Provenance heterogeneity of uranium-bearing strata and its implications for uranium mineralization along the northern margin of Ordos Basin

The northern Ordos Basin hosts a world-class uranium metallogenic belt, yet the spatial variation of uranium-bearing strata—transitioning from the Lower Cretaceous strata in the west to the Middle Jurassic strata in the east—remains poorly explained. Previous studies have largely focused on individual stratigraphic units, leaving unresolved questions regarding how sediment provenance shifts across time and space, and how such shifts control the preferential localization of uranium mineralization.The newly discovered Saitai uranium deposit, located in this transition zone, provides a critical opportunity to address these gaps. Uranium mineralization in Saitai area occurs mainly in the upper submember of the lower member of the Middle Jurassic Zhiluo Formation (J 2 z 1−2 ), with secondary mineralization in Lower Cretaceous strata. To determine whether and how provenance variations control this spatial shift, this study conducted U-Pb dating and Lu-Hf isotopic analysis of detrital zircons from the Middle Jurassic-Lower Cretaceous strata in the Saitai deposit. The U-Pb dating results reveal three age clusters: 400–120 Ma, 2100–1500 Ma, and 2600–2200 Ma. Sedimentological analysis and comparative probability density plots reveal that the Middle Jurassic samples exhibited the strongest affinity with the Daqingshan and Wulashan areas,whereas Lower Cretaceous samples showed contributions from multiple provenance areas, including the Daqingshan, Wulashan, and Zhuozishan areas. Two zircon grains from The Huanhe-Huachi Formation exhibits ages of less than 121 Ma, suggesting that it was deposited during the middle-late Early Cretaceous. The Lu-Hf isotopic characteristics show significant variations in ε Hf (t) values, reflecting ancient crustal recycling. The destruction of the North China Craton (NCC) triggered the asthenospheric upwelling, mixing juvenile crustal materials with ancient crust preserved in strike-slip pull-apart basins such as Zhuozishan, jointly reflect the superimposed modification of the pre-existing crust by deep dynamic processes. Combied with the sedimentological features, we propose that the sediment provenance shifted from north to northwest between the depositional period of the Zhiluo Formation and the Early Cretaceous. During the Early Cretaceous, the paleocurrent directions were inconsistent with the migration pathways of ore-forming fluids, inhibiting uranium enrichment. This accounts for the phenomenon that ore-bearing strata literally transitioned from the lower submember to the upper submember of the lower member of the Zhiluo Formation and then to the Lower Cretaceous strata from east to west across the northern Ordos Basin. These findings provide critical constraints for reconstructing the Jurassic-Cretaceous prototype basins, paleogeomorphy, and for predicting uranium reservoirs.