Geodynamic evolution of lithospheric removal of the North China Craton: Constraints from late Mesozoic volcanic rocks in the Bohai Bay Basin, East China

The subduction history of Paleo-Pacific Plate (PPP) related to lithospheric removal in the North China Craton (NCC) still poorly constrained. To address this issue, we report a detailed investigation of LA-ICP-MS zircon U-Pb chronology, geochemistry, and Sr-Nd isotope compositions of a set of late Mesozoic volcanic rocks collected from boreholes in the Bohai Bay Basin. Late Jurassic (150.6 Ma) adakitic rocks are trachyandesites with high MgO (1.41-5.78 wt%), Mg# (46-64), Cr (25.1-110 ppm) and Ni (12.4-34.0 ppm) contents similar to those of high-Mg adakitic rocks. These samples were probably the result of partial melting of a delaminated region of thickened lower continental crust. Early Cretaceous samples are basalt and trachyandesite. Trachyandesites (ca. 115 Ma) exhibit low epsilon Nd(t) values (-15.9 to-12.9) and older TDM2 ages (2.19-1.96 Ga), indicating that they originated in the ancient lower crust. Hornblende may have been the main residual phase in the source, suggesting that these samples were likely formed by partial melting of the lower crust at depths of 30-40 km. The coeval basalts are OIB-like series with depleted Sr-Nd isotopes, depleted Pb and no depleted Nb, implying that they were derived from a depleted mantle source metasomatized by recycled oceanic crust. Combined with those of previous studies, our findings show that subducted PPP beneath the NCC experienced local slab rollback and fast slab rollback during late Mesozoic, resulting in lithospheric removal and destruction of the NCC. Finally, the magmatic activity that marked the large-scale lithosphere removal ended after ca. 115 Ma.

Automated summary

Through the study of late Mesozoic volcanic rocks in the Bohai Bay Basin, it was found that there may have been delamination and partial melting of the thickened lower continental crust during the Late Jurassic. The samples from the Early Cretaceous period were likely partial melting products of the lower crust. The results suggest that the Paleo-Pacific Plate subducted beneath the North China Craton and experienced slab rollback, leading to lithospheric removal and destruction of the North China Craton.