# Provenance and Paleo-Environment of the Late Carboniferous Bauxite Formations in Southern Shanxi
## 4 Result
### 4.3. Geochemical Characteristics of Elements  
#### 4.3.1 Major Elements  
Based on the test results for the major elements (Table 1), the bauxite (Y8) in the Jinyu profile primarily comprises Al\({}_{2}\)O\({}_{3}\) with a mass fraction of 60.80 wt.%, followed by SiO\({}_{2}\) (20.00 wt.%), TiO\({}_{2}\) (2.60 wt.%), TFe\({}_{2}\)O\({}_{3}\) (2.21 wt.%), and minor amounts of MgO, K\({}_{2}\)O, and CaO, resulting in a chemical index of alteration (CIA) of 99.09. The clay rocks above the bauxite (Y5, Y6, Y7, and Y9) are chiefly composed of SiO\({}_{2}\) (38.63 wt.%) and Al\({}_{2}\)O\({}_{3}\) (33.93 wt.%), with secondary amounts of TFe\({}_{2}\)O\({}_{3}\) (1.89 wt.%) and minor amounts of TiO\({}_{2}\), CaO, MgO, K\({}_{2}\)O, and a CIA ranging from 92.98 to 99.39. The iron-rich clay rocks below the bauxite (Y10, Y11) mainly contain SiO\({}_{2}\) (43.55 wt.%), followed by Al\({}_{2}\)O\({}_{3}\) (31.80 wt.%), TFe\({}_{2}\)O\({}_{3}\) (7.53 wt.%), TiO\({}_{2}\) (1.52 wt.%), and minor amounts of K\({}_{2}\)O, MgO, and CaO, with a CIA ranging from 89.48 to 96.37. The relatively low CIA value of Y11 is attributed to its high K\({}_{2}\)O content (3.68 wt.%), which is likely associated with mica (Figure 6). In the Jinshi profile, bauxite (S8) is predominantly composed of Al\({}_{2}\)O\({}_{3}\) with a mass fraction of 61.10 wt.%, followed by SiO\({}_{2}\) (21.30 wt.%), TFe\({}_{2}\)O\({}_{3}\) (1.89 wt.%), TiO\({}_{2}\) (1.25 wt.%), and small quantities of MgO, K\({}_{2}\)O, and CaO, resulting in a CIA of 99.80. The clay rock (S5) is chiefly composed of SiO\({}_{2}\) (43.30 wt.%) and Al\({}_{2}\)O\({}_{3}\) (31.70 wt.%), with secondary amounts of TFe\({}_{2}\)O\({}_{3}\) (4.13 wt.%), K\({}_{2}\)O (2.92 wt.%), and TiO\({}_{2}\) (2.06 wt.%), and minor amounts of MgO and CaO, and a CIA of 91.02. The aluminous rocks (S7 and S9) are primarily made up of Al\({}_{2}\)O\({}_{3}\) (47.50 wt.%), followed by SiO\({}_{2}\) (34.95 wt.%), TiO\({}_{2}\) (1.66 wt.%), TFe\({}_{2}\)O\({}_{3}\) (1.29 wt.%), and minor amounts of MgO, CaO, and K\({}_{2}\)O, with a CIA range of 98.04-99.61. Based on the test results for the major elements (Table 1), in the Jinyu profile, the content of SiO\({}_{2}\) is the highest in the uppermost sandstone (Y1) and the lowest in the bauxite layer (Y8). The content of Al\({}_{2}\)O\({}_{3}\) is the opposite of SiO\({}_{2}\). In addition, the TiO\({}_{2}\) and CAI content of the bauxite layer are also the highest. The content of TFe\({}_{3}\)O\({}_{2}\) is the highest in iron-bearing clay rocks. The content of CaO, MgO, K\({}_{2}\)O, and Al\({}_{2}\)O\({}_{3}\)/TiO\({}_{2}\) is higher in clay rocks. The content of other major elements was low, mostly less than 0.20 wt.%. In the Jinshi profile, the content of SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), TFe\({}_{3}\)O\({}_{2}\), and TiO\({}_{2}\) in the coal seam (S2) is the lowest. But the content of CaO and K\({}_{2}\)O in the coal seam (S2) is the highest. The content of SiO\({}_{2}\) is the highest in the sandstone (S3). Al\({}_{2}\)O\({}_{3}\) content is highest in bauxite. In addition, the CAI and TiO\({}_{2}\) content of the aluminiferous rock series is higher, 89.04 to 99.81. The content of MgO and K\({}_{2}\)O is higher in clay rocks. The content of other macroelements was low, mostly less than 0.20 wt.%. In a lateral comparison, the Al\({}_{2}\)O\({}_{3}\) and SiO\({}_{2}\) contents in the bauxite of both profiles were comparable. However, the Jinyu profile showed higher levels of TFe\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), MgO, K\({}_{2}\)O, and CaO than those in the Jinshi profile, indicating that the bauxite in the Jinyu profile is of relatively higher quality. Moreover, in the Jinshi profile, the Al\({}_{2}\)O\({}_{3}\) content in the top and bottom layers of the bauxite exceeded 45.00%, while the TFe\({}_{2}\)O\({}_{3}\) content was below 2.00%, suggesting good metallogenic potential. In a vertical comparison, the trends of Al\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), TFe\({}_{2}\)O\({}_{3}\), MgO, and K\({}_{2}\)O were similar (Figure 7).