| Abstract:The Changcheng System in the Ordos Basin is currently a key target horizon for deep hydrocarbon exploration. However, research on its depositional age, filling framework, and provenance composition remains relatively limited. Based on the latest drilling data and core samples, this study has conducted petrographic analysis, detrital zircon dating, and stratigraphic correlation of the Changcheng System. Regional correlation reveals that the Changcheng System in the Ordos Basin exhibits a distinct "bipartite" lithological character, that is the lower section consists of mafic volcanic rocks while the upper section comprises clastic sedimentary rocks. This filling framework is highly similar to that of the Xiong'er Rift System. Combined with previous data, our new geochronological results constrain the basal age of the upper sedimentary section to 1673~1632 Ma, which aligns with the revised maximum depositional age of the Changcheng System in the Yanliao area. This age interval corresponds to a significant anorogenic magmatic event in the North China Craton, recording prolonged extension following a large igneous province event. The remaining zircons define three primary age peaks at ~1.82 Ga, 2.05 Ga, and 2.5 Ga. These were likely sourced from coeval granitic intrusions in the Yinshan and Taihang Mountains, as well as recycled Paleoproterozoic metasedimentary rocks. A minor contribution may derive from proximal granitoids within the basin. |
