Diffusion in Garnet: Extracting Rates From Natural Occurrences

卡尔森EAR-0229529将用电子探针和激光烧蚀电感耦合质谱仪分析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。将使用计算机模拟这些链状扩散轮廓的来源，以限制主要元素(镁、铁、锰、钙)和痕量元素(例如Y、Yb、Dy、Sm、Ce、Nd)在晶内扩散的相对和绝对速率。该项目将扩大和丰富关于石榴石中扩散的现有数据集，将其扩展到与地壳变质过程有关的温度和压力，将其扩展到更多感兴趣的元素，并将其扩大到包括更广泛的具有重要地质意义的石榴石成分。预计新数据将在地热气压测量、地质计时、变质地体加热和冷却历史的评估以及构造抬升速率的量化等领域得到应用。在该项目期间，走向专业科学职业生涯的本科生和研究生将获得最先进的分析技能，包括电子探针微分析、激光烧蚀技术和四极杆质谱仪，以及高分辨率X射线计算机断层扫描。

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.