Meso-Neoproterozoic tectono-thermal evolution in the northern margin of North China Craton: Constraints from zircon (U-Th)/He ages

Due to the complicated tectonic and sedimentary history and the lack of effective paleo-thermal indicators, the Meso-Neoproterozoic thermal history of the Yanliao rift zone in the northern margin of the North China Craton is ambiguous, which causes the maturation evolution of ancient source rocks controversial. In this study, zircon (U-Th)/He dating is used to study the tectono-thermal evolution of the Yanliao rift zone since the Mesoproterozoic, and we also analyzed the maturation evolution stages of two sets of Mesoproterozoic source rocks. The single-grain zircon (U-Th)/He ages from the Meso-Neoproterozoic strata in the Yanliao rift zone are all younger than the corresponding stratigraphic ages and therefore recorded the thermal information in the past. Moreover, the single-grain zircon (U-Th)/He ages of the Neoproterozoic Longshan formation show a negative correlation with the effective uranium concentration. The forward and inverse coupling simulation revealed that the Yanliao rift zone experienced two rapid cooling events of 440~320 Ma and 220~0 Ma, probably related to the collision between the Bainaimiao island arc and the northern margin of the North China Craton and the subduction of Mongolia Okhotsk oceanic crust below the eastern North China Craton, respectively. In addition, the formation temperature variations at the end of Ordovician and the end of Triassic had an important influence on the maturation evolution of Mesoproterozoic source rock.