Early Neoarchean (∼2.7 Ga) tectono-thermal events in the North China Craton: A synthesis

Abstract

The North China Craton (NCC) is characterized by major ∼2.5 Ga tectono-thermal events and is thus different from many other cratons worldwide where ∼2.7 Ga events are well developed. However, whole-rock Nd and Hf-in-zircon isotopic compositions of ∼2.5 Ga crustally derived granitoids reveal that they mainly formed through reworking of late Mesoarchean to early Neoarchean continental material. We review the spatial distribution, rock types, geochemical and Nd–Hf isotopic compositions of ∼2.7 Ga granitiods that are widely identified in the NCC, including eastern Shandong, western Shandong, Huoqiu, Hengshan, Fuping, Zanhuang, Zhongtiao and Wuchuan. These granitoids are mainly tonalitic in composition and frequently underwent strong metamorphism, deformation and anatexis. They show large variations in SiO2, total FeO, MgO and CaO, and can be subdivided into two types in terms of their REE patterns. More importantly, whole-rock Nd and Hf-in-zircon isotopic compositions indicate that the strong ∼2.7 Ga tectono-thermal event mainly involved juvenile additions to the continental crust. The early Neoarchean was the most important period for rapid production of new continental crust in the NCC. The main difference of the NCC from many other cratons worldwide is a strong and widespread superimposed tectono-thermal event at ∼2.5 Ga that stabilized the cratonic assemblage.