Diffusion in Garnet: Extracting Rates From Natural Occurrences

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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.