Possible link between the oldest supracrustal unit and the oldest rock unit of China.

• 3.3–3.4 Ga may be the maximum deposition age of the Caozhuang Group. • Caozhuang zircons may derive from protracted reworking of a long-lived mafic source. • Anshan complex may contribute most of Caozhuang detrital zircons. Caozhuang Group (or Caozhuang supracrustal sequence) in Eastern Hebei, North China Craton (NCC) may represent the oldest supracrustal unit of China. Abundant Eoarchean and Paleoarchean detrital zircons (up to 3.88 Ga) in paragneisses of Caozhuang Group provide valuable memories of the earliest crustal evolution of China. There still remains confusion about the deposition time of the Caozhuang group, the origin and the igneous host rocks of their detrital zircons, and the earliest crustal evolution of NCC. In this study, the combined U–Pb and Lu–Hf datasets provide evidence that ~3.3–3.4 Ga is a probable estimate for the maximum deposition age of the Caozhuang Group. In addition, the increasingly subchondritic Hf isotopic compositions between 3.9 and 3.4 Ga reflected by the broadly linear Hf isotope evolution defined by Caozhuang detrital zircons may support the protracted intra-crustal reworking of a long-lived mafic source in composition with 176Lu/177Hf of 0.027. The Lu-Hf composition of the mafic source is similar to the average value of ocean floor basalts (176Lu/177Hf = 0.028) and Eoarchean-Paleoarchean Caozhuang mafic rocks (176Lu/177Hf = 0.026) in the same area. Based on the similarities between Caozhuang detrital zircons and TTG-hosted zircons of Anshan complex, as well as the significant differences with other Archean ancient complexes, the Anshan complex, where the oldest rock unit of China is preserved, may be the suitable host rocks for Caozhuang detrital zircons. [ABSTRACT FROM AUTHOR]