Following the final cratonization of the North China Craton (NCC) through the assembly of major crustal blocks, the craton witnessed post-collisional magmatism during late Paleoproterozoic with the formation of diverse types of magmatic suites in the western and eastern margins of the Trans-North China Orogen (TNCO). Here, we investigate the anorogenic granitoid and associated gabbro from the Miyun complex located at the eastern margin of the TNCO. We present petrology, geochemistry, and zircon U-Pb, and Lu-Hf data on these rocks. The granite pluton is composed of a rapakivi phase with almost totally digested mafic magmatic enclaves, whereas the granite phase hosts gabbroic enclaves. The granitoids show high SiO2 content (71.28 to 78.83 wt%), with peraluminous A2 type affinity and within plate (rift-related) features. The magmatic zircon grains from the granite yielded 207Pb/206Pb weighted mean age of 1696 Ma. A similar crystallization age of 1683 Ma for the gabbro indicates coeval bimodal magmatism. Both rocks carry zircon xenocrysts with older ages that are consistent with the magmatic and metamorphic events recorded from the basement rocks. The εHf(t) values of the zircon grains from the granitoid are markedly negative (−7.9 to −5.0) with two-stage Hf crustal model ages (TC DM) ranging from 2688 Ma to 2855 Ma, indicating the involvement of Mesoarchean to Neoarchean crustal components in the magma source. In contrast, the zircon grains from gabbro show both positive and negative εHf(t) values, suggesting magma derivation from depleted mantle sources with minor juvenile crustal component. We envisage that lower crustal melting induced by mantle-derived mafic magmas during post-collisional rifting generated felsic magmas, into which the mafic magma was injected, resulting in magma mixing and mingling. In conjunction with the information from post-collisional magmatic suites in the adjacent locations including gabbro-anorthosite complex, and similar aged magmatic complexes within the TNCO, we propose a major post-collisional magmatic event in the NCC which involved extensive mantle upwelling and lower crustal melting.
Bibliographical noteFunding Information:
We thank Professor Guochun Zhao, Editor-in-Chief, and two anonymous referees for kindly evaluating our paper and providing us with constructive comments which improved this work. This study was funded by the Fundamental Research Fund of Central Universities (Grant 2652018048) to Cheng-Xue Yang and Foreign Expert Grants to M. Santosh from the China University of Geosciences Beijing. We appreciate our team members Bing Yu, Haidong Liu, and Yuesheng Han for accompanying us during fieldwork for discussions. This research was partially supported by NRF 2017R1A6A1A07015374, 2019R1A2C1002211and by KBSI under the R&D program (Project No. C030440) supervised by the Ministry of Science and ICT, Korea to Sanghoon Kwon. This study also received partial support from Basic Research Project (GP2020-003; Geological survey in the Korean Peninsula and publication of the geological maps) of Korea Institute of Geoscience and Mineral Resources (KIGAM) to Sung Won Kim, funded by the Ministry of Science, ICT (Information, Communication and Technology), and Future Planning, Korea.
© 2020 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology