Tablet boudinage of an anhydrite layer in rock-salt matrix: Results from thermomechanical experiments
Tablet boudinage of an anhydrite layer in rock-salt matrix: Results from thermomechanical experiments
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DOI：
10.1016/j.jsg.2011.09.006
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发表时间：
2011-12
影响因子：
3.1
通讯作者：
J. Zulauf;G. Zulauf;J. Hammer;F. Zanella
中科院分区：
文献类型：
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作者：
J. Zulauf;G. Zulauf;J. Hammer;F. Zanella
嵌入无能力岩盐基质中的单个有能力的硬石膏层，在温度 T = 345 °C、应变速率 ė = 10−7s−1 下以扁平型体积变形变形，达到最大有限应变 eZ= −30%。由于硬石膏层的取向垂直于主缩短方向 Z，因此该层在所有方向上均经历等层平行延伸，从而形成片状布丁。布丁格由硬石膏的拉伸断裂产生。另一方面，岩盐基质表现出粘性。石盐的晶体塑性变形通过{110}<110>上的滑移来调节，这导致亚晶粒的形成和旋转以及平行于主缩短轴Z的001-最大值。然而，石盐的轴对称织构仅存在于与硬石膏层接触处的高应变域中，其中从石盐的亚晶尺寸获得的差异应力达到了最大值约100。 6 兆帕。远离硬石膏层的亚颗粒产生 2-3 MPa，这与机器称重传感器记录的流动应力一致。平面视图中片剂布丁的非等距形状由长轴和短轴之比 (R = 1.2–1.9) 表示，并且可以通过同心和径向拉伸断裂的相互作用来解释。平面视图中片剂布丁的平均直径 Wa 和布丁的数量 N 均与层厚度呈线性关系。渐进的有限应变导致布丁的数量增多和平均直径变小。布丁的厚度 Hf 与初始层厚度 Hi 几乎相同，而纵横比 (Wd= Wa/Hf) 随着有限应变而减小。从所有运行中获得的平均 Wd 值范围为约。 0.8 至约。 1.5.该范围远低于粘性层或脆性/粘性层中布丁的长宽比，但与裂缝饱和模型预期的长宽比相似。片状硬石膏布丁的长宽比进一步与迄今为止公布的在平面或收缩类型的块体变形中形成的拉伸断裂布丁的长宽比一致。
A single competent layer of anhydrite, embedded in a matrix of incompetent rock salt, was deformed in a flattening type of bulk deformation at temperature, T = 345 °C, strain rate, ė = 10−7s−1, to a maximum finite strain, eZ= −30%. As the anhydrite layer was oriented perpendicular to the main shortening direction, Z, the layer underwent equal layer-parallel extension in all directions resulting in tablet-shaped boudins. Boudinage results from tensile fracture of anhydrite. The rock-salt matrix, on the other hand, behaved viscously. Crystal plastic deformation of halite was accommodated by slip on {110}<110> which led to formation and rotation of subgrains and a 001-maximum parallel to the principal shortening axis, Z. An axisymmetric texture of halite, however, is present only in high-strain domains at the contact to the anhydrite layer where the differential stress, obtained from subgrain size of halite, reaches maximum values of ca. 6 MPa. Subgrains remote from the anhydrite layer yielded 2–3 MPa, which is consistent with the flow stress recorded by the load cell of the machine. The non-isometric shape of the tablet boudins in plan-view is indicated by the ratio between long and short axis (R = 1.2–1.9), and can be explained by the interaction of concentric and radial tensile fractures. Both the mean diameter of the tablet boudins in plan-view, Wa, and the number of boudins, N, show a linear relation to the layer thickness. Progressive finite strain results in a higher number and a smaller mean diameter of the boudins. The thickness of the boudins, Hf, is almost the same like the initial layer thickness, Hi, while the aspect ratio (Wd= Wa/Hf) decreases with finite strain. The mean Wdvalues obtained from all runs are ranging from ca. 0.8 to ca. 1.5. This range is much lower than the aspect ratio of boudins in viscous or brittle/viscous layers, but is similar to the aspect ratio expected from fracture-saturation models. The aspect ratio of the tablet-shaped anhydrite boudins is further consistent with aspect ratios published so far for tensile-fracture boudins which developed in a plane or constrictional type of bulk deformation.