## 4 Results and Discussion
### Geochemical Zoning  
Based on the analysis of geochemical background values and baseline values, it was observed that the enrichment or depletion patterns of different elemental indicators in various deserts exhibit certain similarities (Figures 3 and 4). However, as shown in Figure 3, classifying or zoning different deserts based on enrichment or depletion alone is significantly influenced by human factors and tends to be rather coarse. Therefore, to improve the precision of geochemical zoning, it is beneficial to utilize machine learning techniques in conjunction with some geochemical indicators [55]. By applying these methods, the 12 desert areas can be divided into several geochemical zones. This approach enhances the visualization of zoning results, increases the efficiency of zoning analysis, and facilitates the evaluation and comparison of geochemical regional systems [56; 57; 58; 59]. From the three triangular diagrams (Figure 5), it is clear that the various desert areas are divided into three distinct zones: Eastern Deserts (1. Hunshandak, 2. Horqin, 3. Hulun Buir), Central Deserts (4. Badain Jaran, 5. Ulan Buhe, 6. Mu Us, 7. Hobq, 8. Tengger), and Western Deserts (9. Kumtag, 10. Gurbantunggut, 11. Taklimakan, 12. Qaidam). The SiO\({}_{2}\)/10-Al\({}_{2}\)O\({}_{3}\)-CaO triangular diagram (Figure 5a) reflects the relative proportions of quartz, carbonate, and silicate minerals. The Western Deserts, including Kumtag, Taklimakan, and Qaidam, are characterized by significantly higher carbonate mineral ratios, relatively lower quartz ratios, and intermediate silicate mineral content. The (K\({}_{2}\)O + Na\({}_{2}\)O)-CaO-TFe\({}_{2}\)O\({}_{3}\) triangular diagram (Figure 5b) shows the relative proportions of feldspar, carbonate, and ferromagnesian silicate minerals in the samples. In the Western Deserts, Kumtag, Taklimakan, and Qaidam exhibit high carbonate mineral ratios and low ferromagnesian silicate mineral ratios. The Central Deserts, such as Badain Jaran, Ulan Buhe, Mu Us, Hobq, and Tengger, as well as Gurbantunggut in the Western Deserts, feature intermediate carbonate mineral ratios. In contrast, the Eastern Deserts, including Hunshandak, Horqin, and Hulun Buir, show high feldspar mineral ratios and low carbonate mineral ratios. The CaO-K\({}_{2}\)O-Na\({}_{2}\)O triangular diagram (Figure 5c) reflects the relative proportions in the content of carbonate, potassium feldspar/muscovite, and plagioclase in the samples. The Western Deserts (Kumtag, Taklimakan, and Qaidam) exhibit high carbonate mineral ratios, low potassium feldspar/muscovite, and low plagioclase content. The Central Deserts (Badain Jaran, Ulan Buhe, Mu Us, Hobq, and Tengger) and Gurbantunggut in the Western Deserts have intermediate carbonate mineral ratios, moderate plagioclase content, and high potassium feldspar/muscovite ratios. Conversely, the Eastern Deserts, including Hunshandak, Horqin, and Hulun Buir, are characterized by high plagioclase mineral ratios and low carbonate mineral ratios. In the constant element feature importance stacked plot (Figure 6a), CaO, MgO, and TFe\({}_{2}\)O\({}_{3}\) are significantly more important in the Kumtag, Gurbantunggut, Taklimakan, and Qaidam deserts compared to other deserts. The importance is somewhat lower in the Badain Jaran, Ulan Buhe, Mu Us, Hobq, and Tengger deserts, with Hunshandak, Horqin, and Hulun Buir deserts showing the lowest levels of importance. The primary factor influencing the variation in constant elements is the composition of the source rocks. From the geochemical map of calcium oxide in China, it is evident that the Kunlun Mountains and the North Tian Shan Mountains are rich in marine carbonate rocks. These carbonate minerals are continuously supplied to the Taklimakan, Qaidam, and Kumtag deserts through river systems. The Tianshan Mountains and the Altai Mountains near Gurbantunggut also have significant carbonate rock formations, providing a certain amount of carbonate minerals to the Gurbantunggut Desert.