Isotope Studies of Mineral Kinetics Accomplishment-Based Renewal

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This project will explore the kinetics of element mobility and exchange. Recent technological developments allow isotopic microanalysis of samples a million to a million-million times smaller than previously possible. The mechanisms and rates of chemical reaction and exchange in minerals will be studied with emphasis on zircon and titanite, minerals used to determine the age of geological events. This is the main operating grant of the Geology Stable Isotope Laboratory, which is closely linked to the WiscSIMS Lab at UW, a National Facility for Stable Isotope Geochemistry. The broader impacts include new applications of stable isotope geochemistry, public education, and training at the undergraduate to post-doc level in state-of-the-art analytical techniques. This grant will support two graduate students, and aid two other students plus one post-doctoral fellow in their educations. The paradigm of chemical equilibrium employing thermodynamics of bulk mineral properties has dominated the study of how rocks form for over 50 years and brought immense progress for understanding the Earth. At the same time, theoretical and experimental studies of mineral grain boundaries and exchange kinetics have demonstrated limitations of the bulk-equilibrium assumption and micron-scale investigations of stable isotope exchange in real rocks have been thwarted by analytical limitations. This project will exploit the combined capabilities two instruments that overcome these limitations: secondary ion mass spectrometry (SIMS) and atom-probe tomography (APT). SIMS measures isotope ratios and trace elements from 1-20 micron diameter spots with excellent accuracy and precision. APT will provide unique information for understanding element and isotope distribution; no other technique provides spatially resolved mass spectrometry and 3-dimension mapping at single-atom scale. When used in context with petrographic observation (visible and electron microscopy) and low-kV electron probe microanalysis, these new techniques promise transformative understanding of exchange rates and reaction kinetics in grain boundaries and nano-domains.