3D Rock-Microstructure Modelling by the use of an Automated Fabric Analyser

For approximately 150 years, the thin section microscopy is the most important technique in classical petrology and is still taught at almost every geology department. Besides determining the mineral composition of a rock, the analysis of rock thin sections under polarized light enables us to determine 2D properties of the mineral assemblages such as their spatial distribution, size and shape and, some limited information about their crystallographic orientation. On the other hand, only few and often indirect 3D information such as elongation of minerals or planar arrangement can be gained from orthogonal thin sections within the same sample. We will develop algorithms and a software package to construct 3D rock microstructure models from 2D thin sections analysed with a new automated Fabric Analyser. We will use the specific light arrangement of the Fabric Analyser to illuminate the sample from different directions using single and crossed polarized light. Based on the resultant images, mathematical algorithms will be developed to label grains and determine grain boundary orientations of neighbouring grains. Together with c-axis orientation measurements analysed with the Fabric Analyser, the algorithms will be extended to calculate misorientations between the measured orientation and the real crystal structure. The software will include 3D shape grain boundary reconstruction of minerals, fractures and inclusions. Such 3D models will improve our understanding of how rocks form during time and deformation.

This research project is carried out in close collaboration with Dr. Ralf Schulze (Universitätsmedizin)