Collaborative Research: Structure and properties of geofluids and their impact on fluid migration in subduction zones

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Magmatism plays a vital role in transporting matter and energy from the Earth’s deep interior to the surface. While some eruptions are explosive, others erupt without major explosive behavior, leading to different natural hazards for each eruptive style. These distinct eruption styles are controlled by the fundamental physical properties of magma, particularly viscosity, and density. The viscosity of magma is highly dependent on the atomic-scale structure of the magma, influenced by magma composition, temperature, pressure, and the presence of dissolved gasses such as water vapor. In this study, the researchers aim to obtain fundamental physical constraints on the structure and viscosity of magma at conditions relevant to the Earth’s interior. We will combine the experimentally derived physical properties of magma and fluids with numerical simulations to predict how magmas migrate from the Earth’s subducting plates. It is the migration of this material that ultimately leads to eruptions at the surface, but the complex role of viscosity in magma transport makes it difficult to trace material from its source in the interior to the surface. The project will provide training for the next generation of Earth Scientists at various stages of their career, including high school, undergraduate, and graduate students, as well as post-doctoral scholars. Although extensive research has been done to constrain the elastic and transport properties of fluids and melts at conditions relevant to the Earth’s interior, the combined effects of pressure, temperature, and dissolved water remain poorly constrained at the conditions of the upper mantle where these melts are produced. This research will couple lab- and synchrotron-based experimental data to pressures up to 20 GPa with first-principles molecular dynamics (FPMD) simulations, with the objective to determine the local melt structure, and fluid and melt viscosity to high pressures and temperatures. This work will quantify the structure and properties of aqueous fluids with dissolved albite, in addition to albite and basaltic melts with and without water. The results will provide insight into how pressure, temperature, and composition affect the structure and viscosity of polymerized aluminosilicate melts at mid-mantle depths and illuminate the causes of observed pressure anomalies on viscosity. The resulting viscosities will be integrated into two-phase flow models in the slab-arc system and the upwelling region above the mantle transition zone to assess the pathways of melt migrations through state-of-the-art geodynamical models. These models will assess how the pattern of fluid migration changes with slab age and subduction rate, slab thermal structure, and the distribution and volume of fluid sources in the subducting slab. The resulting work will assess the impact of fluid volumes due to melting and whether melting alone is sufficient to focus melts into a narrow region beneath volcanic regions.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.