Extension fracture propagation in rocks with veins: Insight into the crack‐seal process using Discrete Element Method modeling

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Abstract
We investigate how existing veins interact with extension fractures in rocks using 3‐D Discrete Element Method models with a geometry inspired by tension tests with notched samples. In a sensitivity study, we varied (a) the angle between the vein and the bulk extension direction and (b) the strength ratio between host rock and vein material. Results show a range of vein‐fracture interactions, which fall into different, robust, “structural styles.” Veins, which are weaker than the host rock, tend to localize fracturing into the vein, even at high‐misorientation angles. Veins, which are stronger than the host rock, cause deflection of the fracture tip along the vein‐host rock interface. Fractures are arrested at the interface from weak to stronger material. When propagating from a stronger to a weaker material, macroscopic bifurcation of the fracture is common. Complex interactions are favored by a low angle between the vein and the fracture and by high‐strength contrast. The structural styles in the models show good agreement with microstructures and mesostructures of crack‐seal veins found in natural systems. We propose that these structural styles form the basis for criteria to recognize strength contrasts and stress of crack‐seal systems in nature.

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