论文部分内容阅读
殷店—马垅(简称殷马)韧性剪切带是桐柏—大别造山带南缘的一条重要的边界断裂,对其精细的构造变形研究将有助于进一步认识桐柏—大别造山带的演化方式和过程。本文主要对殷店和马垅两个地区进行了详细的剖面观测,利用有限应变测量,计算出殷马剪切带中岩石应变椭球长短轴的平均轴率为1.69,靠近剪切带的岩石应变量大,向北远离剪切带,应变量减小;通过构造应力场分析查明剪切带的古应力状态,最大压应力σ_1为北北东—南南西向,对应最大拉应力σ_3为北西西—南东东向。岩石的有限应变分析和应力场状态,反映出板块间的碰撞挤压作用力在平行剪切带和垂直剪切带方向上存在应力分解。剪切带内糜棱岩中的锆石U-Pb定年结果显示,其年龄为172~137 Ma,据此得出殷马剪切活动时代主要为中侏罗世—早白垩世。
The ductile shear zone of the Yin-Ma (Yinma) ductile shear zone is an important boundary fault on the southern margin of the Tongbai-Dabie orogenic belt. The study on its fine tectonic deformation will be helpful for further understanding of the Tongbai-Dabie orogen Belt evolution and process. In this paper, two sections of Yindian and Mahuang are studied in detail. Using the finite strain measurement, the average axial rate of the long axis and short axis of the rock strain ellipsoid in the Yinma shear band is calculated to be 1.69, and the rock near the shear band According to the analysis of tectonic stress field, the paleo-stress state of the shear zone is ascertained. The maximum compressive stress σ_1 is north-north east-south-south-west, and the corresponding maximum tensile stress σ_3 is northwest West - South East East. The finite strain analysis and stress field of rock show that there is stress decomposition in the direction of parallel shear band and vertical shear band. U-Pb dating of zircons in the mylonite in the shear zone shows that the age is from 172 to 137 Ma. It is concluded that the period of Yinma shear activity is mainly from Middle Jurassic to Early Cretaceous.