Geochemical characteristics of surface aeolian sand in the Badain Jaran Desert, northwestern China: Implications for weathering, sedimentary processes and provenance

Abstract

Knowledge of the provenance of the aeolian sand in deserts is crucial for revealing their development and the corresponding driving mechanisms. As the second-largest desert in China, the Badain Jaran Desert (BJD) has developed the tallest megadunes on Earth. However, the material source of these dunes, especially the provenance of different particle size fractions, is debated. Here, we address these issues using new geochemical data, consisting of the major, trace, and rare earth elemental signatures of different particle-size fractions of dune sands in the BJD and sediments from potential source areas. The source area sediments are from the rivers originating in the Qilian Mts., the Gobi regions between the Heihe River and the BJD, the piedmont of the Gobi-Altay Mts., and the alluvial fan of the Beida Mts. The results show that the dune sands of the BJD are mainly derived from felsic source rocks subjected to weak chemical weathering in the source area. The fine fraction (<63 μm) of the aeolian sand in the BJD has experienced some degree of sedimentary sorting and recycling, despite its mineralogical immaturity. Furthermore, comparison of the immobile trace elements and rare earth element (REE) ratios of the samples from the BJD with those from the potential source regions, together with the results of multidimensional scaling and principal component analysis, shows that the coarse fraction (63–250 μm) of the dune sand in the BJD originated mainly from fluvial and Gobi deposits eroded from the Qilian Mts.; whereas the fine fraction has a mixture of provenances, including the Qilian Mts. and the Gobi-Altay Mts., although the latter contribution is of limited significance.