CRYSTALLIZATION IN FLOW - II. MODELLING CRYSTAL GROWTH KINETICS CONTROLLED BY BOUNDARY LAYER THICKNESS

Abstract

As in several other anisotropy of magnetic susceptibility studies, the main direction of the magnetic lineation analysed in part I of this work, as well as crystal elongation, have been found to be roughly aligned with the direction of the surrounding flow. In order to explain the mechanisms responsible for such crystal shape anisotropy in a hydrodynamic context, we derive a mathematical model based on Falkner-Skan self-similar boundary layers at high Reynolds numbers. The model allows calculating local growth rates out of diffusion processes in the concentration boundary layer for crystal faces orientated arbitrarily in the range 90° to -18° with respect to the flow direction, and for any flow velocity. Hence, our work generalizes rationally previous attempts already done in the case of a flow parallel to the crystal face. This crystal growth model is applied to a natural case of calcite growth rate in 2-D section perpendicular to the 〈c〉 axis. The reconstructed calcite growth reproduces the texture of a natural case observed in Part I, although the local Reynolds numbers are quite low. This approach may be applied for various geological settings, from deep metasomatism to flowing on the Earth surface. © 2006 The Authors Journal compilation © 2006 RAS.