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可能会发生变化，因为同一元素的不同同位素具有略有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用途的基本过程，包括发展同位素分离方法、同位素年龄测定中的同位素比值校正、原子尺度扩散过程的检验以及成岩历史和速率的推断。这个项目将研究具有天然同位素组成的熔融玄武岩在多组分扩散过程中的同位素分馏。具体地说，将评估岩石中三种主要元素K、钛和镁的扩散同位素分馏。该项目将为研究生提供一个研究机会。将开发新的方法和分析方案，这将对许多其他研究人员有用。通过突破现有SIMS仪器的极限来解决淬火玻璃中的同位素比值变化问题，将测量现有特性良好的实验装药中K、Ti和Mg的同位素比值。即将获得的同位素数据最终将使研究人员能够在基本的分子和离子水平上了解扩散机制。该项目还将推进同位素比率测量的SIMS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。这项工作将有助于从根本上理解镁铁质硅酸盐熔体中的扩散和同位素分馏。此外，这些结果还可用于了解岩浆混合和矿物生长，以及推断岩石的冷却时间尺度。研究生将接受培训并参加科学会议。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.