Quantification of element transport processes in metamorphic rocks - simulating garnet porphyroblast growth in a three dimensional composition-space-time system.

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Quantification of element transport mechanisms and -rates in metamorphic rocks is most challenging as it allows precise prediction and quantification of ore- and rock-forming processes. Garnet porphyroblasts and their compositional growth zonations display an excellent record of element transport within their host rocks, as they precisely reflect the interplay between thermodynamically controlled nutrient demand and kinetically constrained element availability during growth. Extraction of this valuable information is hindered by the fact that the interplay of different rate-limiting factors on garnet growth and -composition are not fully understood. In this project we will use an intergrated multi-method approach where the results of thermodynamic-, nucleation-, diffusion-, and trace element-modeling of garnet growth are compared with natural observations derived from 3D-tomographic and in situ trace-element analyses. This combination will be applied to samples from different tectonometamorphic settings that excellently preserve various typical and characteristic garnet growth patterns with plenty of information readily available from published data. Our approach will yield crucial information about reaction paths, element transport-mechanisms and -rates as well as their reflections in growth patterns in garnet. Such information facilitates interpretations of characteristic compositional features in garnet in terms of geodynamic and geochemical processes.