Paleoproterozoic events in the North China Craton.
ZHAI MingGuo PENG Peng Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China
This paper deals with several key issues including Paleoproterozoic sedimentary sequences,metamorphism and magmatic intrusion,and comes to following primary suggestions for Proterozoic tectonic evolution of the North China Craton(NCC):(1)The NCC fundamentally amalgamated by continent-continent,arc-continent or arc-arc collisions by～2500 Ma;The NCC behaved as a stable continent block without tectonic-thermal action during 2500～2300 Ma.(2)2300～1950 Ma mobile belts,such as Jinyüand Jiaoliao,formed and represent intracratonic orogenesis with Phanerozoic orogenic characteristics on some aspects.(3)The evolution of these mobile belts includes basin rifting,subduction and final collision at～1850 Ma.(4)A proposed northern mobile belt that was not preserved was located north of the Baiyan Obo.The khondalite sequences possibly represent a structural zone within craton,which was related to subduction and collision of the northern mobile belt and caused deep-level granulite facies rocks to uplift by sole- thrusting.(5)The Baiya Obo,Zhaertai and Huade sedimentary sequences deposed in passive continent marginal basins in 1800～1700 Ma,same as the Changcheng System.(6)The tectonic regime in the NCC was inverted from compression to extension in 1850～1700 Ma,resulting in rifting within craton,mafic dyke swarm emplacing and cratonic basement uplifting.(7)In the middle of northern margin of the NCC,an ultra-high-temperature metamorphic complex has been discovered.The paper also discusses genetic relationship between the ultra-high-temperature metamorphic rocks and high-pressure granulites in the central NCC,and suggests that they are related to a mantle upwelling and magma underplating event of～1900 Ma.