Mechanisms of flexural flow folding of competent single-layers as evidenced by folded fibrous dolomite veins
Mechanisms of flexural flow folding of competent single-layers as evidenced by folded fibrous dolomite veins
复制标题
折叠纤维白云石脉证明的单层弯曲流动折叠机制
DOI：
10.1016/j.jsg.2014.10.002
复制
发表时间：
2014
影响因子：
3.1
通讯作者：
M. Sintubin
中科院分区：
文献类型：
--
作者：
K. Torremans;P. Muchez;M. Sintubin
弯曲流动被认为不太可能发生在自然变形的、各向同性的单层中。在这项研究中，我们讨论了一个特殊的情况下，折叠层状平行纤维白云岩脉页岩，其中内部应变模式和显微结构变形功能提供了新的见解的机制，使弯曲流动折叠。应变在预褶皱脉是由两个主要机制：晶内变形弯曲和晶间变形与书架旋转的白云岩纤维。最初正交的白云石纤维允许重建褶皱矿脉上的应变分布。该分析表明，由纤维产生的平面机械各向异性导致静脉近似弯曲流动。在褶皱过程中，同运动脉覆盖在褶皱前的纤维状白云岩脉之上。显微结构和白云岩生长形态反映了褶皱演化过程中的生长，并有褶皱锁定时挠曲滑动的证据。均匀的扁平，证明了分离轴面劈理，随后修改这些褶皱从1B级到1C褶皱。我们的研究表明，内部静脉组构有一个一阶的折叠运动学的影响。此外，纤维状白云岩脉显示出与页岩基质相比的高粘度，这对于在渐进褶皱期间在后期同运动脉中为后续矿化阶段创造瞬时渗透性至关重要。
Flexural flow is thought unlikely to occur in naturally deformed, competent isotropic single-layers. In this study we discuss a particular case of folded bedding-parallel fibrous dolomite veins in shale, in which the internal strain pattern and microstructural deformation features provide new insights in the mechanisms enabling flexural flow folding. Strain in the pre-folding veins is accommodated by two main mechanisms: intracrystalline deformation by bending and intergranular deformation with bookshelf rotation of dolomite fibres. The initially orthogonal dolomite fibres allowed a reconstruction of the strain distribution across the folded veins. This analysis shows that the planar mechanical anisotropy created by the fibres causes the veins to approximate flexural flow. During folding, synkinematic veins overgrow the pre-folding fibrous dolomite veins. Microstructures and dolomite growth morphologies reflect growth during progressive fold evolution, with evidence for flexural slip at fold lock-up. Homogeneous flattening, as evidenced by disjunctive axial-planar cleavage, subsequently modified these folds from class 1B to 1C folds. Our study shows that the internal vein fabric has a first-order influence on folding kinematics. Moreover, the fibrous dolomite veins show high viscosity contrasts with the shale matrix, essential in creating transient permeability for subsequent mineralising stages in the later synkinematic veins during progressive folding.