ABSTRACT

Zircon U-Pb isotopic data on the early Cretaceous Dalongshan granitoids in the Yangtze Foldbelt of Southeast China provides evidence for the incorporation of old Archean crustal material. The age of inherited radiogenic lead is determined by the three-dimensional U-Pb discordia plane method to be about 3330±180 Ma, indicating that the early Archean basement probably exists underneath the northwest part of the Yangtze Foldbelt. The nature of the source region of initial lead in the zircon demands that the Archean basement is responsible for a lower crust or a depleted mantle.