Provenance of aeolian sediment in the Taklamakan Desert of western China, inferred from REE and major-elemental data

摘要

To identify the provenance of aeolian deposits in the extensive dune field in the Taklamakan Desert is of great importance for understanding the formation of this, the largest sand sea in China. The opinions from earlier studies are quite dipolar and are as follows: (a) local origin of the dune sands in different parts of the desert on the basis of various heavy mineral assemblages; and (b) strong homogenization of the sands in the entire Taklamakan on the basis of geochemical data from whole-rock samples. By separately examining the REE characteristics and major-elemental composition in coarse and fine fractions of the samples from aeolian deposits, this paper provides new data for interpreting sources of aeolian deposits in the Taklamakan. The sampling sites are distributed in four different fluvial systems, i.e. the areas of the Keriya River, Niya River and Cele River in the southern part and the northern margin near the Tarim River (Fig. 1). Our results show that there are some significant differences in concentrations of trace elements and in REE features between the coarse and the fine fractions of the aeolian sediment. The major-elemental and REE data suggest that the coarser sand is different from area to area in the desert rather than a homogenization of the entire basin. The fine fractions (mainly silts) are more homogenized. The regional difference of coarse fractions in the study areas is consistent with the fluvial and wind systems in the basin. This confirms that the sands are often mixed between the northern and southern parts but there is much less mixing along the east-west direction. It should be emphasized that not only glacial and aeolian processes but also fluvial and lacustrine processes have jointly contributed to the formation of the huge sand sea. In addition, little variation is found between old and young sands in two sediment sequences in the central part of the desert, indicating consistency of sand sources in a given site during the last 40 ka.