Late Mesozoic magmatism in the Jiaodong Peninsula, East China: Implications for crust–mantle interactions and lithospheric thinning of the eastern North China Craton.

A section from the Linglong gold deposit on the northwestern Jiaodong Peninsula, East China, containing Late Mesozoic magmatic rocks from mafic and intermediate dikes and felsic intrusions, was chosen to investigate the lithospheric evolution of the eastern North China Craton (NCC). Zircon U–Pb data showed that low-Mg adakitic monzogranites and granodiorite intrusions were emplaced during the Late Jurassic (~145 ​Ma) and late Early Cretaceous (112–107 ​Ma), respectively; high-Mg adakitic diorite and mafic dikes were also emplaced during the Early Cretaceous at ~139 ​Ma and ~118 ​Ma, and 125–145 ​Ma and 115–120 ​Ma, respectively. The geochemical data, including whole-rock major and trace element compositions and Sr–Nd–Pb isotopes, imply that the mafic dikes originated from the partial melting of a lithospheric mantle metasomatised through hydrous fluids from a subducted oceanic slab. Low-Mg adakitic monzogranites and granodiorite intrusions originated from the partial melting of the thickened lower crust of the NCC, while high-Mg adakitic diorite dikes originated from the mixing of mafic and felsic melts. Late Mesozoic magmatism showed that lithosphere-derived melts showed a similar source depth and that crust-derived felsic melts originated from the continuously thickened lower crust of the Jiaodong Peninsula from the Late Jurassic to Early Cretaceous. We infer that the lower crust of the eastern NCC was thickened through compression and subduction of the Palaeo-Pacific plate beneath the NCC during the Middle Jurassic. Slab rollback of the plate from ~160 ​Ma resulted in lithospheric thinning and accompanied Late Mesozoic magmatism. Image 1 • Late Mesozoic low-Mg and high-Mg adakitic rocks are found in the northwestern Jiaodong Peninsula. • NCC lower crust thickened via compression and Middle-Jurassic subduction of Palaeo–Pacific plate. • The low crust of NCC is invariable and its lithospheric thinning occurred at the lithospheric mantle depth. • Slab rollback at ~160 ​Ma caused lithospheric thinning and Late Mesozoic magmatism. [ABSTRACT FROM AUTHOR]