NSFGEO-NERC: Collaborative Research: Linking geophysics and volcanic gas measurements to constrain the transcrustal magmatic system at the Altiplano-Puna Deformation Anomaly

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The path that magma takes through the crust is not well understood -- where is magma stored and under what conditions will it erupt? While this question is of fundamental scientific interest, it is also directly related to understanding the hazard posed by volcanic systems that are showing signs of activity and unrest. This project seeks to understand the cause of unrest and the architecture of the magma storage system within the central Andes, home to the world's largest geophysically imaged zone of silicic partial melt, the Altiplano-Puna Magma (or Mush) Body (APMB). This project involves scientists in the USA, United Kingdom, and Bolivia to collect new field measurements (gravity, ground deformation, seismic, gas flux and composition) at Uturuncu volcano, Bolivia and develop numerical models of the volcano motivated by the new data. In particular, the new data will add to the limited understand of the background activity at restless volcanoes that is necessary to better assess the hazard of future volcanic unrest -- what is normal activity and what should cause concern?There is a new emerging paradigm of a transcrustal magmatic system (TCMS) where magma storage and differentiation occurs at several locations throughout the entire crustal column. This conceptual revolution is being driven by petrological, geochronological, and geochemical studies of magma storage conditions that show (1) many large eruptions tap multiple melt sources, (2) large melt bodies are probably transient features, (3) crystals carried by the transporting melt have been stored at a range of pressures and temperatures. A key location to assess and refine models of currently active TCMS is at the APMB, where a large ground deformation pattern 150 km in diameter lasting several decades has been observed centered on Uturuncu volcano, Bolivia. By collecting and analyzing new interdisciplinary field measurements (gravity, ground deformation, seismic, gas flux and composition) and developing 3D numerical models, this proposal will answer several outstanding questions about the nature of TCMS at the APMB: 1. What is the cause of deformation in the midcrust at the APMB: a magmatic diapir, cyclic up and down movements from magma mush reorganization involving magma and/or volatiles, or something else? 2. What is the nature of a shallow-seated conductivity anomaly -- to what extent is it partial melt, a hydrothermal brine reservoir, or a mature ore body? 3. What is the flux of volatiles through the TCMS? 4. How important is crustal anisotropy in the interpretation of the subsurface magma plumbing architecture?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.