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

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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.