北疆阿巴宫-库尔提断裂带显微组构的运动学和动力学分析

研究了阿尔泰地区NW走向高角度冲断构造中主干的阿巴宫—库尔提断裂带。详细研究了断裂构造岩的变形构造和组构及其所显示的运动学和动力学特征。结果表明:存在早、晚更替且性质不同的变形显微构造。早期以糜棱岩中的韧性变形构造为主,发育有递进变形的不对称构造(压力影、旋转变斑晶、S—C构造等),是断裂中剪切变形运动指向的主要判据。晚期为脆性破裂构造,与早期变形组构具继承、叠加关系。研究了石英光轴的组构形式,证实存在:早期共轴纯剪变形的小圆环带组构和非共轴简单剪切变形中,呈递变关系的点极密—大圆环带—交叉大圆环带组构型式。对变形构造和组构所作的运动学和动力学分析结果表明:阿—库断裂带的形成和变形历史为:①地壳早期NE挤压收缩环境,形成劈理化带;②在持续NE向挤压作用下,大规模剪切、逆冲叠置,和地壳加厚,产生重熔岩浆和流体再分配效应,促使糜棱岩带形成和发展;③晚期地壳NE向挤压下,以垂直差异抬升和大量碎裂岩化高角度逆冲断裂的继承、叠加为特征。在区域大地构造的关系上:①、②对应于地槽褶皱、封闭的地槽体制(海西期),③对应于地洼体制(后海西期)。

KINEMATIC AND DYNAMIC ANALYSES OF MICROSTRUCTURES AND FABRICS OF THE ABAGONGKUERTI FAULT ZONE IN NORTHERN XINJIANG

The Abagong-Kuerti fault zone in Altay area, one of NE-trending high-angle thrusts, has been studied. Deformation microstructures and fabrics of fracture tectonices, and their kinematic and dynamic features have also been investigated in detail. The results suggest that there exists alteration of early and late periods' microstruetures with different deformation natures. Ductile deformation structures in mylonites and asymmetric structures (pressure shadow, ratational porphyroblast, porphroclast system, S-C structure et al.) occur prominently in the early period. These structure are the main kinematic indicators of progressive shear deformation. In the late period, brittle rupture structures inherited and were superimposed on the early deformation fabrics. The research into the optical axes fabrics of quartz shows the small circle girdle fabric resulting from early coaxial pure shere deformation and the progressive relationship of point maximum-large circle girdle-cross large circle girdle resulting from non-coaxial simple shear deformation. The kinematic and dynamic analyses of deformation microstructures and fabric indicate that the development and deformation histories of AKF are as follows: (1) early NE compression and contraction of the earth's crust, resulting in the form of cleavage zones: (2) under the condition of continuous N E compression, large-scale shear and thrust imbrication took place, leading to the thickening of the carth's crust, the production of re-melting magma, re-distribution effect of fluids, and the production and development of mylonite zones: (3) under the NE compression of the crust in the late period, the regional geology is characterized by vertical differential movement and inheritance and superimposition of cataclastic high-angle thrust faults. In regional tectonic sensc. (1) and (2) correspond to a geosynclinal regime with geosynclinal folding and closing (Hercynian), while (3) corresponds to a diwa regime (epi-Hercynian).