Zircon U-Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton

摘要

The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U-Pb and Lu-Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U-Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at-2.9 Ga,-2.7 Ga and-2.5 Ga. Metamorphic zircon U-Pb data obtained for these rocks show distinct metamorphic ages at-2.50 and-1.9-1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoicjiao-Liao-Ji Belt. Magmatic zircons have variable ε_(Hf)(t) values from —5.5 to +7.7 with model ages of 3.92-2.57 Ga, of which most ε_(Hf)(t) values are positive with a predominant peak of model ages at 3.4-3.1 Ga and a subordinate peak at 2.8-2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4-3.1 Ga and 2.8-2.7 Ga, and acrustal reworking event with minor juvenile additions at-2.5 Ga in the Jiaodong Terrane.