Using detrital zircon systematics to trace the sediment sources of Jurassic uranium-bearing sandstones in the western Ordos Basin, China: implications for uranium exploration in a sedimentary basin

Abstract

ABSTRACT The Jurassic Zhiluo Formation in the western Ordos Basin is known for hosting economically significant sandstone-type uranium deposits. However, the understanding of sediment sources for this formation, crucial for guiding uranium exploration, has been a subject of controversy. This study aims to address this issue by presenting a systematic dataset derived from detrital zircons found in the uranium-bearing sandstones of the Zhiluo Formation. The dataset includes U‒Pb dating, trace element analyses, and in-situ Hf isotope compositions. The detrital zircons analysed are predominantly of magmatic origin, as indicated by a Th/U ratio greater than 0.4. Their U‒Pb ages can be broadly categorized into a predominant population ranging from 170 to 500 Ma, with a peak ca. 300 Ma. Additionally, there are two minor age populations: 1600–2050 Ma (peaking at ca. 1850 Ma) and 2300–2650 Ma (peaking at ca. 2500 Ma). The εHf(t) values of these zircons exhibit a range from −27 to 7, concentrating mostly from −16 to 5. Importantly, none of them aligns above the deficit mantle evolutionary line in an εHf(t) vs. age covariant diagram. A comprehensive comparison of the analytical U‒Pb ages and Hf isotopic results with previously reported data from adjacent geological units surrounding the western Ordos Basin suggests that the primary provenance supply area for the sandstones is the Alxa Block, particularly the uranium-rich felsic rocks within it. Minor contributions are inferred from the Yinshan Block and the Qilian Orogenic Belt. The northwestern region of the study appears to be the primary prospect area for uranium exploration, and we have proposed effective measures to refine the exploration target area and enhance exploration efficiency. Overall, the study provided crucial insights into deducing provenance supply areas and transport paths, with implications for uranium exploration in sedimentary basins worldwide.