柔性断层错动产物的微观研究方法初探

AN INITIAL RESEARCH ON MICROSCOPIC METHOD FOR PLASTIC FAULT DISLOCATION PRODUCTS

柔性断层错动产物一般尚未固结,难以对其进行定向取样,固化和磨制薄片,笔者经过长期努力提出解决这个问题的方法并将其应用于郯—庐断裂带赤山段晚更新世以来活动性的研究中。笔者按总结出的方法定向采取断层泥,对其固化并磨制定向薄片,在镜下仔细观测,发现众多变形现象和由其反映的运动学和动力学方面的重要信息。属脆性变形的有:长英质矿物颗粒被错移并形成棋盘格式构造,脆—塑或塑性变形发生在粘土和云母类的矿物中,尤其是“帚”状扭折和先扭后错现象在云母中非常普遍。恢复薄片的自然产状后,宏微观构造具统一性。据变形产物赋存的地质时代,它们应是断裂晚更新世以来活动的微观证据。文中笔者除系统介绍了柔性断层产物的采样、固结、磨片和应用此种技术的实例外,还探讨了显微构造分析在活断层研究中应有的地位和作用。

Generally, the dislocation products of plastic faults are not consolidated, therefore it is difficult to get oriented sampling, make them consolidated and grind slices. The authors have proposed a method to solve this problem, and have applied it to the Chishan segment of the Tangcheng-Lujiang fault zone. The fault gouges were sampled, consolidated and grinded into slices with the proposed method, and abundant deformation phenomena which reflect lots of important information of kinematics and dynamics were found under a microscope, such as the brittle deformation-the felsic minerals were dislocated and lineament structures were formed and brittle-ductile or ductile deformation was developed in clay and mica minerals. After restoring the natural stages of those slices, the microscopic and macroseopic structures were coincided with cach other. It is obvious that they might be the microscopic evidences of fault since Late Pleistocene,, Finally, the authors discussed the position and function of the microscopic analysis in the research of active faults.