Isotope Studies of Mineral Kinetics Accomplishment-Based Renewal

这个项目将探索元素迁移和交换的动力学。最近的技术发展使同位素微量分析的样品比以前可能的小一百万到一百万倍。将研究矿物中化学反应和交换的机制和速率，重点是锆石和钛矿，这两种矿物用于确定地质事件的年龄。这是地质稳定同位素实验室的主要运作拨款，该实验室与威斯康星大学的WiscSIMS实验室密切相关，WiscSIMS实验室是一个稳定同位素地球化学国家设施。更广泛的影响包括稳定同位素地球化学的新应用，公共教育，以及最先进的分析技术在本科到博士后水平的培训。该基金将资助两名研究生，并资助另外两名学生和一名博士后在他们的教育。50多年来，利用大块矿物性质热力学的化学平衡范式一直主导着岩石如何形成的研究，并为认识地球带来了巨大进步。同时，矿物晶界和交换动力学的理论和实验研究表明了体积平衡假设的局限性，实际岩石中稳定同位素交换的微米尺度研究受到分析限制的阻碍。该项目将利用两种仪器的综合能力来克服这些限制：二次离子质谱（SIMS）和原子探针断层扫描（APT）。SIMS从1-20微米直径的斑点测量同位素比率和微量元素，具有出色的准确度和精度。APT将为理解元素和同位素分布提供独特的信息；没有其他技术提供空间分辨质谱和单原子尺度的三维映射。当与岩石学观察（可见光和电子显微镜）和低千伏电子探针显微分析相结合时，这些新技术有望改变对晶界和纳米域的交换率和反应动力学的理解。

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.