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

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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.