Archean crustal evolution in the southeastern North China Craton: New data from the Huoqiu Complex

• Zircons from the Huoqiu Complex of the SE North China Craton yield Paleo- to Neo-Archean ages.
• Three age peaks at ∼3.02, ∼2.77 and ∼2.71 Ga record different crustal processes.
• Zircon U–Pb age of 3262 ± 35 Ma and REE data indicate possible existence of Paleoarchean crystalline basement.
• Sedimentary rocks of the Huoqiu Complex formed between 2.77 Ga and 2.71 Ga.

The southeastern margin of the North China Craton (NCC) is characterized by zircon ages of dominantly >2.6 Ga and differs significantly from most other regions in the NCC with mostly ∼2.5 Ga zircons. In order to better understand the Precambrian crustal evolution of the NCC, we conducted a study of in situ zircon U–Pb dating, trace element and Hf isotope analyses as well as whole-rock geochemistry on a comprehensive set of core samples from three drilling holes intersecting the basement rocks of the Huoqiu area at the southeastern margin of the NCC. Our data reveal three magmatic events at ∼3.02 Ga, ∼2.77 Ga and ∼2.71 Ga. In addition, seven analyses of possibly inherited zircon cores plot along a discordant line with an upper intercept age of 3262 ± 35 Ma, indicating possible existence of a Paleoarchean crystalline basement. The ∼3.02 Ga zircons have positive ɛHf(t) values close to the depleted mantle growth curve and their U–Pb ages are only slightly younger than the TDM1 model ages, hence recording a Mesoarchean crust-forming event. The ∼2.77 Ga zircons also register a period of crustal growth, but probably with some involvement of older crust. The ∼2.71 Ga zircons have lower ɛHf(t) values and older TDM1 model ages than the ∼2.77 Ga zircons, suggesting that the former were mainly derived from older continental crust, in contrast to the traditional idea that ∼2.7 Ga was a major period of crustal growth in the NCC.