Development of crystal morphology during unitaxial growth in a progressively widening vein: I. The numerical model

A two-dimensional numerical model for the simulation of the formation of microstructures in crack-seal veins is presented here. The grain aggregate in the vein is described by grain boundary nodes that link short, straight boundary segments. Growth of crystals into a crack takes place by many small incremental movements of nodes. The rate of growth depends on the chosen growth morphology of the vein-forming material. Different growth morphologies can be defined. For every user-defined number of steps, the wall rock is moved a user-defined distance and direction, which simulates the opening of a crack, after which sealing can proceed again. The shape of the crack-surface (e.g. smooth or with ridges) can be set by the user and can be made to match fracture surfaces found in real rocks. The model is capable of reproducing realistic crack-seal textures and can be used to systematically investigate the role of different parameters on the microstructures of veins. First applications of the model are presented in Part II of this paper (this volume).