The Neoproterozoic Magmatic Event At Mount Emei On The Western Margin Of The Yangtze Block And Its Implications For The Disintegration Of The Rodinia Supercontinent

There are more Neoproterozoic magmatic rocks in the western margin of the Yangtze block,which provide a lot of convincing evidence for the process of Rodinia supercontinent cleavage.The geographical location in this study area is located in Emei Mountain in Sichuan Province,and the tectonic location is located at the southwest edge of Sichuan Basin.The object of this study is Emei Mountain magmatic rock.This paper analyzes the petrology and geochemical characteristics of Emei magmatic rock,determines the formation time of Emei magmatic rock,and discusses the magmatic source nature,tectonic geological background and petrogenesis of Neoproterozoic magmatic rock through the analysis of total rock principal amount and trace elements,zircon U-Pb chronology and zircon in-situ Hf-O isotope characteristics of Emei magmatic rock located at the western edge of Yangtze block.At the same time of genetic analysis of magmatic rocks,the specific time,main mechanism and corresponding movement mode and direction of Rodinia supercontinent cracking are analyzed and explained.The results are of substantial significance for analyzing the tectonic evolution process of the western margin of Yangtze block and the main mechanism and process of Neoproterozoic Rodinia supercontinent cracking.Emeishan magmatic rock consists of two different colors of monzogranite and diabase vein,of which the dating results of the two different types of monzogranite are 818±30Ma and 817±34Ma respectively.Through primary and trace rare earth analysis,the results show that the two types of granite belong to peraluminous type A granite with high potassium and calcium alkalinity,and the major ions are relatively rich in Magma Elemental K,Rb,Sr,Ba,etc.High field strength elements(HFSE)Hf,Ti,Nb,Ta,Th,Eu,etc.are relatively deficient,light rare earth is enriched,heavy rare earth is deficient,light and heavy rare earth are highly differentiated,with negative cerium anomaly and negative europium anomaly,indicating that light rare earth elements have strong internal fractionation and plagioclase crystallization differentiation.It is formed in the tectonic background of crust thinning,after collision(after mountain building)and intraplate tectonic background.The diabase vein has a dating result of 814±43Ma and belongs to K-Ca basic rocks.Large ion Magma Elemental(LILE)K,Rb,Sr,etc.are relatively enriched,while high field strength elements(HFSE)Hf,Ti,Th,Zr,etc.are relatively deficient.They also show light rare earth enrichment and heavy rare earth depletion.The light rare earth and heavy rare earth are highly differentiated,showing a weak positive europium anomaly,indicating that plagioclase does not undergo crystallization differentiation.Formed in rift environment or orogenic belt,the collision has been completed at this time and is in the post-orogenic stretching stage.By comparing the dating results of the Neoproterozoic magmatic rocks on the western-northern margin of the Yangtze block,it is found that their age distribution characteristics are consistent with those of the predecessors for the whole of South China and Australia.Therefore,it is believed that the formation of Emeishan magmatic rocks may be related to the mantle plume activity that caused Rodinia supercontinent cleavage in Neoproterozoic.At the same time,based on the characteristics of granite and basic rocks in different regions,the geodynamic evolution model of South China from the end of Mesoproterozoic to the middle of Neoproterozoic is summarized.