准噶尔西北缘石炭-二叠纪构造转换期变形分析及其地质意义

Deformation Analyses and Their Geological Implications of Carboniferous-Permian Tectonic Transformation Period in Northwest Margin of Junggar Basin

通过对扎伊尔山至哈拉阿拉特山一带详细的构造变形分析,揭示出准噶尔西北缘主要发育以下3组构造组合:近南北向、北东-南西向和近东西向.其变形序列为:晚石炭世早期,发育近南北向褶皱-冲断构造;晚石炭世时期,近南北向构造线受牵引拖拽呈北东-南西向,达尔布特、克拉玛依蛇绿混杂岩以右旋走滑拉出或侧向楔冲形式构造就位于上覆石炭系中;晚石炭世晚期至二叠纪,发育以达尔布特断裂为代表的北东-南西向伸展断裂,伴随广泛的中基性岩脉及花岗岩侵入;二叠纪末至三叠纪初,发育广泛的近东西向劈理、哈山一带逆冲推覆构造及达尔布特左旋走滑活动.石炭纪至二叠纪,西准地区经历了从俯冲到碰撞再到碰撞后陆内变形的演化过程,伴随着挤压和伸展多期构造叠加,充分体现了该地区复杂构造转换变形的动力学过程.

Detailed deformation analyses of the Zaire-Hala＇alate Mountains show the following three different directional trends of regional structural features developed in the northwest margin of the Junggar basin：the south-north（S-N）,northeast to southwest（NE-SW）and east-west（E-W）directions.The deformation sequences demonstrate that nearly S-N fold-thrust structures were developed during the early Late Carboniferous.During the late Late Carboniferous,nearly S-N tectonic orientation was transformed into the NE-SW direction by dragging.Meanwhile,the Darbut and Karamay ophiolitic mélanges were emplaced into the overlying Carboniferous strata by pulling-out under the control of dextral strike slip shearing or lateral wedge extrusion.Subsequently,NE-SW extensional faults,represented by the Darbut fault,were developed during the late Late Carboniferous to Permian,accompanied by extensive intrusion of intermediate to mafic dykes and granites.Between the end Permian and the Early Triassic,widespread E-W cleavages and thrust nappes in the Hala＇alate Mountains were developed,and theDarbut sinistral strike slip fault was activated.From the Carboniferous to the Permian,the western Junggar underwent complicated evolutional processes including subduction,collision and intra-continental deformation,with multiphase tectonic overprints of compression and extension.The tectonic evolution history in the study area fully exhibits the regional geodynamic processes in the tectonic transformation deformation.