Geochemical characterization of major elements in Gurbantunggut Desert sediments, northwestern China and their regional variations

Abstract

• Mineralogical maturity increased from the piedmont to the desert center. • Provenance controls the regional differences in major element compositions. • Transport, sorting, recycling, and chemical weathering affect the sand compositions. • River sands constitute a significant source of sands in this desert. • Extensive vegetation coverage contributes to the regional differences in this desert. Identifying the geochemical composition of desert sands in the Gurbantunggut Desert is essential for understanding the formation of desert dunes in the mid-latitudes. In this study, we collected samples of desert sands (125–250 μm), fluvial sands, and lacustrine sands across the Gurbantunggut Desert and calculated the sand drift potential at four meteorological stations. The sand samples from the Gurbantunggut Desert were mostly enriched in SiO 2 , while the other major elements were depleted compared to those of the Upper Continental Crust (UCC). The chemical weathering indices (α Al E, CIA, and WIP) indicate that the sand-sized sediments in the Gurbantunggut Desert are in the initial stage of continental chemical weathering. SiO 2 and K 2 O contents as well as mineralogical maturity of the desert sands increased from the piedmont to the desert center. UCC-normalized distribution patterns were also consistent along this transect due to the homogenization of desert sand composition, whereas the concentrations of other major elements (except for TiO 2 and MnO) decreased. We conclude that (1) regional variations in the composition of the Gurbantunggut Desert sands primarily reflect differences in provenance, transport, sorting, recycling of the sediments, and vegetation cover as well as the chemical weathering; and (2) differences in indices describing the major element composition of the sands reflect regional variations in provenance from the mountains to the depositional basin. Sands within piedmont rivers possess major element characteristics similar to those of dune sands in the region, suggesting that rivers represent a significant source of sands in the desert.