裂谷模拟实验及其地质意义

THE MODEL EXPERIMENT OF THE RIFT SYSTEM AND ITS GEOLOGICAL IMPLICATIONS

选用多种松散材料模拟了“上涌型”裂谷的形成演化过程。详细描述了裂谷模型的变形特征与演化过程,着重讨论了边缘逆断层和下部陡立断裂的性质及成因机制,表明模型变形是在顶部拉伸、上部两侧挤压、中下部剪切的应力状态下所形成,且整个应力场随模型层的变形与边界条件的改变而演变。对模拟实验的相似问题与实验结果进行对比讨论,表明模型和原型在主要物理条件和变形特征方面都极为相似。最后,讨论了本模型实验的地质意义。

This paper describes in detail the deformation process of model layers of a rift, and the discussion centres on the mechanism of the low-angle thrust faults on both sides of the graben at the top of the model layers and the deepseated high-angle shear(or normal)faults. Its geological implication is put forward in the end.The dynamic force is the upthrusting force coming from the bottom of the layers which simulates mantle upwelling. The deformation process may be largely divided into four stages in developing order: (1) an arch of the layers, (2) a depressed graben, (3) thrust faults and shear faults, and (4) thrust-shear composite faults. The stress field is not homogeneous, the model is in a state of tension at the top, in a state of compression on both sides of the top and in a shear state in the lower part.The geological implications are as follows:1. The deformation process represents the evolutional process and formation mechanism of the graben down-faulted basin.2. The thrust faults and graben have formed in the same tectonic stress field, so both of them are the components of the 'upwelling' rift system.3. From an indirect source the result of the experiment shows that taphrogenesis and orogenesis coexist in space and follow each other closely in time.