陆-陆碰撞造山带动力学成因机制的物理模拟实验

PHYSICAL MODEL EXPERIMENTS OF DYNAMIC MECHANISM ON CONTINENT CONTINENT COLLISION

报道了利用自行研制的ＧＪ１ 型物理模拟实验装置实施的陆 陆碰撞造山带形成和演化动力学过程的最新实验结果。实验结果表明，陆 陆碰撞是岩石圈或地壳缩短和增厚的主要机制之一。在地幔对流派生的拖曳力和板块相互运动产生的压缩力以及其它附加力的联合作用下，模型长度和厚度分别缩短４５ ％ 和增厚８５ ％ 是可能的。推覆造山作用有可能将下地壳的岩石物质和构造推覆到上地壳或地表，形成在地表可观察到的韧性剪切带构造。推覆体中的逆冲断层系往往沿最为发育的一组剪切面形成和演化，被叠置或双重地层的形成使地壳厚度明显增加。实验结果展示出推覆造山带、俯冲带和混杂岩带三个主要构造单元的形成和演化的动力学过程，以及它们之间的构造动力学和几何学关系。认为：陆 陆碰撞造山带是在地幔对流派生的拖曳力和板块相互运动产生的压缩力以及其它附加力联合作用下形成和演化的，大洋闭合和二个大陆之间的对接与碰撞导致了造山作用的发生，混杂岩带的形成和演化与洋壳俯冲作用密切相关。

Physical model experiments of continent continent collision is performed with a new apparatus. The apparatus used in the experimentation consists of a large box(100cm long, 70cm high and 12cm wide) with two motor drives. It is possible that the rotational speed of motor drive may changes in 1～2800r/min to simulate the drive forces of the mantle convection. Experimental results have already indicated that the continent continent collision is one of the principal mechanism to lead to lithosphere/crust thickening and mountain building. The models are shortened and thickened about 45% and 85% respectively under the combined actions of the viscous drag exerting on the base of the lithosphere and of the lateral motion of the top mantle convection cells from deep mantle, and compressive forces from plate movement in the experimental conditions. Early stage of the model is shown in Fig.2(a) in this paper. The evolutionary relationship between napping/mountain building and subducting can be observed from photograph of experimental model in Fig.2(e) in this paper.