Formation of radiator structures in quartz veins - Phase-field modeling of multi-crack sealing

Abstract

The present work showcases a comprehensive phase-field study on the formation of multi-crack-seal veins in quartz microstructures. The microstructure simulation framework Pace3D incorporates the modeling of both fracturing and sealing in polycrystalline rock systems, where crystallographic anisotropies, crack resistances and growth velocities of different facets are included in the energy density contributions. In a two grain system we exemplary show the formation of three different archetypes of radiators which are observed in natural quartz veins. We extend the phase-field studies to a polycrystalline host rock and investigate therein the effects of fracture aperture, presence of accessory minerals, and oblique opening trajectories with refracturing of fully and partially sealed veins on the occurring vein crystal morphology. Our results show that the shape of the forming grain boundaries depends on the crystal orientation of the participating grains, the location of a fracture through the crystals, and the sealing state. Evolution of more pronounced radiator structures are found in simulation studies with increasing aperture. A broad spectrum of crystal structures which are frequently observed in natural quartz vein microstructures is reproduced in simulations using the combined crack-seal phase-field model.