Provenance analysis signposts for sedimentary uranium exploration in aeolian sandstone systems: Insights from the Luohe Formation, Western Ordos Basin

Abstract

The Lower Cretaceous Luohe Formation in the western Ordos Basin, North China, represents a rare aeolian sedimentary system with distinctive “uranium-bearing” characteristics. Sedimentary source of the uranium-bearing sandstones in this formation, which is crucial for advancing uranium exploration efforts, remains ambiguous. This study undertakes a comprehensive investigation encompassing petrology, geochemistry, and detrital zircon systematics (including zircon U–Pb ages, trace elements, and Hf isotopes) on the aeolian sandstones of the Luohe Formation within the western Ordos Basin. The objective is to provide crucial insights into conventional exploration for sedimentary uranium resources within aeolian sedimentary systems in intracontinental basins. Detrital zircon ages are categorized into a predominant age grouping within the Phanerozoic era (210–450 Ma), with notable peaks observed at 260 Ma and 420 Ma. Additionally, two minor age clusters are identified in the Early Paleoproterozoic (2240–2600 Ma), notably peaking at 2460 Ma, and the Late Paleoproterozoic (1600–2150 Ma), with a peak observed at 1850 Ma. Integrating the geochemical discrimination diagrams, it is suggested that the Alxa Block to the west of the Ordos Basin serves as the main provenance supplier of the hard detrital zircons. The uranium-bearing debris from the Alxa Block underwent sedimentary recycling and, therefore, were transported to the paleouplifts that formed on the western Ordos Basin during the Late Jurassic to Early Cretaceous. The paleoclimatic conditions characterized by prolonged arid periods interspersed with brief humid and warm episodes are crucial for the unique “uranium-bearing” nature of the sandstones. The sedimentary environment, dominated by aeolian deposition with localized fluvial deposition at basin-mountain interfaces, is identified as an ideal setting for uranium storage within aeolian sedimentary systems. We finally propose a generalized approach for exploring uranium reservoirs in aeolian sandstone systems at the basin level.