Collaborative Research: RUI: Diffusion studies in baddeleyite and zircon

矿物锆石(ZrSiO4)和斜锆石(ZrO2)虽然只以低浓度存在于大多数岩石中，但在地质计时学(测量岩石、陨石和地质事件的年龄)中是重要的阶段。它们含有可用作地球化学指示剂的痕量和次要元素。尤其是锆石，是一种非常坚固的矿物颗粒，因为它们可以在许多类型的地质事件中幸存下来，是地球上已知的最古老的材料之一。他们保存了有关44亿年前发生的地质过程的信息。了解这些矿物中关键元素的扩散(原子迁移率)行为，对我们如何解释测得的年龄、岩石的化学特征和古代地质事件提供了重大限制。关于几种化学元素在锆石中的扩散已经有了广泛的研究，即使有些元素还没有得到充分的研究。相比之下，完全缺乏斜斜晶石的扩散数据，这可以提供与锆石分析所获得的信息相补充的信息。了解这些矿物中的扩散对于解释广泛的地质计时数据以及评估和解释在地质时间框架内保留在这些矿物中的化学和同位素特征至关重要。这项工作的主要更广泛影响将是重要数据的贡献，这些数据可供广泛的科学家在不同但相关的领域使用。该项目还将为物理、工程和地球科学专业的本科生以及来自贫困社区的高中生提供教育体验。拟议的实验建立在一系列工作的基础上，测量各种元素在辅助矿物(岩石中通常丰度较小的矿物，但包含地质计时仪或地球化学示踪剂等重要元素)中的扩散，以获得这些关键矿物的更完整的地球化学图。这项工作还继续改进和应用基于加速器的离子束技术(卢瑟福背散射光谱和核反应分析)在扩散研究中，利用这些分析方法的卓越深度分辨率来获取这些材料中许多物种的缓慢扩散特性。随着微量分析技术越来越多地应用于分析自然样品并获得精细的化学和同位素变化，扩散数据成为解释地质事件的时间以及评估过去的化学环境和热史的关键参数。这些测量将为解释斜晶石的同位素年龄和热历史提供关键信息，斜晶石是一种感兴趣的矿物，但目前几乎没有扩散数据。五价阳离子在锆石中扩散的测量将提供有关元素抗化学蚀变的信息，这些元素可能被用作地球化学示踪剂，为价阳离子扩散的替代机制和电荷平衡提供洞察。Xe的扩散结果可能对更好地解释Xe同位素体系和地球和月球样品中的惰性气体行为，以及理解早期地球和太阳系的历史具有重要意义。氧化锆还可以用作耐火材料和光学材料，因此更好地了解它的性质可能具有技术意义。这项工作的更广泛影响将是重要数据的贡献，可供广泛的科学家在地球科学中不同但相关的领域使用，包括热年代学、地质年代学和早期地球和太阳系研究。该项目将让本科生参与研究，提供制备样品、晶体合成、进行实验、使用各种分析方法以及分析和解释数据以及在研究会议上发表演讲的经验。该项目还将支持旨在向当地高中生介绍科学研究方法和地球科学的社区外展活动。该项目由岩石学和地球化学部和地球科学部联合资助，以支持各种机构类型提高研究能力、能力和基础设施的项目，正如地球观测组织拥抱DCL所概述的那样。该奖项反映了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。

The minerals zircon (ZrSiO4) and baddeleyite (ZrO2), although present only in low concentrations in most rocks, are important phases in geochronometry (measuring ages of rocks, meteorites, and geologic events). They incorporate trace and minor elements useful as geochemical indicators. Zircons in particular are very robust mineral grains and, since they can survive many types of geological events, are some of the oldest known materials on Earth. They have preserved information about geological processes that were occurring up to 4.4 billion years ago. Understanding the diffusion (mobility of atoms) behavior of key elements inside these minerals provides major constraints on how we interpret the measured ages, and chemical signatures of rocks and ancient geological events. There has been extensive study of diffusion of several chemical elements in zircon, even if some elements have been understudied. In contrast, there is a lack of diffusion data entirely for baddeleyite, which can yield complementary information to that gained from zircon analysis. Understanding diffusion in these minerals is essential for interpreting a wide range of geochronometric data, and evaluating and interpreting the chemical and isotopic signatures retained in these minerals over geologic timeframes. The main broader impacts of this work will be a contribution of important data that can be used by a wide range of scientists in diverse, but related, fields. The project will also provide an educational experience for undergraduate students in physics, engineering, and geosciences, as well as high school students from underserved communities. The proposed experiments build on a body of work measuring diffusion of a variety of elements in accessory minerals (minerals in generally minor abundance in rocks, but which incorporate elements important as geochronometers or geochemical tracers), to obtain a more complete geochemical picture of these critical minerals. The work also continues the refinement and application of accelerator-based ion beam techniques (Rutherford Backscattering Spectroscopy and Nuclear Reaction Analysis) in diffusion studies, exploiting the superior depth resolution of these analytical methods to access the slow diffusivities characteristic of many species in these materials. With the increasing application of microanalytical techniques to analyze natural samples and access fine-scale chemical and isotopic variations, diffusion data are a critical parameter in interpreting timing of geologic events, and evaluation of past chemical environments and thermal histories. These measurements will yield critical information for interpreting isotopic ages and thermal histories for baddeleyite, a mineral of interest but for which little diffusion data currently exist. The measurements of pentavalent cation diffusion in zircon will provide information about the resistance to chemical alteration of elements potentially useful as geochemical tracers, provide insight into substitutional mechanisms and charge balance for diffusion of altervalent cations. The Xe diffusion results may have implications for better interpreting Xe isotope systematics and noble gas behaviors in terrestrial and lunar samples, and understanding histories of the early Earth and Solar System. Zirconia also has utility as a refractory and optical material, so better understanding of its properties may have technological implications. The broader impacts of this work will be as a contribution of important data that can be used by a wide range of scientists in diverse, but related, fields in the geosciences, including thermochronology, geochronology, and studies of the early Earth and Solar System. The project will involve undergraduate students in research, providing experience in preparing samples, crystal synthesis, conducting experiments, using various analytical methods, and analyzing and interpreting data and presenting at research conferences. The project will also support a community outreach effort aimed at introducing local high school students to scientific research methods and Earth science.This project is jointly funded by Petrology & Geochemistry and Division of Earth Sciences to support projects that increase research capabilities, capacity and infrastructure at a wide variety of institution types, as outlined in the GEO EMBRACE DCL.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.