Chemical Weathering of Detrital Sediments in the Taklamakan Desert, Northwestern China

Based on the analysis of major-element compositions of detrital sediments from the Taklamakan Desert of northwestern China, this paper aims to study chemical weathering in a hyper-arid desert environment. The major-element compositions are basically similar to the Upper Continental Crust but show a clear enrichment of CaO and depletion of Na2O and K2O, indicating the enrichment of carbonates and the decomposition of sodium and potassium silicates. The indexes of chemical alteration are relatively low and correlate negatively with the content of Na2O, implying that the degree of chemical weathering is weak and mainly controlled by the weathering of sodium feldspars. An A-CN-K model demonstrates that the detrital sediments from the Taklamakan Desert have a high homogeneity in the trend of chemical weathering. They are weathered less than sands and soil in many other Chinese deserts, and also less than similar detrital sediments in many other countries. This evidence suggests a low degree of mineralogical maturity in the Taklamakan Desert. The aeolian sediments of different ages have similar indexes of chemical weathering, suggesting that the degree of chemical weathering was consistent in the Taklamakan Desert throughout the period of aeolian deposition. The low degree of chemical weathering is caused principally by extreme aridity, rapid rejuvenation of detrital sediments associated with strong aeolian processes, and an intensive input of fluvial deposits, as well as a lack of vegetation. Due to the high concentration of erodible minerals, the desert is quite vulnerable to soil erosion and land degradation.