祁阳山字型构造质疑  

QUERY OF QIYANG Ε-TYPE TECTONIC SYSTEM IN HUNAN

作　　者：柏道远[1] 李建清 周柯军 马铁球 王先辉 

机构地区：[1]中国地质大学(武汉)地球科学学院,湖北武汉430074 [2]湖南省地质调查院,湖南湘潭411100

出　　处：《大地构造与成矿学》2008年第3期265-275,共11页Geotectonica et Metallogenia

基　　金：中国地质调查局地质大调查项目(编号200213000035)资助

摘　　要：结合区域构造演化背景及构造变形特征,对祁阳弧形构造的形成机制进行研究。分析表明,传统山字型构造机制难以解释祁阳弧形构造的诸多特征,且前人认为变形动力来源于东西向挤压应力场,也与印支期区域构造应力场实为NWW向的构造背景不符,因此祁阳弧形构造并不属典型山字型构造。基于研究区构造活动的客观实际,提出祁阳弧形构造的可能形成机制:NW向基底隐伏断裂和NNE-NE向主干断裂分别于印支期和燕山期产生强烈左旋走滑活动,从而使区域NNE向构造线在中段产生左旋偏转成为NNW向,从而形成S形的祁阳弧形构造。这一机制可较好解释祁阳弧形构造的若干特征,如关帝庙穹窿呈NWW走向、北反射弧构造形迹不显著、北弧弧顶脱位及内弧曲率大于外弧、南弧弧顶脱位、紫云-中田-高峰串珠状穹窿的形成等。上述认识对华南地区弧形构造研究具有一定启示意义:除山字型构造作用和砥柱作用外,还应注意断裂走滑等其他构造活动对弧形构造的制约,以及多次构造活动叠加对构造形迹可能造成的影响。This paper studied the forming mechanisms of the Qiyang arcuate structure through regional tectonic evolutional setting and characteristics of structural deformations. The study showed that the traditional ε-type tectonic mechanism can not explain some characteristics of the Qiyang arcuate structure, and the previous knowledge viewing EW compressional stress as dynamics source is discrepancy with actual Indosinian NWW compressional stress. Thus the Qiyang arcuate structure is not a typical ε-type tectonic system. According to the features of tectonic movements, the authors bring forward an idea of the possible forming mechanisms of the Qiyang arcuate structure as follows： The intensive sinistral strike-slip motions of Indosinian NW-trending basement cryptic faults and Yanshanian NNE to NE-trending faults caused the regional NNE-trending lineament in the middle segment of the Qiyang arcuate structure to rotate counter-clockwise towards NNE, thus brought about the S-shaped Qiyang arcuate structure. This mechanism can explain several characteristics of the Qiyang arcuate structure, such as the NWW-tren- ding Guandimiao dome, its north reflexarc is absent, the arc-tips of both north arc and south arc are staggered and that the interior part of north are＇s curvature is bigger than the outside, and the forming of the Ziyun-Zhongtian- Gaofeng string of bead domes. The recognitions provide enlightenments to the research of forming mechanisms of arcuate structures in South China： Beside of ε-type tectonic and rubstone-mechanism, investigators should pay attention to the restriction of fault strike-slip motion and other tectonic movements in the forming of arcuate structures, and the impact of tectonic movement superpositions to structural features.

关 键 词：祁阳弧形构造 山字型质疑 断裂走滑 湖南 

分 类 号：P542[天文地球—构造地质学]