Study On The Rock Mass Deformation And Geological Significance Of The Southwest Margin Of Yangtze Platform Neoproterozoic Magmatic Complex Structure

In the southwest margin of the Yangtze platform,From Sichuan Kangding,Shimian,Guomianning,Dechang and Miyi to the Yunnan Yuanmou area,there are a large number of Mesoproterozoic rocks and basic,medium-basic,acidic rock are distributed.According to its geographical location,it can be divided into Kangding magmatic complex,Shimian magmatic complex,Mianning magmatic complex,Miyi magma complex and Yuanmao magma complex.The Previous chronological data indicates that these complex rocks are formed in Neoproterozoic.We have had zircon age tested for the Mianning mausoleum in the southwest of Yangzi platform in this paper,and the test data shows that the age of diorite in Mianning complex is 747±20Ma,the age of gabbro is 758±6Ma,the age of granite is 729±26Ma.They are all Neoproterozoic products.At present day,the background of the formation of this Neoproterozoic magmatic complex has different viewpoints,such as the the mantle plume causing viewpoint,plate subduction properties of the island arc causing viewpoint.These studies are based on geochemistry and petrology,and they lack of analysis of the Neoproterozoic magmatic complex structure in the southwestern margin of the Yangtze platform,especially the native structure of these rocks,such as the surface Measurement,etc.,which has important significance for the understanding of the formation of these rock stress environment,and the representative of the tectonic background.In this paper,the methods of field research,microscopic tectonic analysis and magmatic primary surface measurement were used to study the surface and line formed in these magmatic rock mass bodies in this paper.It is found that there are a lot of the magmatic flow floliation developed in the southwest of the Yangtze platform,The directions include northeast,northwest and northwest.At the same time,a ductile shear zone is developed in the southwest margin of the Yangtze platform,which reflects that the ductile shear zone is formed in the leftward strike-slip tectonic setting.The age of the fading formed by the shear in the mixed rock indicates the formation time of the ductile shear zone is at 757±15 Ma,which limits the formation time of the Mianning ductile shear zone is the late Neoproterozoic.In this paper,The magmatic flow floliation of these rocks show that they are subjected to near east-west squeezing at the time of formation,And the kinematic characteristics of the ductile shear zone show that this compression has a certain sinistral strike slip component,which may reflect the dynamic environment of the oblique subduction collision.