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• The northern UBD and YD have similar trace metal compositions and source areas; • The BJD and southern Mongolian Gobi are the main direct sources of the UBD; • Nd isotopes indicate ∼ 25% input from the LM for sands in the northern UBD; • The northern UBD and YD act as an intersection for long-distance aeolian transport. Tracing the provenance of aeolian sand in deserts is essential for comprehending the mechanisms underlying desert formation and sediment transportation processes. There are multiple sand belts that interconnect major deserts within the Alxa Plateau of northern China, as evidenced by satellite images and field research. However, the aeolian sand transport from the Badain Jaran Desert (BJD) to the Yamalik Desert (YD) and Ulan Buh Desert (UBD) through these expanding sand belts is still being underestimated. In this study, we analyzed trace metal contents and Sr-Nd isotopic compositions in the < 125 μm fraction of dune sands in the northern UBD and YD, along with bedrocks from the Langshan Mountains (LM). Based on bivariate plots of Zr vs. Hf, Zr/Hf vs. Hf, Cr/V vs. Y/Ni, and Th/Co vs. Th/Sc, the aeolian sands in the northern UBD and YD have similar sources but are different from those in the southern UBD. Comparison of Sr-Nd isotopes with potential source areas suggests that fine-grained aeolian sands in the YD and northern UBD are mainly sourced from the BJD and the southern Mongolian Gobi. Although the heterogeneity of bedrock samples impeded the precise interpretation of contributions from all potential sources, the ε Nd (0) signatures in the UBD suggest that up to 25% of the fine-grained sand is derived from the LM, which displays highly negative ε Nd (0) values. On a larger geographical scale, the northern UBD serves as a transfer intersection for long-distance transportation of sand and dust ultimately sourced from the Central Asian Orogen and northern Tibetan Plateau. This study also demonstrates the essential role of sand belts in facilitating aeolian transport within the Alxa Deserts. [ABSTRACT FROM AUTHOR]