Geochemistry of aeolian sand in the Taklamakan Desert and Horqin Sandy Land, northern China: Implications for weathering, recycling, and provenance

Abstract

Geochemical studies examining surface aeolian sediments are significant for understanding Earth’s surface processes and determining sediment provenance in arid and semi-arid regions. However, there is limited research on the geochemical comparison of aeolian sediments formed under distinctive tectonic and climatic settings. Surficial sand samples from the Taklamakan Desert and Horqin Sandy Land in northern China were collected, and the major, trace, and rare earth elements (REEs) in the bulk samples, fine fractions (<75 µm) and coarse fractions (>75 µm) of sand were analyzed. This study aimed to explore the spatial variation in the geochemical composition of aeolian sand and its drivers. The results show that differences between the two regions are primarily caused by the intensity of chemical weathering, sedimentary recycling, and provenance. The mean chemical proxy of alteration (72.3 vs. 77.8) and the Parker's weathering values (37.8 vs. 55.8) both suggest the bulk samples from the Horqin Sandy Land experienced more intense chemical weathering, whereas physical weathering is a dominant process in the Taklamakan Desert. These differences may be attributed to the different climatic conditions in the two regions and the exposure time to weathering. A combination of the index of compositional variability and immobile trace element ratios shows that aeolian sand in the Horqin Sandy Land underwent more intense sedimentary recycling than sediments in the Taklamakan Desert. REEs ratios (such as Cr/V and Y/Ni) and the Al2O3-CaO*+Na2O-K2O (A-CN-K) diagram indicate aeolian sand in the Taklamakan Desert is probably derived from mixed source rocks of tonalite, granite, and granodiorite. Eu anomaly vs. (La/Yb)N diagrams suggest that the primary source-rocks contributing to the coarse and fine fractions in the Horqin Sandy Land are different but mainly derived from the Great Hinggan Mountains. Differences in the provenance of the fine- and coarse-grained fractions are primarily controlled by interactions between wind and fluvial systems. This study confirms that surface processes and sediment provenance in drylands of northern china have distinct spatial differences, implying that geochemical signatures in aeolian sand need to be interpreted in the specific climatic and tectonic contexts.