# Provenance and Paleo-Environment of the Late Carboniferous Bauxite Formations in Southern Shanxi
## 4 Result
### 4.3. Geochemical Characteristics of Elements
#### 4.3.2 Trace Elements  
The formation of Shanxi bauxite took place within the metallogenic environment of the NCC, where the attributes of rocks involved are comparable to those of the upper crust [7; 9; 32]. Consequently, this study employed upper crust trace element data to standardize the geochemical data of profile rock samples to analyze the geochemical characteristics of trace elements.  
The test data revealed that in the Jinyu profile, the average Li content was highest in clay rocks (464-732 \(\upmu\)g/g, averaging 580 \(\upmu\)g/g), followed by bauxite ore (314 \(\upmu\)g/g), iron-bearing clays (104-362 \(\upmu\)g/g, averaging 210 \(\upmu\)g/g), and sandstones (31.7-51.3 \(\upmu\)g/g, averaging 46.93 \(\upmu\)g/g) (Table 2). The enrichment factors for Li and Bi in the bauxite are greater than 10 (Figure 8), indicating substantial enrichment (Figure 8). Enrichment factors for U, Th, Cr, Sb, Nb, and Ta ranged from 5 to 10, suggesting moderate enrichment. Sc, Ga, In, W, Pb, Zr, and Hf all had enrichment factors above 2, indicating slight enrichment. In the clay rocks, Li and Bi remain highly enriched, Sb is moderately enriched, and In, U, Th, Pb, Nb, Ga, Sc, and Ta are slightly enriched.  
In the Jinshi profile, the average Li content was highest in aluminum rocks (967-1994 \(\upmu\)g/g, averaging 1480.5 \(\upmu\)g/g), followed by bauxitic ore (915 \(\upmu\)g/g), clay rock (137 \(\upmu\)g/g), sandstones (33.9-76.5 \(\upmu\)g/g, averaging 53.47 \(\upmu\)g/g) and coals (22.6-43.8 \(\upmu\)g/g, averaging 33.2 \(\upmu\)g/g) (Table 3). Li, Bi, and U exhibit significant enrichment within the bauxite, while Cr displays moderate enrichment, and V, Ga, In, Sb, W, Th, Nb, and Ta demonstrate slight enrichment (Table 3). In the clay/aluminous rocks, Li and Bi continue to be highly enriched, U is moderately enriched, and Sc, Ga, In, Sb, Th, Pb, Nb, Ta, Zr, and Hf are lightly enriched, with the highest Li content reaching 1994.00 \(\upmu\)g/g (S7) and an average content of 1032.67 \(\upmu\)g/g.  
In comparison, the bauxite and clay rocks of both profiles exhibit significantly high enrichment levels of Li, Bi, and U, with relatively high enrichment of In, Sb, Th, Nb, and Ta. The Li content is notably higher in the clay/aluminous rocks, whereas the U content is more concentrated in the bauxite. The Jinyu profile shows greater enrichment in Bi, Sb, Th, Nb, and Ta within the bauxite, while the clay rocks exhibit higher enrichment in In. The Jinshi profile's clay rocks are more enriched in In, Bi, Sb, Th, Nb, and Ta. As noted in Section 4.2.2, cookeite was found in the S7 sample (Figure 6b), and boehmite was identified in the Y7 sample (Figure 6e). The Li concentrations in S7 and Y7 are markedly higher than those in other samples (Table 3). S7 and Y7 are located in the upper part of the ore bed, while the underlying substrates S9 and Y9, despite having the same lithology, show significantly lower Li content. This suggests that cookeite and boehmite are likely the primary carriers  
Figure 7: Vertical variation diagram of the main elements in Jinyu and Jinshi profiles. Note: Y1–Y11: Jinyu profile sample numbering, S1–S9: Jinshi profile sample numbering.