Characterizing episodic orogenesis and magmatism in eastern China based on detrital zircon from the Jiaolai Basin

Abstract

The eastern China region is composed of the North China Craton (NCC) and the Yangtze Craton (YC), both of which underwent episodic orogenesis and magmatism. The Jiaolai extensional basin occurs at the southeastern boundary between the NCC and YC. Here we employ combined age and trace element data on detrital zircon grains in the Cretaceous Laiyang Group of the Jiaolai Basin to gain insights on magmatism and average melt compositions of the Archean to Cretaceous source rocks. Detrital zircon data suggest that the eastern China region was characterized by five main stages of crustal evolution and magmatism. The ∼2500 Ma detrital zircon population with positive ε_Hf(t) values trace new crustal growth during the Archean. Most Paleoproterozoic zircon grains are characterized by negative ε_Hf(t) values indicating reworking of the ancient crust. Additionally, the Y/Gd ratios indicate a thickened crust, and the low Ce/Ce* and Eu/Eu* values suggest low oxygen fugacity conditions of magmatism during this period. The Neoproterozoic zircon population displays low U/Yb ratios suggesting less input of slab fluid during juvenile crust generation along the western and northern margins of the YC. The Triassic zircon have high U/Yb and low Th/U ratios denoting extensive involvement of slab fluid and crustal metamorphism during the collision between the NCC and YC. The Th/Nb and Hf/Th ratios of Cretaceous detrital zircon grains are similar to those from arc-related/orogenic setting, and their Hf isotopes are consistent with melting of a composite crust with YC crust wedged into the NCC crust.