The Geochemical Characteristics Of The Intrusive Rocks In Balagaermuchang Of Xiwuqi,Inner Mongolia,and Their Geological Significance

The paper is based on the previous geological investigations in the area of Balagaermuchang,Xiwuzhumuqinqi,relying on the project"1:50000 Geology and Mineral Resources Regional Survey of Baiyinnuoermuchang in Xiwuzhumuqin,Inner Mongolia Autonomous Region",take a scientific and concrete research of Triassic intrusive rocks in Balagaermuchang.Making a detailed description and analysis in the characteristics of the petrology and the geochemistry,on the syenite-granite and granite-porphyry of Triassic,determining the age of the intrusive rock,discussing their petrogenesis and tectonic environment.The types of the Triassic intrusive rocks are mainly syenite granite in the Early Triassic and granitic porphyry in the Middle Triassic,the previous geological investigations had measured the formation time of intrusive rocks is Jurassic,this study of the zircon U-Pb dating results show that the syenite-granite formed in 239Ma²41Ma,the granite-porphyry formed at 231²37Ma.In the study of the geochemical analysis of the syenite-granite and the granite porphyry,characterized by granite classification diagrams illustrating,displaying having a high potassium,alkaline characteristics,determining the rocks series of Aluminum and SiO₂ are supersaturated,belongs to A-type granites.REE assemblage diagram and trace element spider diagram exhibits LREE enriches,HREE slightly loss,LREE fractionated obviously and has the obvious negative Eu anomaly.Through comparative analysis and finding the intrusive rocks share an homology with the intrusive rocks in wulanwutai,Zr and Hf of the high field strength elements?HFS?increase significantly intrusive granitic porphyry in the Late Triassic.The intrusive rocks of Balagaermuchang has plate edge features,in the Early and Middle Triassic,generated as the result of remelting magma when the ancient oceanic plate subducted deep into the crust,so as to that it belongs to the after-collision granite.At this time orogenic activity has ended,the oceanic plate and is closed with the continental plate,the plate is in the the conversion phase when the plate transformed from closed to stretching configuration,in the orogenic belt of the central Inner Mongolia.At the same time according to the Rb-Sr,it can be deduced that the thickness of subduction zone where the magmas generated is 30km or more,close to the upper mantle,Sr-Yb classification diagram also shows its dive in the thickness of 30km,situated in the low Sr High Yb region which meet the characters of the A-type granites.