昭通-鲁甸断褶带南段构造变形序列与应力分析

Tectonic Deformation Sequences and Stress Analysis in the Southern Segment of the Zhaotong-Ludian Fault Folding Zone

昭通-鲁甸断裂作为大凉山次级活动块体与华南地块的边界断裂之一,自鲁甸Ms6.5地震以来,备受关注。研究区内昭通-鲁甸断褶带是由NE、NW向断裂和破褶皱共同组成的似花状构造带,为了更加全面、深入了解昭通-鲁甸断褶带,在布设的4个观测区内,基于野外特征与应力分析,初步建立了6个构造变形序列,将其构造演化划分为6个阶段:(1)燕山中期NE、近SN向褶皱形成阶段;(2)燕山中期昭通-鲁甸NE向断褶带形成阶段;(3)燕山晚期NE向断裂反转阶段;(4)燕山晚期EW向叠加褶皱阶段;(5)燕山晚期昭通-鲁甸断褶带伸展阶段;(6)第四纪昭通-鲁甸断褶带活动阶段。为燕山期以后川滇地块与华南地块的运动研究提供了重要的地质依据,并认为昭通-鲁甸断裂晚更新世-全新世构造变形使NE向和NW向断裂均有活动,组成了共轭断裂样式。鲁甸地震的发生与NE、NW向断裂活动均有关。

The Zhaotong-Ludian fault as one of the boundary faults of the Daliangshan secondary active block and the South China block,since the Ludian Ms6. 5 earthquake,this fault was brought into sharp focus. The Zhaotong-Ludian fault zone in the research area is a flower-like structural belt combined with NE and NW trending faultfold zone. In order to have a more comprehensive and deeper understanding of Zhaotong-Ludian fault-fold zone,four particular structural observeing areas was laid out,base on the tectonic deformation sequences,six tectonic evolution stages were established.(1)The NE and near SN fold formation stage in the middle Yansha period.(2)The formation stage of Zhaotong-Ludian fault-fold zone in the middle stage of Yansha period.(3)The Inversion of NEtrending fault-fold zone in Late Yansha period.(4)The EW cross fold stage of late Yansha period.(5)Late Yansha period,the Zhaotong-Ludian fault-fold zone stretching stage.(6)The Quaternary period,the Zhaotong-Ludian faultfold zone activity stage. Over all,an important geological basis for the kinematics study of the Sichuan-Yunnan block and the South China block after Yanshan period were provided. Late-Pleistocene-Holocene tectonic deformation of the Zhaotong-Ludian fault resulted in both NE and NW faults. So that it formed conjugated faults. And the Ludian earthquake is related to NE and NW trending faults.