Chen S P, Tian Z J, Xu S D, Ma Z Z, Chang S Y, Zhao H B. Two structural types of shear fracture belts related to wrenches. Geological Bulletin of China, 2024, 43(1): 13−19. DOI: 10.12097/gbc.2023.04.005
    Citation: Chen S P, Tian Z J, Xu S D, Ma Z Z, Chang S Y, Zhao H B. Two structural types of shear fracture belts related to wrenches. Geological Bulletin of China, 2024, 43(1): 13−19. DOI: 10.12097/gbc.2023.04.005

    Two structural types of shear fracture belts related to wrenches

    • Riedel shears are the typical structural styles in strike-slip belts. However, shear fracture zones have been found recently to have different shear fracture assemblages. In these shear fracture belts, the properties of the arraying patterns of the shear fractures are identical with those of the moving ways of the two fault blocks, which is either left-step with left-lateral movement or right-step with right-lateral movement. The shear fractures are called homo-step-slip ones. These oversteps between two shear faults are divergent. Based on the Coulomb fracture theory, it is suggested that the shear fracture belts would be formed in the fault blocks between two wrench belts. In these cases, two conjugate potential shear faults would be formed along the maximum principal stress trajectories. In the progressive deformation, the shears with smaller acute angle to the maximum shear stress (principal strike-slip) trajectories have priority to develop. The shears with bigger acute angle to the maximum shear stress trajectories would be delimited between the former shears. A new-type shear fracture belt is formed different from the typical Riedel shears in shear fracture assemblages. This shear fracture belt will be favorable for both hydrocarbon accumulation and mineral deposit formation due to the divergent oversteps.
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