Constraints Of Metamorphic Volcanic Rocks Of Interlayer In The Fengzhen Area,Inner Mongolia,to The Formation Time Of The Khondalite Series

The North China Craton is one of the oldest continents on Earth,and its formation and evolution have always been the important research issue.The Khondalite series exposed along the north margin of the North China Craton is mainly composed of marble and meta-sedimentary rocks.The genesis of Khondalite series is thus an key point towards to better understand the formation and evolution of the North China Craton.A class of volcanic rocks transformed by amphibolite-granulite facies are found in the Khondalite series in the Fengzhen area Inner Mongolia.Through the measured section of the Ji Ning Group in Shangyingzi,Fengzhen area,the Khondalite series and the metamorphic volcanic rocks are as to an integrated contact relationship.The metamorphic volcanic rocks were restored by the geochemical analysis,and LA-ICP-MS zircon U-Pb isotopic data suggested that the metamorphic volcanic rocks formed during 1831-1795 Ma,and the metamorphic age is suggested as ca 1780 Ma.The original rocks deposition age of the Khondalite series in the Fengzhen area are limited in ca 1795 Ma,and metamorphosed age around 1780 Ma.Based on the new findings of metamorphic volcanic interlayers in the Khondalite series of the Fengzhen area,together with previous studies on the geochronological,petrological and metamorphic characteristics of the Khondalite series,we carry out the systematically discussed on the deposit and metamorphism eras of the original rocks of Khondalite series and further explored the process of the formation and evolution of the North China Craton.Therefore,this study suggest that the original rock of the Khondalite series in the Fengzhen area may be divided into two stages.Through systematic research,this paper suggests that the western Block is probably is formed by the collision between Ordos block and Yinshan block at ?2.3 Ga,and then a basin is formed in the northern margin of the Ordos block.The original rocks of the Khondalite series deposited in this basin at ?2.0 Ga.The collision between south block and the northern Siberia Craton occurred at 2.0-1.92 Ga,and the peak of the collision event was at ca 1.95 Ga.After that,the extension occurred after collision at 1.92 Ga-1.85 Ga,and ultra-high temperature granulite and S-type granite were formed.The collision between the east block and the west occurred in 1.85 Ga,and then form a Central North China.In the meantime,a foreland basin developed in the eastern margin of the western Block.At this time,the North China Craton was welding together.The original rocks of the late Khondalite series deposited in which basin.The Columbia supercontinent breakup caused the metamorphism of the original rocks of the late Khondalite series in the Central North China in the 1.78 Ga,forming the Khondalite series.