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

元素在变质岩中的迁移机制和速率的量化是最具挑战性的，因为它可以精确地预测和量化成矿和成岩过程。石榴石成斑岩及其成分生长分带显示了寄主岩石内元素迁移的良好记录，因为它们准确地反映了生长过程中热力学控制的营养需求和动力学限制的元素可用性之间的相互作用。由于不同的速率限制因素对石榴石生长和成分的相互作用尚未完全了解，这一有价值的信息的提取受到了阻碍。在这个项目中，我们将使用一种综合的多方法方法，将石榴石生长的热力学、成核、扩散和微量元素模拟的结果与来自3D-CT和原位微量元素分析的自然观测结果进行比较。这一组合将应用于来自不同构造变质环境的样品，这些样品很好地保存了各种典型和特征的石榴石生长模式，并从已公布的数据中随时可以获得大量信息。我们的方法将提供关于反应路径、元素迁移机制和速率的关键信息，以及它们在石榴石生长模式中的反映。这些信息有助于从地球动力学和地球化学过程的角度解释石榴石的特征成分特征。

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.