The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing
The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing
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DOI：
10.1002/2014jb011520
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发表时间：
2014-12
期刊：
影响因子：
--
通讯作者：
S. Virgo;S. Abe;J. Urai
中科院分区：
文献类型：
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作者：
S. Virgo;S. Abe;J. Urai
矿脉在上、中地壳岩石中普遍存在。由于与主岩的强度和刚度对比，矿脉会影响裂纹扩展。在这里，我们提出了离散元模型，通过模拟岩体破裂、密封裂缝形成脉以及旋转应力场后岩体再次破裂的循环来研究裂纹与脉的相互作用。我们观察到新裂缝和现有矿脉之间不同类型的相互作用，这取决于矿脉和主岩之间的强度比以及不同变形阶段之间应力场的变化。如果变形阶段之间应力场的方向不发生变化，则如果脉较弱，则产生同轴裂纹封闭脉；如果脉较强，则产生一束近平行的微脉。如果应力场在变形阶段之间旋转，则相互作用包括再激活、裂缝偏转和横切。即使静脉方向相对于应力场非常不利，也会发生弱静脉的重新激活。重新激活的静脉之间的骨折中继形成与静脉的角度高于预期。这表明次生脉的方向不能以简单的方式反映区域应力场，并且脉可以强烈影响裂缝的连通性，这对古应力分析和盆地建模具有重要意义。模拟结果与阿曼 Jebel Akhdar 碳酸盐岩多相脉网络的现场实例相比较。
Veins are ubiquitous in upper and middle crustal rocks. Due to strength and stiffness contrast to the host rock, veins can influence crack propagation. Here we present Discrete Element Models to investigate crack‐vein interactions by simulating cycles of fracturing of a rock mass, sealing the cracks to form veins, and refracturing the rock mass after rotating the stress field. We observe different styles of interaction between new fractures and existing veins, depending on the strength ratio between vein and host rock and on the changes in the stress field between the different deformation stages. If the orientation of stress field does not change between deformation stages, ataxial crack seal veins are produced if the veins are weak and a bundle of subparallel microveins if the veins are strong. If the stress field is rotated between deformation stages, the interactions include reactivation, fracture deflection, and crosscutting. Reactivation of weak veins occurs even if the vein orientation is highly unfavorable relative to the stress field. Relays of fractures between reactivated veins form at a higher angle to the veins than expected. This demonstrates that the orientation of secondary veins does not reflect the regional stress field in a simple manner and that veins can strongly influence fracture connectivity, with implications for paleostress analysis and basin modeling. Simulation results compare well with field examples of multiphase vein networks in carbonates from Jebel Akhdar, Oman.