Abstract:

The U-hosting strata of sandstone-type uranium deposits in the Kelulun sag are the Lower Cretaceous Damoguaihe and Yimin Formations. However, systematic studies on their sediment provenance remain limited. This study integrates petrology, zircon U-Pb dating and sandstone geochemistry to constrain the sediment sources of the U-hosting strata and to support further uranium exploration in this area. Petrological observation shows that the gravel and debris components of Yimin and Damoguaihe Formations in the western part of Kelulun sag are mainly granitic, with minor volcanic contributions. Proximity to the Tarbagete uplift corresponds to increased gravel content, coarser grain size, and poorer sorting and rounding of granitic clasts. Some fine conglomerates consist of quartz, feldspar and other minerals derived directly from weathered granite, showing near-source rapid accumulation. In contrast, drilling cores from the eastern sag show gravel assemblages dominated by volcanic rock fragments, with granite gravel being rare. Zircon U-Pb dating results show that detrital zircon ages in the eastern part are mainly concentrated in three age groups of 170-154 Ma, 180-177 Ma and 269-244 Ma. These age peaks correlate well with Early-Middle Jurassic granites and Middle-Late Jurassic volcanic rocks surrounding the sag. Detrital zircon ages in the western part of the sag is mainly concentrated in 257-236 Ma, closely matching the ages of widespread Permian and Triassic magmatic rocks in the Tarbagete uplift, indicating that detrital sediments in the west were mainly derived from this uplift area. Major and trace element geochemistry of sandstones shows low compositional maturity, consistent with rapid accumulation, and points to felsic source rocks. The comprehensive analysis shows that uranium-bearing Permian and Triassic granites in the northwestern provenance area are the main sediment source and a key uranium source for the U-hosting strata and associated mineralization in the western Kelulun sag. In contrast, sediments in the eastern sag were mainly derived from Jurassic volcanic rocks and granites in  Hanwula uplift along the eastern margin.

Key words: sandstone-type uranium, U-hosting strata, zircon age determination, geochemistry, sediment source analysis, Kelulun sag, Hailaer basin