Zircon U-Pb Age Composition Of The Early Cretaceous Mafic Dikes In Jiaodong And Its Geological Significance

In Jiaodong Peninsula,a large number of early Cretaceous mafic dikes rocks are exposed,the study shows that they originate from the deep Mesozoic enriched lithospheric mantle in the Jiaodong Peninsula,and the evolution process and Genesis mechanism of the Jiaodongenriched lithospheric mantle are still full of controversy,There are a lot of zircon andin the mafic dikes rocks of Jiaodong Peninsula,it not only records the Jiaodong-thermal events but also retains many important informations of the lithosphere mantle,which provides an important clue for us to understand the complex tectonic evolution process and crust-mantle interaction in Jiaodong.In this paper,the mafic dikes of Jiaodong is sampled,and the rock facies,zircon U-Pb datingand other related work are carried out,and the following main understandings are obtained:?1?The results of lithofacies study show that the lithology of the Early Cretaceous maficdikes rocks in Jiaodong Peninsula is mainly the lamprophyre and the Porphyrite rocks,and the main mineral compositions are as follows:pyroxene,hornblende,plagioclase and biotite.?2?The main age peaks of zircon age in the Early Cretaceous mafic dikes are².9Ga,².5Ga,².2Ga and¹.85Ga,and the².9Ga age peak is the age record of rapid crustal hyperplasia of the North China Craton;the².5Ga age peak records the magma heat event in the north of the Jiaobei,which mainly shows the ancient crust remelting and a small number of crustal regeneration;the peak age of².2Ga records the magmatic activity around 2200Ma in the Jiaobei area,and the peak age of around1850Ma records the late metamorphic events,which may be associated with the collision orogeny and accompanied by the thickening of the crust.?3?The mafic dikes contain neoproterozoic zircon,the Paleozoic zircon,Triassic metamorphic zircon and ancient zircon,the T_DM2 ages of zircon in magmatic period are both paleoproterozoic ancient age and ancient age,which indicates that there are two kinds of North China continental crust and Yangtze continental crust in the source region of the Early Cretaceous mafic dikes in the Jiaobei.The addition of North China craton crust and Yangtze crust is an important reason for the evolution of the Jiaodong lithosphere mantle to enrichment,and its genesis mechanism may be related to the subduction of Yangtze plate during the Triassic period and the lithospheric mantle sedimentation in the eastern part of the North China Craton.