Collaborative Research: Residual Stress Preserved in Crystals from Volcanic Eruptions

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Volcanic eruptions transport magma from reservoirs deep underground to the surface through conduits. Because volcanic processes occur underground, or are very dangerous to approach, many key aspects of volcanic eruptions are difficult to study with direct observations. Here, a new technology called synchrotron X-ray micro diffraction (microXRD) will be used to document deformation preserved in crystals that were transported within volcanic eruptions. The microXRD technique measures the amount of strain and preserved stress in the crystal lattice of those crystals. Volcanic stresses are important because they control eruption processes, including magma movement and explosivity. The first step to interpreting residual stress is to identify the specific processes that strain volcanic crystals. To this end, volcanic simulation experiments will be performed to deform crystals. MicroXRD will be used to analyze the experimental products and then compare results with natural crystals. This set of experiments and measurements will address the "How" and "Why" of volcanic eruptions. The standards and techniques developed in this project will enable application of microXRD to other disciplines, including Tectonics, Meteoritics, and Materials Science. The forces that act on magmas control volcanic processes. Consequently, crystals from volcanic eruptions are strained in the magma chamber, conduit, and during emplacement. Synchrotron X-ray micro diffraction (microXRD) will be used to quantify the magnitude of those strains by analyzing crystal lattice deformation with submicron spatial resolution on a suite of quartz, magnetite, and zircon crystals from the Long Valley and Yellowstone calderas. Measuring the magnitude of strains and using microstructure maps across crystals will reveal how strain is produced and preserved in crystals. Next, the preserved strains will be translated to causal stresses using the elastic constants of the mineral and Hooke's law. The goal is to quantify volcanic stresses in different volcanic environments and assess the forces and the time scales over which those forces act. MicroXRD has exceptional potential as an emerging technology in the geological sciences, but there is limited physical and theoretical infrastructure to interpret datasets. For this reason, high-temperature experiments will be performed to simulate stresses in volcanic environments using unstrained synthetic crystals, and assess the preservation of stress in strained natural crystals. Experimental products will be analyzed by microXRD and used to identify and/or eliminate sources of deformation.