Stress orientation and fracturing during three-dimensional buckling: Numerical simulation and application to chocolate-tablet structures in folded turbidites, SW Portugal
Stress orientation and fracturing during three-dimensional buckling: Numerical simulation and application to chocolate-tablet structures in folded turbidites, SW Portugal
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三维屈曲过程中的应力定向和断裂：葡萄牙西南部折叠浊积岩巧克力片结构的数值模拟及其应用
DOI：
10.1016/j.tecto.2010.07.016
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发表时间：
2010
期刊：
影响因子：
2.9
通讯作者：
J. Burg
中科院分区：
文献类型：
--
作者：
J. Reber;S. Schmalholz;J. Burg
葡萄牙西南部石炭纪浊积岩的褶皱石英杂岩的边缘上，有两组垂直于层理的垂直脉，形成巧克力片状结构。结构观察表明，（1）模式1骨折形成的褶皱轴横向时，褶皱振幅小，并在层的平行压缩和（2）模式1骨折形成的褶皱轴平行时，褶皱振幅大，并带来了层的平行拉四肢。我们进行了二维和三维的数值模拟调查粘性折叠过程中的应力方向的演变，以测试是否以及如何这两组连续的骨折折叠。我们采用椭圆和椭球的可视化和量化的局部应力场。数值模拟结果表明，褶皱翼中局部σ 1方向相对于层面的方位变化近90°。同时期σ 3方向由低振幅时平行于褶皱轴旋转到高振幅时垂直于褶皱轴。多层膜的应力方向变化比单层膜快。数值模拟是一致的观察，并提供了一个机械解释的形成巧克力片结构，通过连续组的骨折旋转四肢折叠主管层。
Two orthogonal sets of veins, both orthogonal to bedding, form chocolate tablet structures on the limbs of folded quartzwackes of Carboniferous turbidites in SW Portugal. Structural observations suggest that (1) mode 1 fractures transverse to the fold axes formed while fold amplitudes were small and limbs were under layer-subparallel compression and (2) mode 1 fractures parallel to the fold axes formed while fold amplitudes were large and limbs were brought to be under layer-subparallel tension. We performed two- and three-dimensional numerical simulations investigating the evolution of stress orientations during viscous folding to test whether and how these two successive sets of fractures were related to folding. We employed ellipses and ellipsoids for the visualization and quantification of the local stress field. The numerical simulations show a change in the orientation of the local σ1direction by almost 90° with respect to the bedding plane in the fold limbs. The coeval σ3direction rotates from parallel to the fold axis at low fold amplitudes to orthogonal to the fold axis at high fold amplitudes. The stress orientation changes faster in multilayers than in single-layers. The numerical simulations are consistent with observation and provide a mechanical interpretation for the formation of the chocolate tablet structures through consecutive sets of fractures on rotating limbs of folded competent layers.