Koehn, D., Bons, P.D., Hilgers, C. & Passchier, C.W. 2001. Animations of progressive fibrous vein and fringe formation. In: Ailleres, L. and Rawling, T. 2001. Animations in Geology. Journal of the Virtual Explorer, 4.
Animations of progressive fibrous vein and fringe formation

D. Koehn1, P.D. Bons2, C. Hilgers3, C.W. Passchier2

Revised Version posted - 28 June 2001

1Center for Advanced Studies, The Norwegian Academy of Science,
Drammensveien 78, N-0271 Oslo, Norway;
E-Mail: daniel.kohn@shs.uio.no
2Tectonophysics, Institut für Geowissenschaften, Universität Mainz, D-55099, Germany
3Geologie - Endogene Dynamik, RWTH Aachen, D-52056, Germany
 

Abstract

We developed two programs, "Vein Growth" and "Fringe Growth", to investigate progressive growth of crystals in dilation sites (veins and strain fringes). Even though these models are based on a simple anisotropic growth function, they produce complex textures that compare well with natural examples of veins and strain fringes. In our simulations the most important factor that controls the crystal shape in the dilation site is the roughness 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. Fibrous crystals (crystals with a high length to width ratio) which can track the opening trajectory of the dilation site will develop 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 and if crystals grow fast enough to close the site. The width of fibres depends on the number of initial nuclei and on the distance of adjacent asperities on the wall-rock- or core-object surface. Our simulations suggest that single fibres should not be used for structural analysis especially in the case of strain fringes since relative rotation between fringes and core-object influences fibre-growth directions. We discuss the implications of our modelling results for the use of crystal textures in veins and strain fringes for structural analysis.


keywords: vein, strain fringe, texture, fibre, crack-seal

Index:

Introduction

Programs

Textures

Structural Analysis

Conclusion

References