Characteristics And Significance Of Metamorphic Rocks In The Southern Area Of Alax,Inner Mongolia

This paper mainly studies the Precambrian metamorphic rocks in the southern area of Alashan,Inner Mongolia.The metamorphic rocks in the area can be divided into Wulashan group complex and Alax group complex,and Alax group complex can be divided into the Hawula formation group,Zuzongmaodao group complex and Deerhetongte group complex.The metamorphic facies are mainly high greenschist facies-low amphibolite facies,and the metamorphism is dominated by regional metamorphism.The metamorphic rocks underwent three metamorphisms.The first metamorphic facies are amphibolite facies,regional metamorphism,and the second metamorphic facies are high porphyry facies-low amphibolite facies,regional metamorphism,third metamorphic high greenschist facies,regional metamorphism.The Wulashan group complex underwent three metamorphisms.The Hawula group complex underwent the second and third metamorphisms.The Zuzongmaodao group complex underwent the third metamorphisms.The rock types of the Wulashan group complex are amphibolite,Biotite plagio-gneiss,quartz schist,leptynite.The protoliths are sediment-volcanic series.The metamorphic temperature is 500-750 ° C and the pressure is 0.2-0.45 GPa.The rock types of the Hawula group complex are amphibolite,Biotite plagio-gneiss,leptynite.The protolith is a set of metamorphosed supercrust rock series mainly composed of volcanic rocks.The metamorphic temperature is 600~720 ° C and the pressure is 0.5 GPa.The rock types of the Zuzongmaodao group complex are two-mica quartz schist and leptynite.The protolith is a set of volcanic-sediment rocks,and the metamorphic temperature is 480~530 ° C and the pressure is 0.6 GPa.The metamorphic rocks in the study area are compared with the metamorphic rocks of the North China plate in the same period,which reviews that two series of rocks have different metamorphism and protoliths.It is speculated that in the Proterozoic period the metamorphic rocks in this area and rocks in the North China Block should be in different tectonic units.