岩石圈塑性流动网络与多层构造变形的物理模拟

PHYSICAL MODELLING OF PLASTIC FLOW NETWORK AND MULTI LAYER TECTONIC DEFORMATION IN THE LITHOSPHERE

采用塑化松香作为岩石圈延性下层的相似材料，进行了板内塑性流动网络及多层构造变形的物理模拟实验。延性单层模型的实验表明，在边界挤压或“高原”重力势的作用下，依赖于延性层粘度的高低不同，主要形成剪切网络、压性褶皱以及二者过渡型式等一级构造。在延性／脆性双层模型中（脆性上层和延性下层分别相当于岩石圈上、下层），边界驱动力的远程传递，主要借助于延性下层的网络状流动，岩石圈下层（含下地壳和岩石圈地幔）的剪切网络，即塑性流动网络，控制着板内构造变形，导致脆性上层内剪切破裂网络、逆推断裂、纵向张裂以及其它次级断裂和褶皱的发育。实验还表明，上、下层之间非连续分布的软弱夹层（模拟壳内低速、高导层）并不妨碍下层塑性流动网络的扩展，但影响牵引力的向上传递及上层构造变形的强弱分布。

The use of plasticized rosin as an analog material of the ductile lower lithosphere provides an effective approach to modelling intraplate plastic flow network and multi layer tectonic deformation. The experiments of ductile single layer models indicate that under the action of compression at the plate boundary or gravity potential of “plateau” the first order tectonic patterns, including those of shear network, compressional fold, or their transitional type, are observed respectively corresponding to the condition of relatively high, low, or moderate viscosities. In the ductile/brittle two layer model with solidified talc powder slurry as its britte upper layer the long range transmission of driving force at the plate boundary is carried out mainly by netlike flow through the ductile lower layer, and, therefore, the shear network, i.e. plastic flow network, in the lower lithosphere controls the intraplate tectonic deformation resulting in the development of shear fracture network, thrust faults, longitudinal tension fractures, and other secondary order faults or folds in the brittle upper layer. The experiments also show that the discontinuously distributed partings of weakness, which model low velocity or high conductivity layer in the crust, do not obstruct spreading of plastic flow network in the lower layer, though influence the upward transmission of drag force and the distribution of intensity of tectonic deformation in the upper layer.