Diffusion in Garnet: Extracting Rates From Natural Occurrences

利用电子探针和激光烧蚀电感耦合质谱分析了来自德克萨斯州和拉布拉多的部分吸收石榴石晶体边缘的成分梯度。这些链扩散曲线起源的计算机模拟将用于限制主要元素（Mg, Fe, Mn, Ca）和微量元素（例如，Y, Yb, Dy, Sm, Ce, Nd）的晶内扩散的相对和绝对速率。该项目将扩大和丰富现有的石榴石扩散数据集，将其扩展到与地壳变质过程相关的温度和压力，将其扩展到更多感兴趣的元素，并将其扩展到更广泛的地质上重要的石榴石成分。预计这些新数据将应用于地温压学、地质年代学、变质地体的加热和冷却历史评估以及构造隆起速率的量化等领域。在该项目中，本科生和研究生将获得电子探针微分析、激光烧蚀技术、四轴质谱和高分辨率x射线计算机断层扫描等最先进的分析技能。

Carlson EAR-0229529Compositional gradients at the rims of partially resorbed garnet crystals from Texas and Labrador will be analyzed by electron microprobe and laser-ablation inductively coupled mass spectrometry. Computer simulations of the origin of these stranded diffusion profiles will be used to place limits on the relative and absolute rates of intracrystalline diffusion of both major elements (Mg, Fe, Mn, Ca) and trace elements (e.g., Y, Yb, Dy, Sm, Ce, Nd). The project will enlarge and enrich the existing dataset on diffusion in garnet, extending it to the temperatures and pressures relevant to crustal metamorphic processes, expanding it to a greater number of elements of interest, and broadening it to encompass a wider range of geologically important garnet compositions. Applications of the new data are foreseen in the areas of geothermobarometry, geochronometry, assessment of heating and cooling histories in metamorphic terranes, and quantification of rates of tectonic uplift, among others. During the project, undergraduate and graduate students en route to professional scientific careers will acquire state-of-the-art analytical skills in electron-probe microanalysis, laser-ablation technology and quadrapole mass spectrometry, and high-resolution X-ray computed tomography.