Abstract: In this study, the ~2.5 Ga late Neoarchaean monzogranites have been identified for the first time in the Shaolanghe area of the northern margin of the North China Craton (NCC). Analyses of in situ zircon UPb ages, Hf isotopic data and wholerock major and trace element contents have been performed on the monzogranites. UPb dating of magmatic zircons indicates that the monzogranites formed in 2527±25 Ma, in the late Neoarchaean. Their massive structures contain partly gneissiclike and mediumcoarse grain structures with sporadic dark inclusions. The rocks have high Na and K, low P, a A/CNK ratio of 0.800.96, and belong to the highK calcalkaline series. The monzogranites exhibit enriched light rare earth elements (LREEs) with no δEu anomalies, and are enriched in large ion lithophile elements (LILEs) (e.g., Rb, Sr and Ba), and depleted in high field strength elements (HFSEs) (e.g., Nb, Ta, P and Ti). The zircon εHf(t) value and twostage Hfdepleted mantle model age (TDM2) range from 4.0 to 4.8 and 2712 to 3221 Ma, respectively, suggesting that the monzogranites were derived from fractional crystallization after melting of the juvenile Mesoarchaean and Neoarchaean lower crust. Relating to the newly discovered greenstone belt and TTG igneous rocks of the Archean in the Shaolanghe area in recent years, this paper proposes that there exists a Precambrian basement in the Shaolanghe area, possibility in the form of an ancient microblock. The formation of the monzogranites is an important symbol of cratonization at the end of the Neoarchaean in the NCC. Although the geochemical characteristics of the monzogranites indicate their probable association with subduction, we consider such subduction or collision between arc and continent or two continents limited and at a smallscale in the late Neoarchaean, quite different from the tectonic plate system.

Key words: monzogranite, late Neoarchaean, Precambrian basement, Shaolanghe area, northern margin of the North China Craton