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Weak-link minerals in crystalline rock: How mica cleavage orchestrates fracture propagation?
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DOI：10.1016/j.jrmge.2026.06.019.png)
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Abstract
En 中文
Mica, acting as a weak-link mineral, exerts disproportionate control over the fracture evolution of granitic rocks owing to its perfect cleavage and pronounced anisotropy. However, when numerically modeling mica-bearing rocks, conventional grain-based models (GBMs) tend to oversimplify mica as isotropic grains similar to quartz and feldspar, thereby failing to capture cleavage-controlled propagation and crack deflection. To bridge this gap, we propose a computed tomography (CT)-derived cleavage grain–based modeling (CT-CGBM) method that integrates high-resolution X-ray CT with nanoindentation to explicitly reconstruct the laminar cleavage structure of mica. The proposed model accurately reproduces the experimental stress-strain response (error <5%) and failure morphology, while effectively capturing complex mica-related cracking. At the mesoscopic scale, microcracks preferentially initiate within mica interlayers and at mica grain boundaries, before propagating into adjacent minerals. The normalized crack coefficient indicates that the most pronounced damage occurs within mica grains ( = 15.243%), with grain-boundary damage exceeding intragranular damage. At the macroscopic scale, mica cleavage reduces the peak strength and elastic modulus by 2.46% and 3.25%, respectively, and increases the Poisson’s ratio by 8.2%. Slip and opening driving coefficients reveal coupled control of the local stress ratio and the angle on mica instability. Moderate dip angles ( = 56° or 124°) promote slip along mica cleavage planes, and higher lateral tensile stress triggers opening over a wider range. This study reveals the controlling mechanisms of the weak-link mineral mica on crack propagation in granite at the mineral scale.
Keywords:
Mica cleavage structure
Grain-based modeling
Realistic mineral characteristics
Mineral scale
Cracking characteristics
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