Abstract: The Shouwangfen complex is composed of biotite quartz diorite and quartz monzonite. Our LA-ICP-MS zircon U-Pb chronological study shows the quartz diorite and quartz monzonite ages are 128±1 Ma, suggesting the Shouwangfen complex formed in the Early Cretaceous, closely coincides with the period of large-scale magmatic activity in the eastern North China Craton. The Shouwangfen complex belongs to the quasi-aluminous rock of alkaline series (A/CNK ranged 0.690.89, A/NK ranged 1.191.35, Na2O+K2O ranged 8.48%9.06% and K2O ranged 3.874.96%), enriched in Rb, Ba and Sr and depleted in Nb, Ta, Th and P. It has the characteristics of high Sr ((6841018)×10-6) and Ba ((11631506)×10-6) contents, high Sr/Y(43102) and La/Yb (3191) values, low Y ((7.1916.55)×10-6) and Yb ((0.471.28)×10-6) contents, enrichment of light rare-earth element (LREE), and no Eu anomalies. The quartz diorite and quartz monzonite have low εHf(t) values of -18.1 to -11.1 and -18.6 to -13.2, respectively. Geochemical characteristics indicate the Shouwangfen complex formed under the tectonic setting of extension environment created by the ancient Pacific plate subduction to the Eurasian continent. The complex originated from the partial melting of Paleoproterozoic crustal material with varying contributions from enriched mantle. The high Sr/Y value, however, is not a source feature due to its positive correlation with SiO2, but a result of fractionation during emplacement.

Key words: high Sr/Y value, zircon U-Pb chronology, geochemistry, Yanshan region, Shouwangfen complex