鄂东南九宫山地区多期构造特征及其对区域大地构造演化的启示

Characteristics and Enlightenment to Regional Tectonic Evolution ofMulti-stage Tectonic in Jiugongshan Area, Southeast Hubei

鄂东南九宫山地区处于扬子地块东南缘与江南造山带交接部位,经历多期构造—岩浆事件,并伴生多期构造形迹。通过对研究区丰富的构造形迹进行综合整理和分析,总结该区晋宁期、加里东期和印支期构造变形及演化特征。研究认为,由于构造变形的区域不均衡性,造成九宫山地区青白口系冷家溪群基底和南华系—志留系沉积盖层的构造变形特征存在显著差异,具体表现为:冷家溪群基底存在新元古代时期早期SN向褶皱被晚期EW向褶皱叠加改造的构造特征,并伴有右行旋扭,形成冷家溪群在图面上的“丰”字型构造体系;而在南华系—志留系沉积盖层中表现为NE-SW向逆冲断层被晚期伸展滑脱构造破坏和改造,岩石以脆性变形为主。总体上反映九宫山地区的变形强度自下而上由强变弱,并由韧性变形转变为脆性变形。

The Jiugongshan area in southeastern Hubei is located at the junction of the southeastern margin of the Yangtze Block and the Jiangnan Orogenic Belt.It has experienced multi-stage tectonic-magma events and is associated with multi-stage structural features.Through the comprehensive arrangement and analysis of the rich structural features in the study area,the structural deformation and evolution characteristics of Jinning Period,Caledonian Period and Indosinian Period in this area are summarized.It is believed that due to the regional imbalance of structural deformation,there are significant differences in the structural deformation characteristics of the basement of the Lengjiaxi Group of the Qingbaikou System and the sedimentary cover of the Nanhua-Silurian System in the Jiugongshan area.The specific performance is as follows:the basement of the Lengjiaxi Group has the structural characteristics of the early SN-trending folds superimposed by the late EW-trending folds in Neoproterozoic,accompanied by dextral twist,resulting in the unlque“Feng”font structural system characteristics of the Lengjiaxi Group on the map;in the Nanhua-Silurian sedimentary cover,the NE-SW thrust fault is destroyed and reformed by the late extensional detachment structure,and the rock is mainly brittle deformation.In general,the deformation intensity of Jiugongshan area in southeastern Hubei Province changes from strong to weak from bottom to top,and from ductile deformation to brittle deformation.