Study Of Precambrian Tectonic Deformation In Helan Mountain

Helan Mountain is located in the north of the north-south tectonic belt,adjacent to the Ordos basin in the east and north of the Ordos basin,north of the Alashan block,south of the corridor transition zone,the overall North-North east show.Because of its special tectonic location,it is an ideal place for geologists to study tectonic deformation,magmatic activity,and metamorphism.Based on the analysis of outcrop tectonics,combined with regional tectonics and microstructure analysis,the tectonic deformation of the Precambrian geological body is studied in detail,and the tectonic deformation sequence is reconstructed by using the Precambrian system in Helan Mountain area as the research object.And the development and evolution of Helan Mountain area were discussed in depth.I achieved the following main conclusions:(1)The early Cambrian tectonic activity in the northern section of Helan Mountain has many characteristics,D1 is solid rheological and bedding ductile shear deformation,mainly solid rheological folds and bedding ductile shear zone.D2 is a regional right-right sliding shear shear deformation,which is the most important tectonic trace of the Precambrian in the northern section of Helan Mountain,and the ductile shear deformation is pointed out.D3 is the northwest-south-east to high-angle thrust and ductile shear deformation,which is characterized by ubiquitous,sparsely developed and small-scale ductile shear zone,which is from the south-west to north-east angle.D4 is the extension of the tensile structure deformation,ductile deformation,eye-catching is the structure of diabase emplacement.D5 is from the northeast to the south of the thrust of the role of thrust,fault branching complex,the rock was cut into different sizes of diamond-shaped block.Common quartz veins penetrate through the cross-section,and in the local occurrence of film and fold,reflecting the characteristics of progressive deformation.D6 is a conjugate shear structure deformation,the performance of the two groups of nearly parallel production of dense and penetrating strong cleavage zone,near the upright,is the study area of the latest structural deformation,is the main factor shaping the current landscape;(2)The above-mentioned deformation effects correspond to different temperature and pressure conditions.During the process of regional right-strike-slip shear ductile deformation(D2),the quartz polycrystalline strip and the quartz crystal have long rectangular shape,and the feldspar sub-particles are recrystallized and the recrystallization is inlaid,which reflects the high amphibolite facies-(D3)stage,the fine granulation of mineral particles,the twin crystal of the developmental machinery,the structure of the mantle,the recrystallization of the sub-particles,and the microscopic stratification of the granulite facies.(D4)in the process of extensional tensile tectonic deformation(D4),the phenomenon of brittle-ductile crushing,swelling and recrystallization and so on,Phase deformation and metamorphic environment;(3)Identified in the six tectonic deformation,The second stage(D2)regional right and left sliding shear shear deformation time before and after 2.0Ga;The third stage(D3)is about 400Ma in the northwest-south-east direction.The time of deformation of the fourth stage(D4)is about 200Ma;170Ma may be the beginning of the fifth(D5)thrust nappe,and continue until the new generation;The last deformation of the study area(D6)occurred in the new generation,about 20Ma since.