High-strain zones: a unified model
High-strain zones: a unified model
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DOI：
10.1016/s0191-8141(98)00025-x
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发表时间：
1998-08
影响因子：
3.1
通讯作者：
D. Jiang;P. Williams
中科院分区：
文献类型：
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作者：
D. Jiang;P. Williams
当剪切带以未变形的围岩为界，并且没有体积变化时，在整体尺度上，剪切带内的变形路径近似于简单剪切。当带边界被拉伸并且两个边界之间的剪切方向平行于边界的主拉伸方向之一时，带内的变形路径不是简单的剪切，而是仍然具有单斜对称性。简单剪切和一般单斜变形路径都应视为自然界中的特殊情况，因为通常不仅带边界是拉伸的，而且剪切也斜向于边界的主拉伸方向。在这种一般情况下，变形路径是三斜的。我们建立了一个模型，其中包括这种一般情况下，也考虑到体积变化。需要五个独立的参数来表征流动的变形速率;四个足以表征流动运动学。该模型通常是三斜晶系，正交和单斜变形是子群。通过改变表征参数的值，可以表示各种类型的高应变区。在这种区域内流动的运动学和累积有限变形的几何形状进行了研究。许多野外观察结果，例如，在横向剪切带中的线理，在垂直和水平之间变化，劈理横切褶皱，以及在一些剪切带中没有鞘褶皱，其中褶皱已被显着旋转，有时可以更好地解释在我们的一般模型的背景下。
Where a shear zone is bounded by undeformed wall rocks and there is no volume change, the deformation path within the zone on the bulk scale approximates a simple shear. Where the zone boundaries are stretched and the shear direction between the two boundaries is parallel to one of the principal stretching directions of the boundaries, the deformation path within the zone is not a simple shear but still has monoclinic symmetry. Both simple shear and general monoclinic deformation paths should be regarded as special cases in nature, because generally not only are the zone boundaries stretched but also the shear is oblique to the principal stretching directions of the boundaries. In this general case, the deformation path is triclinic. We establish a model which includes this general case also taking into consideration volume change. Five independent parameters are required to characterize the rate of deformation of the flow; four are sufficient to characterize the flow kinematics. The model is generally triclinic, and orthorhombic and monoclinic deformations are subgroups. By varying the values of the characterizing parameters, the various types of high-strain zones can be represented. The kinematics of flow within such zones and the accumulated finite deformation geometry are investigated. Many field observations such as, for example, lineations in transcurrent shear zones that vary between vertical and horizontal, cleavage transected folds, and the absence of sheath folds in some shear zones where folds have been significantly rotated, can sometimes be better interpreted in the context of our general model.