韧性剪切带糜棱岩中不对称旋转碎斑系剪切指向模拟实验韧性剪切带糜棱岩中不对称旋转碎斑系剪切指向模拟实验研究现状及其问题

韧性剪切带是大陆变形过程中形成于地壳深层次的重要构造变形形迹，是重建构造变形温压环境、变形几何学、运动学及动力学的重要研究对象。剪切变形方向的确定是韧性剪切带研究的基础环节之一。尽管指示韧性剪切带剪切方向的标志很多，但是由于韧性剪切带变形过程的复杂性，实际工作中往往很难准确地限定剪切方向，甚至常常会发现同一条韧性剪切带中发育指向相反的剪切标志。在变形岩石中，不对称旋转碎斑系被认为是判断韧性剪切带剪切方向的可靠标志。根据有拖尾的旋转碎斑系判断剪切指向要比“云母鱼”、“多米诺”等组构可靠得多。总结前人的理论和模拟试验成果，可以清楚地认识到，碎斑系的演化是其形态、轴率、初始方位、基质及其界面性质、运动学涡度、剪应变强度、剪切带的厚度、碎斑短轴比等因素综合作用的结果。深刻认识不对称旋转碎斑系在韧性剪切带形成过程中的发育过程、限制条件、影响因素，将有助于准确地运用它们来判断韧性剪切变形的构造指向，以便进一步研究与该韧性剪切变形相关的大陆动力学。

Current situation of research on the simulating experiments on the shear direction of asymmetry rotated porphyroclast in the ductile shear zone of mylonites. Geological Bulletin of China

Ductile shear zone is an important structural trace during the continental deformation process in deep-seated crust, it is an important research object for the reconstruction of the P-T condition, deformation geometry, kinematics and dynamics of the structural deformation. The shear direction is the most important and fundamental basis for the ductile shear zone research. Although, there are many indicators, because of the complexity of the deformation process, it is always difficult to define the shear direction, sometimes incompatible shear direction indicators can be observed within the same ductile shear zone. Asymmetry rotated porphyroclast system is considered as the most credible indicators to indicate the shear direction. In comparison with “mica-fish” and “domino” structure, porphyroclast system with tails is more dependable for shear direction recognition. Theoretical and simulating experiments have proved that evolution of porphyroclasts are influenced by various factors including shape, axis rate, initial orientation, matrix, viscosity of the particle/matrix interface, kinematic vorticity, intensity of shear strain, shear zone thickness and shorter axis ratio. With the help of understanding of development process, restricted conditions, influence factors of porphyroclast systems within the ductile shear zone, structural direction can be defined as to further probe into its related continental dynamic features.