Reseach Of The Detrital Zircon From Mesoproterozoic Sedimentary Strata In The North Margin Of Yangtze Craton, China

The discovery and research of ancient rocks and continental crust is the main way to probe into the Earth’s formation and evolutionary history. And the Zircon’s U-Pb dating is the primary mean for the discovery of ancient continental crust. Unlike the North China Craton, where Archean rocks are widespread, Precambrian basement rocks of the Yangtze Craton are exposed sporadically due to coverage of thick Sinian and Phanerozoic sedimentary strata. So, Proterozoic strata of Yangtze Craton have been found in Hannan, Wudang, Yunnan axis and Shenlongjia area, expect Kongling area. And Shenlongjia area as an important exposed Precambrian basement located at the northern part of Yangtze Craton. The sandstones from the sediments provide ideal samples for the further studies of age and evolution of Proterozoic Yangtze Craton. This paper is a research on detrital zircon of Shenlongjia area with analysis of Zircon’s age, trace element, Hf isotope and O isotope by LA-ICPMS, LA-MC-ICPMS and SIMS. The age studies of detrital zircons from sedimentary rocks in the Shenlongjia area show major age groups of～1.6Ga,～1.8Ga,～2.0Ga and～2.7Ga with few grains>3.5Ga that indicates the existence of magmatic activities of these ages in Yangtze Craton. A large number of～1.6Ga zircon with positive εHf(t) and ca.5.3%。 δ18O values found in Yangtze Craton suggest the addition of mantle material to continental crust forming juvenile crust. The available evidence indicate that Yangtze Craton separated form the Columbia supercontinent at～1.6Ga. Furthermore, nearly all zircons of age～1.8Ga and～2.0Ga show negative sHf(t) and higher δ18O values indicate the crustal reworking of these two stages.