Crustal growth of the Yanliao intracontinental rift basement——insights from U-Pb ages and Lu—Hf isotopes of the detrital zircon from Mesoproterozoic Changcheng System
Objectives:The North China Craton stands as one of the most ancient cratons worldwide,with its continental crust undergoing multiple episodes of crustal growth events.Considerable research has been conducted on the growth of the continental crust in the North China Craton.However,previous discussions on the crustal growth of basement beneath the Yanliao Rift Basin,obscured by extensive deposits of thick sedimentary cover,have been relatively scarce.Methods:Taking the sedimentary rocks of the Mesoproterozoic Changcheng System above the basement of the Yanliao Rift Basin as example,this study systematically analyzes the detrital zircon age spectra and Lu-Hf isotope data from the Changcheng System strata within the Yanliao Rift Basin.The investigation aims to elucidate scientific inquiries concerning the sedimentary age of the Changcheng Formation,the provenance of detrital zircons and crustal growth events.Results:The isotopic ages constrain the sedimentary age of the Changcheng System in the Yanliao Rift Basin as ca.1680 Ma,which represent the timing of initiation of the Yanliao Rift.The detrital zircon age spectrum from the Changcheng System in the Yanliao Rift Basin primarily exhibits two stages:2.7～2.5 Ga and 2.2～1.9 Ga.The Hf isotope εHf(t) values manifest in a high positive range of 0.1 to 34.6.By comparing the detrital zircon U-Pb dating,Lu-Hf isotope εHf(t),and TDM2 model age data of the Changcheng System with the crystalline basement of the North China Craton,it is inferred that the sediment source of the Changcheng System in the Yanliao Rift Basin is the underlying basement of the Yanliao Rift Basin.Conclusions:① The detrital zircon age spectrum of the Changcheng System in the Yanliao Rift Basin defines two major age populations two main stages:2.7～2.5 Ga and 2.2～1.9 Ga.The Hf isotope εHf(t) values exhibit a high positive range between 0.1 and 34.6.② Combining zircon U-Pb dating,zircon Lu-Hf isotope εHf(t) and TDM2 model age,it is suggested that there are three distinct episodes of crustal growth in the Yanliao Rift Basin of the North China Craton during the Neoarchean to Paleoproterozoic Eras,occurring at 2.7～2.5 Ga,2.2～1.9 Ga,and 1.7～1.6 Ga.
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