黔中隆起性质及其构造演化

Characteristics and tectonic evolution of Qianzhong Uplift

"黔中隆起"是雏形于晚寒武世郁南运动的东西向平缓隆起,经历了都匀运动水下隆起向陆上隆起的转化发展阶段。通过对比沉积岩相与古地理研究,黔中隆起水陆转换开始于晚奥陶世涧草沟期,即都匀运动发生的时间,鼎盛时期发育在晚奥陶世五峰期至早志留世龙马溪期。广西运动期间,受到来自南部云开地块与桂滇-北越地块的挤压和南东向华夏地块与扬子板块汇聚、碰撞脉动式收缩的远程效应,出现了以黔中背斜、乌当-二比向斜为代表的东西向构造带和以麻江背斜为代表的南北向构造带共存的现象,之后,"黔中隆起"作为独立意义的构造单元消失,与"江南古陆"相连接进入联合发展时期。东吴运动和峨眉山玄武岩的喷发改变了黔中隆起控制东西走向的沉积古地理格架,变为近南北向,黔中隆起与上扬子地区的构造演化彻底融为一体,标志黔中隆起演化的彻底结束。黔中隆起南缘边界的镇远—贵阳断裂中的钾镁煌斑岩单颗粒锆石U-Pb同位素年龄为(261.3±8.0)Ma,很好地指示了黔中隆起作为独立单元发展的最后年限。

Qianzhong Uplift,an E-W gentle uplift,formed in the Late Cambrian period under the control of the Yu＇nan movement.Its evolution went through a transformation stage from underwater to land uprisings,and the Duyun movement caused the transformation between the two uprising stages.The comparison of the sedimentary lithofacies and paleogeography shows that the transformation began in the Late Ordovician Jiancaogou sedimentary stage,at the time of the occurrence of Duyun movement,and its peak developed from the Late Ordovician Wufeng stage to the Early Silurian Longmaxi stage.During the Guangxi movement,Qianzhong Uplift was compressed by Yunnan-Guizhou-North Vietnam land mass from south to north and by the remote effect caused by convergence and collision between Cathaysia block and Yangtze plate from south-east,which caused the two types of geological structures survived simultaneously in Qianzhong Uplift and its surrounding areas.They are the E-W structures represented by Qianzhong anticline and Wudang-Erbi syncline,and the S-N structure represented by Majiang anticline,respectively.Then,the Qianzhong Uplift as an independent tectonic unit disappeared.It connected into a joint development period with the ＂Jiangnan ancient land＂.The Dongwu movement and the Emeishan basalt eruption changed the E-W trending paleogeographic frame of the deposition under the control of Qianzhong Uplift to nearly north-south pattern of sedimentary paleogeography.Thereby the tectonic evolution of Qianzhong Uplift was completely integrated with the Upper Yangtze region,indicating an end to the evolution of Qianzhong Uplift.The zircon U-Pb age of lamproite in the southern edge of the boundary Zhenyuan-Guiyang fault in Qianzhong Uplift is 261.3±8.0 Ma,which is a good indicator of the ending time of the Qianzhong Uplift being an independent unit.