对结果有助于对公众的科学理解，从而产生广泛的喷发风格和喷发危险，但是在岩浆存储区域的建筑与所产生的喷发类型的类型之间的建筑之间的联系不知道。例如，与较小的喷发相比，对浅层储层中的熔体喷发和/或不同的触发机制需要不同的熔体分布吗？作为回答这些广泛问题的贡献，该团队提出的建议将岩浆系统的架构与卡尔德拉爆发期间的岩浆体系与怀俄明州黄石火山口爆发的现有数据进行比较。新的高精度40AR/39AR在黄石（中央高原成员，CPM）的最新阿尔德尔氏爆爆发表明，它们在五集中爆发，每集最多1-2 kyr。这提供了一个机会，可以在岩浆系统的五个快照中检查岩浆体的数量和分布，并将其与关于黄石火山口爆发的已发表作品进行比较。他们将使用238U-230年龄的数据以及Sanidine和锆石的地球化学数据结合的238U-230年龄数据，研究单个喷发和喷发发作之间和爆发性发作之间记录的复合多样性。基于先前的工作，Sanidine和锆石表面组成数据将提供有关CPM喷发发作之前此期间存在的不同岩浆物体数量的见解，并限制了爆发前的组装和存储的时间尺度和存储的时间尺度。相比之下，锆石内饰通常在喷发前跨越10 s的年龄，这将提供爆发性发作之间的较长时间尺度上存在的复合多样性的度量。该团队将检验以下假设：岩浆晶状体的基本体系结构由更异质的晶体肌肉中的多个合成的岩浆体组成，并且系统的状态在CFE和最近的层爆发之前相似。收集到的数据还将允许他们评估爆发晶体的平均组成随着时间的流逝是否存在系统的变化，这可能反映了对地幔衍生和地壳衍生的熔体比例的安全变化，从而有助于系统。将其新数据与黄石CFE的数据和其他硅系统的数据合成，将为大型硅岩浆储量的开发和演变提供更多见解。更广泛的影响将包括PI的宣传，以提高科学素养和公众参与度，对潜水员毕业生和本科生的培训和心理，加强了学术界与USGS之间的伙伴关系，以及将贡献信息，这些信息将用于公共政策和火山危害的措施，这些奖项通过评估NSF的稳定范围来依据，这反映了NSF的稳定范围。 标准。