Mesoproterozoic magmatic events in the eastern North China Craton and their tectonic implications: Geochronological evidence from detrital zircons in the Shandong Peninsula and North Korea

摘要

Whether any Grenvillian magmatic records are preserved in the North China Craton(NCC) is a key issue to understand the Proterozoic tectonic evolution of the NCC and its correlation to the supercontinent Rodinia. Meso- to Neo-proterozoic sedimentary series is well exposed in the NCC, but magmatic events in this period, especially of 1.3-1.0. Ga, have seldom been reported. New U-Pb isotopic dating and Hf isotopic composition analyses have been carried out in this study using SIMS and LA-ICP-MS methods on detrital zircons from sandstones of the Tumen Group in the Shandong Peninsula and quartz sandstones of the Sangwon System in the Phyongnam Basin, North Korea. The age populations of the detrital zircons of the Tumen Group are at ~. 2.5. Ga, ~. 1.85. Ga, ~. 1.7. Ga, ~. 1.58. Ga, ~. 1.5. Ga, ~. 1.36. Ga and ~. 1.2. Ga and those of the Sangwon System are at 1.88-1.86. Ga, ~. 1.78. Ga, 1.62-1.58. Ga, 1.46-1.41. Ga, ~. 1.32. Ga, ~. 1.17. Ga and ~. 980. Ma. Most of the age peaks of Neoarchean and Proterozoic correspond to the significant tectonic-magmatic-thermal events previously recognized in the NCC, revealing that the main provenances of the Tumen Group and the Sangwon System are Early Precambrian basement and Late Paleo- to Meso-proterozoic magmatic rocks of the NCC. Furthermore, the youngest detrital zircon ages of ~. 1.1. Ga from the Tumen Group and 984. Ma from the Sangwon System, as well as 910. Ma Rb-Sr whole rock isochron age of a limestone from the Tumen Group and 899. Ma mafic sills intruding the Sangwon System suggest that both groups were deposited in the Neoproterozoic, coevally with the Qingbaikou System in the Yanliao Aulacogen. The common zircon ages of 1.3-1.0. Ga from the Tumen Group and the Sangwon System, as well as the contemporaneous Penglai and Yushulazi Group in the eastern margin of the NCC, indicate that during the deposition of these sediments there have been significant contributions from Grenvillian magmatic rocks in the eastern NCC. This may provide clues to understand the possible relationship of the NCC and the supercontinent Rodinia. Moreover, the positive εHf(t) and ~. 2.8. Ga crust model ages of detrital magmatic zircons of 2.8-2.4. Ga suggest that there have been significant crustal growth at ~. 2.8. Ga in the eastern margin of the NCC, same as in other areas of the NCC.