## 4 Results and Discussion
### Geochemical Zoning
In contrast, the Badain Jaran, Tengger, Hobq, and Mu Us deserts are surrounded by carbonate strata along the northern edge of the Qilian Mountains, the surrounding Alashan mountains, and the southern segment of the Helan Mountains, but these formations are not as extensive as those in the Kunlun Mountains [60]. Therefore, the CaO content in these deserts is lower compared to the Western Deserts. The Eastern Deserts, surrounded by areas lacking carbonate rocks [47], consequently have a lower CaO content. The second factor influencing the chemical composition of Chinese deserts is the supply of fresh material. This can be explored from multiple perspectives, including the erosion, weathering, transportation, and deposition of source materials. Chemical weathering leads to the dissolution of carbonate minerals and the gradual transformation of feldspars and ferromagnesian silicate minerals into secondary clay minerals. The weathering products are transported in the form of solutions or suspensions, resulting in the relative enrichment of weathering-resistant minerals like quartz in coarse fractions. Physical weathering, on the other hand, further fragments minerals like carbonates and ferromagnesian silicates, which are less resistant to physical weathering, leading to the relative enrichment of weathering-resistant minerals such as quartz in coarse fractions. From the perspective of material erosion supply and physical and chemical weathering, different deserts exhibit significant differences. In the Western Deserts, such as the Taklimakan Desert, surrounded by high mountains like the Tianshan, Pamirs, Kunlun, and Altun Mountains, with large river gradients, sparse vegetation cover, and extensive ice and snow cover on mountaintops (with more developed glaciers during the Quaternary glaciation), physical erosion is strong and chemical weathering is relatively weak. Overall, the Western Deserts are characterized by mobile sand dunes with strong physical weathering and weak chemical weathering. In contrast, the Eastern Deserts are predominantly covered by fixed sand areas, with weaker physical weathering but stronger chemical weathering [47], resulting in the partitioning observed in the constant element importance stacking diagram (Figure 6a). For the trace element importance stacking diagram (Figure 6c), it can be concluded that in desert regions such as Kumatag, Gurbantunggut, Taklimakan, and Qaidam, elements like S, Cl, and TC show significantly high importance. These elements are typically closely related to the chemical weathering processes in desert areas. Particularly under arid conditions, their accumulation may be influenced by variations in salinity and moisture. The noticeable geochemical differences in some elements are attributed to their differentiation, migration, and enrichment under varying climatic backgrounds and depositional environments. In the trace element clustering heatmap (Figure 7), the Western Deserts show a higher correlation with most trace elements. This likely reflects the geological background and depositional environment of the Western Deserts, where specific geological processes or rock compositions might lead to trace element enrichment. The Central Deserts follow in terms of correlation, while the Eastern Deserts exhibit lower trace element correlation, with only elements such as Rb and Corg. showing relatively better correlation. This may be related to the younger geological age and lower degree of chemical weathering in the Eastern Deserts. In the trace element factor weight distribution map (Figure 8), factors F1 and F2 have the highest weights in the Western Deserts, which may be related to the region's geological structure, rock composition, and chemical weathering processes. Other factors show weaker weights on the map. In the Central Deserts, besides F1 and F2, factors F3, F4, and F5 also have noticeable impacts, which may reflect the more complex geological background and chemical composition of the region.