Initial decratonization of the eastern North China Craton: New constraints from geochronology, geochemistry, and Hf isotopic compositions of Mesozoic igneous rocks in the Qingchengzi district.

Herein, new zircon U–Pb ages, whole‐rock major and trace element geochemistry, and Hf isotopes are presented for four Mesozoic granitic rock samples within the Qingchengzi district, eastern China. These data provide precise age and petrogenesis information with respect to the Mesozoic intrusions in the Qingchengzi district, which further constrain the initial decratonization process of the eastern North China Craton (NCC). The zircon U–Pb data reveal that these granitoids are emplaced in the following two stages: Triassic (243–220 Ma) and Middle Jurassic (∼164 Ma). These Mesozoic rocks (lithology: syenogranite, monzogranite, and biotite granite) contain high concentrations of silica (68.94–77.07 wt.%) and total alkali (7.35–9.71 wt.%) together with low concentrations of MgO (0.07–0.98 wt.%), total Fe2O3 (0.81–2.92 wt.%), and CaO (0.17–1.80 wt.%), and they are characterized by an enrichment of large‐ion lithophile elements (LILEs; e.g., Rb, Cs, and K) and light rare earth elements (LREEs) in addition to depletion of high‐field‐strength elements (HFSEs; e.g., Nb, Ta, and Ti) and heavy rare earth elements (HREEs), indicating that these Mesozoic rocks are similar to I‐type granitoids. The εHf(t) values of the magmatic zircons in these granitoids range from −18.7 to −11.4. Such geochemical characteristics indicate that these granitoid formations were generated by the partial melting of the ancient lower crustal material. However, the occurrence of mafic microgranular enclaves in the Shuangdinggou monzogranite implies the mixing of the mantle‐derived magmas. Combined with the results of the previous research, these new data indicate that initial decratonization of the eastern NCC occurred during the Triassic period in response to the collision and amalgamation of the Yangtze Craton and NCC. During the Jurassic, the dynamic mechanism of lithospheric thinning was overprinted owing to the subduction of the Paleo‐Pacific Plate. Furthermore, cratonic destruction reached its peak during the Early Cretaceous, which could be related to the asthenospheric upwelling induced by the rollback of the subducting oceanic slab. [ABSTRACT FROM AUTHOR]