Zircon U-Pb Geochronology,Geochemistry And Its Geological Implication For The Neoarchean Rocks Of Zhongtiaoshan Area In Southern North China Craton

The basement time of the North China Craton and the tectonic and evolution process of the Craton is one of the important issues of the NCC Precambrian geological research.The Zhongtiaoshan area is located on the southern margin of the NCC and has a relatively complete development of the Precambrian basement rock strata.This area develops a large-scale ~ 2.5Ga event,but the main research body is TTG,granite and slanted amphibolite.In this study,the monozogranite and TTG gneiss in the Sushui complex in the northwestern part of Zhongtiao Mountain were selected as the research objects,focusing on the exact age of the formation of the monozogranite and the TTG gneiss in the northern section of the Zhongtiao Mountain,and on this basis combining the petrology,geochemistry,zircon U-Pb chronology and Lu-Hf isotope study to determine the genesis and environment of each rock,so as to the geological events of the early Precambrian period and its significance is explored.Based on the study of the Sushui complex and its southern Taihua complex and Dengfeng complex,the significance of the ca.2.5Ga geological event in the southern margin of the North China Craton is discussed.This study has mainly achieved the following points:(1)The one-stage tectonic thermal event in the Zhongtiaoshan area was determined,that is,the monozogranite formed at 2533±16 Ma;petrology,geochemical characteristics and zircon Hf isotopic composition indicate that the rock belongs to high potassium calc-alkaline The series may be formed by partial melting of the 2.7~2.9Ga mafic lower crustal material.In addition,the zircon edge age information reflects the occurrence of a tectonicthermal event in the region at about 2200 Ma.(2)The formation age,rock genesis,source area properties and tectonic setting of the TTG rock in the area along the Jixian in the northern part of Zhongtiao Mountain were investigated.The zircon U-Pb dating result of the rock is 2513±16 Ma,indicating that it was formed in the late Neoarchean.The results of petrology and geochemistry show that the rockmass is a series of calcium-alkaline,and the source material mainly comes from the underplating caused by partial melting of the depleted mantle,which in turn induces partial melting of the mafic magma.(3)The Zhongtiao area ~2.5Ga TTG rock and the monozogranite together indicate that the North China block has been basically cranicized at the end of the Neoarchean.(4)On the basis of the above work,through the study on the formation age of the Sushui complex in the Zhongtiaoshan area and the Lushan,Xiaoqinling Taihua complex and Dengfeng complex,the geological events of the North China Craton ca.2.5Ga are summarized and analyze its meaning.