川北松潘—甘孜盆地东缘晚三叠世物源与秦岭隆升OA

Defining the tectonic attributes and provenance system transformation of the eastern margin of the Songpan-Ganzi Basin during the Late Triassic is the key to understanding the evolution of the Qinling-Songpan tectonic belt.In this study,detrital zircon U-Pb dating and geochemical analysis were carried out on clastic rocks of the Xinduqiao For-mation in the Niong area of Songpan County,eastern margin of the Songpan-Ganzi Basin,to constrain its provenance and tectonic setting.The detrital zircon U-Pb age spectra mainly show four age peaks at 2,466 Ma,1,886 Ma,924-809 Ma and 435 Ma,which comprehensively indicate that the provenance is a multi-source mixture of the southern mar-gin of the North China Block,the North Qinling Orogenic Belt and the ancient basement of the northern margin of the Yangtze Block.Geochemical data further reveal that the provenance is dominated by upper crustal felsic rocks,and the sediments were deposited in a tectonic setting combining a continental island arc and an active continental margin.The weighted mean age of the youngest zircons population(287±5)Ma,together with the absence of Permian to Triassic detrital records,indicates that the North Qinling Orogenic Belt had undergone significant uplift and become a sedimen-tary barrier during the Late Triassic.This study reveals the complex process of multi-directional provenance convergence in the eastern margin of the Songpan-Ganzi Basin during the Late Triassic,and provides key chronological and geo-chemical constraints for reconstructing the coupling evolution mechanism of the basin-orogen system during this period.