This paper reports new zircon LA–ICP–MS U–Pb and Hf isotope data, and whole-rock major and trace element data for Late Permian to Early Triassic intrusive rocks in the Yanbian area, NE China. These data provide new insights into the timing of the final subduction of the Paleo-Asian Ocean beneath the North China Craton. The zircon U–Pb age data indicate that a suite of Late Permian to Early Triassic intrusive rocks related to subduction is present within the Yanbian area. The Late Permian intrusive rocks consist of diorites while the Early Triassic granites and hornblende gabbros constitute a geochemically bimodal igneous rock association. Furthermore, the Early Triassic granites show the geochemical characteristics of shoshonitic rocks. All the rocks are characterized by enrichment in LILEs and LREEs, and depletion in HREEs and HFSEs, suggesting they formed in a subduction setting. Zircons from the Early Triassic gabbros have ε_Hf(t) values and T_DM2 ages of +7.6 to +10.7 and 735–1022 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of lithospheric mantle material that had been previously modified by subduction-related fluids. The Late Permian diorites have ε_Hf(t) values and T_DM2 ages of +0.5 to +9.5 and 853 to 1669 Ma, respectively, while they have high contents of Al₂O₃, Fe₂O₃, and low contents of SiO₂, Cr, and Ni, indicating Late Permian diorites should derive from the mantle and are influenced by some crustal material. Early Triassic granitic rocks have a wide range of ε_Hf(t) values and T_DM2 ages of −4.8 to +9.4 and 852 to 2136 Ma, respectively. Their zircons imply that the Early Triassic granites could be mainly derived from partial melting of the crust, with minor contribution of the crustal material of an ancient crust. The Early Triassic bimodal intrusive rocks in Yanbian area, combined with the regional geologic information; therefore, record a final post-subduction extensional environment due to the break-off of the previously subducted slab.

The source of iron material and the mineralization process of iron skarn deposits within the eastern North China Craton are ambiguous. In this study, we present new mineral chemical data of the Jinling skarn deposit, located in western Shandong Province, east China. Based on the petrography study and mineral chemical data, we suggest that the Jinling iron skarn deposit is hydrothermal and the metallogenic iron is enriched by leaching of Fe-rich fluids derived from primitive magmatic melt from the solidified diorites. The Jinling iron skarn deposit formed as a result of several mineralization processes: (1) Fe-rich hydrothermal fluids exsolved from a hydrous parental magma that was characterized by high iron content, oxygen fugacity (fO₂), and salinity; (2) the Fe content of the fluids was augmented during the alkali metasomatism stage via the leaching of Fe from the solidified dioritic rocks; (3) diopside and garnet in skarns formed under relatively alkaline and oxidizing conditions during the later prograde skarn stage; (4) during the retrograde skarn stage, amphibole, chlorite, epidote, phlogopite, serpentine, biotite, and chlorite formed under more oxidizing conditions, and subsequent mixing of the Fe-rich fluids with meteoric water triggered the precipitation of the massive magnetite; and (5) the final sulfide–carbonate stage was involved in the formation of carbonate and sulfide minerals as a result of a change in conditions from oxidizing to reducing.