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鄂尔多斯盆地西缘位于华北陆块和秦祁昆山造山带两个一级大地构造单元之间的过渡带内,特定的大地构造背景使其具有复杂的构造演化历程及特殊的煤田构造格局。鄂尔多斯盆地西缘由贺兰山逆冲推覆构造系统和六盘山东麓逆冲推覆构造系统组成,具有“南北分段、东西分带”的特点。为了进一步探讨鄂尔多斯盆地西缘煤田构造格局的形成演化及区域构造控制因素,本文基于野外地质调查和煤田勘查资料,恢复了本区自晚古生代以来的沉降抬升史和古构造应力场特征。印支期:研究区北部最大主压应力方向为北西-南东向,南部最大主压应力方向为北东-南西向;燕山期:北部最大主压应力方向为北西西-南东东向,南部最大主压应力方向为北东东-南西西向;喜马拉雅山期:北部受北西西-南东东向拉张应力,南部最大主压应力方向为北东-南西向。采用有限元数值模拟,探讨了鄂尔多斯盆地西缘煤田构造格局的形成与区域构造的演化的关系,强调北段贺兰山逆冲推覆构造系统的形成与阿拉善地块的向东挤出逃逸密切相关。
The western margin of the Ordos Basin is located in the transition zone between the two first-grade tectonic units of the North China Block and the Qinqi-Kunshan orogen. The specific tectonic setting has complicated tectonic evolution and special coalfield tectonics. The western Ordos Basin is composed of the Helan Mountain thrust nappe structure system and the thrust nappe structure system of the Liupan Mountains. It has the characteristics of “north-south segment and east-west zone”. In order to further explore the formation and evolution of the tectonic framework and the tectonic controlling factors in the western margin of the Ordos Basin, based on the field geological survey and coal prospecting data, this paper restored the characteristics of the subsidence and uplift history and palaeotectonic stress field since the Late Paleozoic. Indosinian: The direction of the maximum principal compressive stress in the northern part of the study area is northwest-south eastward, the direction of the maximum principal compressive stress in the south is north-east-southwest direction; Yanshanian: the direction of the maximum principal compressive stress in the north is north-west-south-east- The direction of maximum principal compressive stress in the southern part is NE-SW-WNW. In the Himalayan period, the northern part is tension-stressed from NW to NS-NE in the north and NE-NS in the south. The relationship between the formation of coalfield tectonics and the evolution of regional tectonics in the western margin of the Ordos Basin is discussed by means of finite element numerical simulations. It is emphasized that the formation of the Helan Mountain thrust nappe structural system in the northern segment is closely related to the eastward extrusion and escape of the Alxa block .