Investigation of Secondary Water in Volcanic Glass and its Isotopic Signatures

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Glass formed by quick quenching of magma from erupting volcanoes may inform us about climatologic conditions because these materials react with the atmosphere when exposed to the environment. The reaction of water with volcanic glass creates a hydration zone that reflects the meteoric conditions at the time. These zones can be measured with hydrogen and oxygen stable isotopes that can then be used to infer the environmental conditions at the time of the eruption. This research will constrain geological mechanisms of hydration of natural glass with a combination of experiments, theoretical computations, and natural observations. Results of this type of research will be applicable to questions related to the stability of hazardous waste disposal, the alteration of obsidian and chert artifacts in archeological environments, and the formation of perlite that is an important natural material used in industry. Knowledge of these geological processes can also inform us on how fumarole mounds were formed in the Crater Lake and Katmai National Parks, and how hydration alteration of glass can be imaged with remote, and rover-based sensing on Earth, Mars and other planets that have water in their atmospheres. This project will promote synergy and collaboration among the newly created Volcanology cluster hire program at the University of Oregon and will promote international collaboration. Funding will support graduate and undergraduate students, and analytical infrastructure of the stable isotope lab at the University of Oregon.Newly available continuous flow mass spectrometric, and microbeam methods now permit multi-method isotopic investigation of volcanic glass with relative ease for the first time. The experimental study will investigate hydrogen and triple oxygen isotopic fractionation factors for silicic glasses and water from ambient to hydrothermal (25 to 250 C) temperatures. The investigator will image hydration profiles in experimental products with NanoSIMS and FTIR targeting water and D/H exchange profiles and model them to derive fractionation and diffusion parameters. With collaborators, he will perform ab initio equilibrium isotopic and numerical kinetic isotopes fractionation of glass and analogous zeolite phases upon hydration and exchange with water. The newly developed hydrogen isotope methods in combination with triple oxygen isotope parameters in glass will create predictive criteria for hydrating meteoric waters (glacial or interglacial). Using experimentally-determined hydration and isotopic trends from the experiments and literature data, the model will predict secondary hydration, alteration, and isotopic trends across the deposit during its cooling, with percolative and channelized water transport as is observed in gas escape pipes. The above results are relevant for understanding water-glass interaction after ignimbrite and lava emplacement, and for paleoclimate research, as silicic glass hydrates during cooling within months to 10s of years upon emplacement, providing instantaneous snapshots of meteoric water isotopic values. Isotopic parameters in rapidly hydrated thick-walled perlites and fumarole escape pipes are better targets for preservation of climatic signal than thin-walled ash that hydrates over 1000s of years and averages out century to millennia-scale signals. In application to nature, the proposal will explain the origin of Crater Lake Pinnacles and deposits at the Valley of 10,000 Smokes by specifically targeting kinetics and the duration of water-rock interactions, allowing the recognition of glacial vs. interglacial hydration.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.