The Neoproterozoic continental extension tectonic event in the Chuncheon area of the northern Gyeonggi massif in the Korean Peninsula and its implication for the tectonic correlation between the Korean Peninsula and China

The Meso-Neoproterozoic Gubongsan group in the Chuncheon area of the northern Gyeonggi massif in the southern Korean Peninsula was studied to check its correlation with the Meso-Neoproterozoic rocks of the Sangwon system in the northern Korean Peninsula and those of the Qingbaikou system in the southeastern margin of the North China craton. The Gubongsan group consists of the Pyeongchonri, Siniri, and Gamjeongri formations and the upper limit of sedimentation ages of each formation are 1058 Ma, 978 Ma, and 845 Ma, respectively. The detrital zircons in the Pyeongchonri and Siniri formations have two age peaks of ∼1.6–1.5 Ga and 1.2–1.1 Ga. The detrital zircons in the Gamjeongri formation has an age peak of 0.9 Ga. The Gubongsan group was intruded by metabasite and meta-intermediate rock ca. 888–795 Ma. To the south of the Gubongsan group, metabasite intruded ca. 910 Ma. These igneous rocks are plotted in the within-plate basalt field and have enriched LREE without negative Nb, Ta, and Ti anomalies. They show εHf(t) values from −1.72 to 14.10 and are plotted between E-MORB and OIB within the MORB array, representing that they formed from the juvenile mantle. This study represents that the sedimentation in the Gubongsan group occurred during Neoproterozoic in the extensional rifting environment with igneous activities in the later stage of extension. The metabasite in the Gubongsan group shows similar Neoproterozoic emplacement age and extension-related geochemical characteristics to the Sariwon sill in the Sangwon system located in the southern Nangnim massif, and the Dalian and Chulan sills in the Qingbaikou system of the southeastern margin of the North China craton. Not only the correlation of metabasite but also the youngest age of the detrital zircons and age provenance in the sedimentary rocks of the Gubongsan group are similar to those of the Sangwon system and the Qingbaikou system. This study represents that the Meso-Neoproterozoic rocks in the Gubongsan group can be correlated with those in the Sangwon system and the Qingbaikou system. These correlations indicate that the northern Gyeonggi massif can be correlated with the southern Nangnim massif and the southeastern margin of the North China craton. © 2023 Elsevier B.V.