Assessing changes in the state of a magma storage system over caldera-forming eruption cycles, a case study at Taupo Volcanic Zone, New Zealand

最大规模的火山爆发是罕见事件，但可能代表一场全球性的灾难。较小规模的火山喷发仍可能产生重大（数十亿美元）的经济影响，并可能影响大量人口的生活和生计，即使是在远离火山喷发的地方（例如，2010年冰岛相对较小的火山喷发）。该项目以新西兰陶波火山带（Taupo Volcanic Zone， TVZ）为研究对象，研究一个大型且非常活跃的火山系统，重点是更好地了解地表以下岩浆体的温度和流动性在一次大喷发之前、期间和之后的变化。这项研究将有助于我们了解产生如此大规模喷发的火山（例如，美国黄石火山系统），并将为解释这些火山和其他活火山的实时危害监测提供关键背景。此外，该项目还将包括为一名K-12教师提供研究经验，并制定将广泛传播的新的基于标准的物理、化学和数学课程。这个雄心勃勃的项目将使人们对控制硅质岩浆系统行为的过程，特别是那些导致大型火山口形成喷发的过程有更全面的了解。这将通过将年龄数据与在TVZ喷发岩浆的结晶（斜长石和锆石）和液体（熔融包裹体）部分的成分数据相结合的详细研究来完成。这些数据将为采用两条主要研究路线的新方法提供基础：1)通过将u系列测量得到的斜长石晶体种群的绝对年龄与微量元素扩散模型相结合，约束喷发前岩浆储存的热历史，以约束晶体在给定温度下的最大停留时间；2)通过原位测量原生矿物和副矿物以及熔体包裹体（锆石&amp；#948;18O，锆石&amp；#949;Hf）中的微量元素和同位素组成，定量分析晶体和熔体成分的非均质性；斜长石和熔融包裹体中的铅同位素)，这将提供岩浆系统在储层中跨时间和空间混合程度的测量，以及地幔和地壳源对储层贡献的变化。这种方法的独特之处在于，它可以同时表征这些硅储层的热、成分和物理演化。因此，本研究的结果将广泛适用于其他硅质火山系统，并将在提高我们解释火山监测数据的能力方面迈出重要的一步。大型硅系统代表了全球火山活动的末端成员，通过将本研究结果与其他正在进行的项目的结果联系起来，将开发出控制火山下岩浆储存热条件的更一般的模型。

The largest volcanic eruptions are rare events but can represent a global catastrophe. Smaller eruptions may still have significant (billions of dollars) economic impacts and may affect the lives and livelihoods of large numbers of people, even in places distant from the erupting volcano (e.g., the relatively small eruption in Iceland in 2010). This project focuses on the Taupo Volcanic Zone (TVZ) in New Zealand as a case study of a large and very active volcanic system, and will focus on developing a better understanding of how the temperature and mobility of a magma body below the surface changes before, during, and after a major eruption. This study will contribute to our understanding of the volcanoes that produce such large eruptions (for example, Yellowstone volcanic system in the US), and will provide critical context for interpretation of real-time hazard monitoring at these and other active volcanoes. In addition, the project will include research experience for a K-12 teacher and development of new standard-based physics, chemistry and mathematics curriculum that will be disseminated broadly.This ambitious project will develop a more complete understanding of the processes that govern the behavior of silicic magmatic systems, and, in particular, those that lead to the development of large, caldera-forming eruptions. This will be accomplished by a detailed study coupling age data with compositional data for both crystalline (plagioclase and zircon) and liquid (melt inclusions) parts of the erupted magma at the TVZ. These data will provide the foundation for a novel approach using two primary lines of investigation: 1) Constraints on the thermal history of pre-eruptive magma storage by coupling absolute ages for plagioclase crystal populations derived from U-series measurements with trace element diffusion models to constrain the maximum residence time of crystals at a given temperature; and 2) Quantification of the compositional heterogeneity of crystals and melt components, through in-situ measurements of trace-element and isotopic compositions in primary and accessory minerals and in melt inclusions (δ18O in zircon, εHf in zircon; Pb isotopes in plagioclase and melt inclusions), which will provide a measure of the degree to which the magma system is mixed across time and space within the reservoir as well as variations in the contributions of mantle and crustal sources to this reservoir. The unique strength of this approach is that it will allow simultaneous characterization of the thermal, compositional, and physical evolution of these silicic reservoirs. Therefore, the results of this study will be broadly relevant to other silicic volcanic systems and will represent an important step forward in improving our ability to interpret volcano monitoring data. Large silicic systems represent an end-member for volcanic activity globally, and more general models of the controls on the thermal conditions of magma storage beneath volcanoes will be developed by linking the results of this study with those from other ongoing projects.