We report U-Pb dating of zircon,as well as geochemical and Hf isotope data,in order to constrain the formation time,magma source,and tectonic setting of granite porphyry dykes in the Xicha gold-(silver) district in southern Jilin Province,Northeast China.The zircon grains are euhedral-subhedral,display oscillatory growth zoning and have Th/U ratios varying between 0.11 and 0.78,which together imply a magmatic origin.The dating results indicate the porphyry formed in the Early Cretaceous (122 ± 1 Ma),and it contains SiO2 =70.64-72.31 wt％,Al2O3-=13.99-14.64 wt％,K2O + Na2O =6.96-7.81 wt％,K2O/Na2O =1,24-2.10,and A/CNK =1.11-1.41.Chemically,the porphyry belongs to a high-K calc-alkaline S-type granite.Chondrite-normalized rare earth elements (REE)patterns show LREE enrichment,light rare earth elements (LREE)/heavy rare earth elements (HREE) =9.93-11.97,(La/Yb)rN=11.08-15.16,and δEu =0.69-0.95.On the trace element spider diagram,large ion lithophile elements such as Rb,Ba,K,Th,and U are enriched,whereas the high field strength elements Ti and P are depleted.The εHf(t) values of zircon from the granite porphyry vary between-17.1 and-13.2,and their Hf two-stage model ages vary from 2.01 to 2.26 Ga,implying that the magma was derived from partial melting of old lower crust.The granite porphyry dykes and many A-type granites in the region formed at the same time,suggesting an extensional environment.The combination of the occurrence of strong magmatism,large-scale mineralization,and extensional tectonics throughout much of Eastern China indicate that the Early Cretaceous was a period of significant lithospheric thinning.The southern Jilin Province,therefore,experienced lithospheric thinning during the Early Cretaceous.