Animations of progressive fibrous vein and fringe formation

Abstract

Abstract: We developed two programs, Vein Growth and Fringe Growth, to investigate progressive growth ofcrystals in dilation sites (veins and strain fringes). Even though these models are based on a simple anisotropicgrowth function, they produce complex textures that compare well with natural examples of veins and strainfringes. In our simulations the most important factor that controls the crystal shape in the dilation site is theroughness of the growth surface (defined by asperities on the wall-rock of veins or core-object of fringe structures)and the amplitude of these asperities relative to the width of the dilation site after an opening-event. Fibrouscrystals (crystals with a high length to width ratio) which can track the opening trajectory of the dilation site willdevelop if grain boundaries of crystals are locked to asperities on the wall-rock of veins or core-object of fringes.This happens only if the amplitude of the asperities is large relative to single opening steps of the dilation site andif crystals grow fast enough to close the site. The width of fibres depends on the number of initial nuclei and onthe distance of adjacent asperities on the wall-rock- or core-object surface. Our simulations suggest that singlefibres should not be used for structural analysis especially in the case of strain fringes since relative rotationbetween fringes and core-object influences fibre-growth directions. We discuss the implications of our modellingresults for the use of crystal textures in veins and strain fringes for structural analysis. keywords: vein, strain fringe, texture, fibre, crack-seal