Isotope Fractionation During Multicomponent Diffusion in Molten Basalts

自然界中的同位素比率在平衡或动力学过程中会发生变化，因为同一元素的不同同位素具有略微不同的物理和化学性质。扩散过程中的同位素分馏是一个具有多种应用的基本过程，包括发展同位素分离方法，校正同位素年龄测定中的同位素比率，检查原子尺度的扩散过程，以及推断历史和岩石形成速度。本项目将研究具有天然同位素组成的熔融玄武岩多组分扩散过程中的同位素分馏。具体来说，将对岩石中三种主要元素K、Ti和Mg的扩散同位素分馏进行评估。这个项目将为研究生提供一个研究机会。新的方法和分析方案将被开发出来，这将对许多其他研究人员有用。现有实验电荷中K、Ti和Mg的同位素比值将通过突破现有SIMS仪器的极限来测量，以解决淬火玻璃中同位素比值的变化。获得的同位素数据最终将使研究人员能够了解基本分子和离子水平上的扩散机制。该项目还将推进SIMS同位素比值测量技术，并将应用于岩浆混合以及矿物溶解和生长的自然过程中的同位素分馏。这项工作将有助于对镁基硅酸盐熔体中扩散和同位素分馏的基本认识。此外，该结果还可用于了解岩浆混合和矿物生长，并推断岩石冷却的时间尺度。研究生将接受培训并参加科学会议。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Isotope ratios in nature can change during equilibrium or kinetic processes because different isotopes of the same element have slightly different physical and chemical properties. Isotope fractionation during diffusion is a fundamental process with multiple applications, including development of methods for separation of isotopes, correction for isotope ratios in isotope age determination, examination of atomic scale processes of diffusion, and inference of history and rate of rock formation. This project will investigate isotope fractionation during multicomponent diffusion in molten basalts with natural isotope compositions. Specifically, diffusive isotope fractionation of three major elements in rocks, K, Ti, and Mg, will be evaluated. The project will provide a research opportunity for a graduate student. New methodologies and analytical protocols will be developed that will be useful to many other researchers. Isotope ratios of K, Ti ad Mg in existing well-characterized experimental charges will be measured by pushing the limits of current SIMS instruments to resolve the isotope ratio variation in the quenched glass. The isotope data to be acquired will ultimately enable researchers to understand diffusion mechanisms at the fundamental molecular and ionic level. The project will also advance the SIMS technique for isotope ratio measurements and will have applications to isotope fractionation during natural processes of magma mixing as well as mineral dissolution and growth. This work will contribute to the fundamental understanding of diffusion and isotope fractionation in mafic silicate melts. In addition, the results can be applied to understand magma mixing and mineral growth, and to infer cooling time scales of rocks. Graduate students will be trained and will attend scientific meetings.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.