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中蒙边界的亚干地区经历古生代造山作用之后,中生代经历两次重大的构造事件:造山期(晚三叠-早侏罗世)为地壳的缩短导致总体向南的特大型推覆构造;晚造山期(晚侏罗-早白垩世)近南北的地壳伸展,形成变质核杂岩.经构造的运动学和动力学分析查明,造山期形成的推覆构造上盘总体运动方向约180°,运动学涡度约为?0.10,属缩短-增厚型剪切作用,最大主压应力轴方向近水平.晚造山期伸展作用形成拆离断层,上盘总体运动方向约165°:早期运动学涡度平均为0.74,属简单剪切为主减薄型剪切作用,最大主压应力轴倾角66°;晚期伸展作用的运动学涡度为平均0.55,属纯剪切为主减薄型剪切作用,最大主压应力轴方向近直立.表明推覆构造导致地壳的增厚,原处于地壳上层的岩石下沉进入韧脆性转化带以下的下地壳,增温的下盘岩石和其下部分重熔的物质因其体积的增大和比重的减小而上浮,而上盘岩石则因构造增厚负荷加大.在上方负荷和下部热隆的联合作用下,夹持其间的韧性剪切带中的垂向纯剪切组分增大.当垂向纯剪切组分超过简单剪切组分时,韧性剪切带转化为伸展-减薄型剪切带.这一递进转化过程体现了推覆构造和伸展构造时空关系和其间运动学和动力学内在的本质联系:推覆构造引起地壳增厚的过程中孕育了伸展的因素,伸展组分的递增最终导致
After the Paleozoic orogeny of the Sino-Mongolian border, the Mesozoic experienced two major tectonic events: the orogenic period (Late Triassic-Early Jurassic) resulted in the general southward super-large nappe structure due to the shortening of the crust; During orogeny (late Jurassic-Early Cretaceous) crustal extension near the north and south to form metamorphic core complex.According to the kinematic and kinetic analysis of the structure, it is found that the total movement direction of the upper plate of the nappe structure during the orogeny is about 180 ° , The kinematic vorticity is about 0.10, belonging to shortening-thickened shearing and the direction of the maximum principal compressive stress axis is near horizontal. Late detachment faulting forms detachment faults, and the general movement direction of the upper disc is about 165 °: the early movement The average vorticity is 0.74, which belongs to the simple shear-thinning shear thinning and the maximum principal compressive stress axis dip angle of 66 °. The kinematic vorticity of late extension is 0.55, Which indicates that the direction of the maximum principal compressive stress axis is nearly upright, indicating that the nappe structure caused the thickening of the crust. The original crust in the upper crust subsidence into the lower crust below the ductile-brittle transformation zone. The warming lower crustal rock and its lower part Melting material due to its volume increase and proportion Decreases and floats, while the overlying rocks increase due to structural thickening.With the combined effect of the upper load and the lower part of the thermo-drag, the vertical pure shear components in the ductile shear zone sandwiched between them increase. When the vertically pure shear component exceeds the simple shear component, the ductile shear zone transforms into an extensional-thinning shear zone, a progressive process that reflects the temporal and spatial relationships between nappe structures and extensional structures and the kinematics Inherently linked to kinetics: Factors that cause stretching in the thickening of the crust caused by the nappe structure, which in the end result in an increase in the spreading component