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狼山群作为阿拉善地块东北部重要的前寒武系地层单元,记录了复杂的构造变形演化历史。本文通过对狼山西南段出露的新元古代狼山群进行构造地质试点填图、剖面测制等方面的研究,总结了狼山群构造变形特征,并对其变形时代和期次进行了初步划分。研究表明狼山群第一期构造变形特征表现为一系列同斜倒转褶皱构造(D1),第二期为近东西向的韧性右行走滑剪切(D2),第三期为北东向巴彦乌拉山—狼山断裂活动对狼山群构造变形进行改造(D3)。结合该地区前人研究成果及年代学资料认为:新元古代狼山群同斜倒转褶皱主要受到古亚洲洋向南俯冲,在古生代晚期沿恩格尔乌缝合带与阿拉善地块北缘拼合,导致近南北向的构造挤压,在狼山地区形成了早期枢纽NEE-EW向的褶皱;晚古生代末期-中生代早期古亚洲洋关闭后发生的板内变形在狼山地区形成韧性右行剪切;三叠纪中晚期韧性左行剪切形成北东向走滑断裂,并使早期形成的褶皱枢纽走向转为北东,奠定了狼山地区现今的构造格局。
Langshan group, as an important Precambrian stratigraphic unit in the northeastern part of Alxa Block, records the history of complicated structural deformation and evolution. Based on the study of the Neoproterozoic wolf hill group exposed in the southwestern Langwon volcanic area by means of structural geological pilot mapping and profile measurement, this paper summarized the tectonic deformation characteristics of the Langshan Group and carried out the deformation epoch and period Preliminary division. The study shows that the first phase of the Wolfshan Group tectonic deformation is characterized by a series of synclinal inversion fold structures (D1), the second phase is near east-west ductile right strike-slip shear (D2), and the third is NNE Reconstruction of Tectonic Deformation of Wolfshan Group in Yanwu - Shan - Langshan Fault Campaign (D3). Based on the previous research results and chronological data of the area, it is concluded that the synoptic reverse fold of the Neoproterozoic Langshan Group was mainly subducted southward by the Paleo-Asian Ocean and merged with the northern margin of the Alxa Block in the late Paleozoic resulting in Near the north-south tectonic extrusion, early NEE-EW folds were formed in the Langshan area. During late Late Paleozoic-Early Mesozoic, intraplate deformation occurred after the closure of the Paleo-Asian Ocean, forming ductile right-lateral shear in the Langshan area. The middle-late Triassic ductile left-lateral shearing resulted in the NE-trending strike-slip faults and the early formation of fold hubs turned to the north-east, laying the present tectonic framework in the Langshan area.