# Eocene Sedimentary-Diagnetic Environment Analysis of the Pingtai Area of the Qaidam Basin
## 4 Clay Minerals
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Fm**} & **Burited** & **Quartz** & **Potassium Sodium** & **Calcite** & **Dolomite** & **Hennatic** & \multicolumn{3}{c}{**Total**} & \multicolumn{3}{c}{**Relative Content of Clay**} & \multicolumn{3}{c}{**Mixed Layer**} \\  & **Depth** & **(w\%)** & **Feldspar** & **Feldspar** & **Feldspar** & **(w\%)** & **(w\%)** & **(w\%)** & **(w\%)** & **of Clay** & & **Minerals** (w\%)** & & **Ratio (w\%)** \\ \hline \multirow{4}{*}{**Felcome**} & 644.77 & 15.4 & 0.5 & 3.4 & 16.6 & 23.5 & 2.2 & 36.0 & / & 61 & 22 & / & 17 & 23 \\  & 645.77 & 31.9 & 1.0 & 7.1 & 10.8 & 4.0 & 1.2 & 41.2 & / & 69 & 14 & / & 17 & 63 \\  & 647.76 & 47.5 & 2.3 & 11.2 & 18 & 3.0 & / & 16.4 & / & 76 & 4 & / & 20 & 53 \\  & 648.26 & 26.9 & 1.0 & 6.5 & 22.7 & 10.4 & 1.8 & 28.8 & / & 71 & 13 & / & 16 & 53 \\  & 648.76 & 18.2 & 0.4 & 3.7 & 28.4 & 9.2 & 1.4 & 36.6 & / & 72 & 14 & / & 14 & 56 \\  & 649.76 & 40.7 & 1.4 & 11.7 & 23.9 & 2.5 & / & 17.1 & / & 69 & 14 & / & 17 & 54 \\  & 630.26 & 56.5 & 1.9 & 11.4 & 9.5 & 1.8 & / & 18.0 & / & 69 & 13 & / & 18 & 57 \\  & 651.26 & 42.8 & 0.9 & 8.5 & 27.2 & 3.8 & / & 14.9 & / & / & / & / & / \\  & 652.26 & 42.8 & 1.4 & 9.1 & 20.9 & 3.0 & / & 20.7 & / & 69 & 15 & / & 16 & 56 \\  & 653.26 & 36.8 & 1.3 & 9.4 & 23.2 & 3.5 & / & 23.2 & / & 56 & 29 & / & 15 & 59 \\ \hline \multirow{4}{*}{**Felcome**} & 928.23 & 70.5 & 1.5 & 9.6 & 9.5 & / & / & 7.9 & 77 & / & 11 & / & 12 & / \\  & 929.68 & 60.8 & 6.6 & 15.6 & 4.8 & 1.1 & / & 8.9 & 63 & / & 14 & / & 23 & / \\  & 959.8 & 64.5 & 2.3 & 8.3 & 18.8 & / & / & 4.9 & 74 & / & 13 & / & 13 & / \\  & 997.3 & 67.9 & 3.1 & 12.3 & 8.1 & / & / & 7.9 & 68 & / & 12 & / & 20 & / \\  & 998.28 & 50.3 & 3.1 & 12.3 & 22.9 & / & 9.6 & 34 & / & 21 & / & 45 & / \\  & 1000.88 & 58.8 & 3.8 & 15.8 & 11.2 & 1.0 & / & 7.6 & 32 & / & 28 & / & 40 & / \\  & 1002.28 & 61.5 & 1.6 & 6.4 & 13.1 & / & / & 7.8 & 46 & / & 45 & / & 9 & / \\  & 1002.78 & 57.6 & 2.0 & 13.3 & 8.1 & / & / & 13.0 & 36 & / & 53 & / & 11 & / \\ \hline \hline \end{tabular} Note: Standard: SY/T5163-2018. The reason why S + I/S + I +K + C = 101 or 99 is rounding rather than data bias. According to the relevant standards, I/S with a mixed layer ratio greater than 70% is classified as smectite. Description: S is smectite, I/S is a mixed layer of illite/smectite, I is illite, K is kaolinite and C is chlorite. The mixed-layer ratio (e.g., 20%) indicates that the smectite content in the mixed layer of illite/smectite is 20%.  
\end{table} 
Table 1: X-ray diffraction analysis results of all Eocene rock and clay minerals in the Pingtai area. 20% of the clays with an average content of 16.67%. The content of illite varied greatly, between 4% and 29%, with an average content of 16.67%. Kaolinite is generally considered to form by strong leaching of feldspar, mica and pyroxene in a humid climate and acid medium [4; 29]. A warm and humid climate is conducive to the formation and preservation of kaolinite [30]. Illite is formed in warm or cold climate conditions with little rain and is formed by aluminosilicate minerals, such as feldspar and mica in the case of weathering and removal of K\({}^{+}\)[31; 32; 33]. Therefore, a dry climate and weak leaching are favorable to the formation and preservation of illite [34]. If the climate becomes hot and humid with thorough chemical weathering, illite will gradually decompose into kaolinite [31]. Chlorite is formed in alkaline environments and is unstable under oxidizing conditions; thus, chlorite can generally only survive in areas where chemical weathering is inhibited (such as glaciers or arid surfaces) [35; 36]. Increases in chlorite and illite content are commonly considered to represent climatic conditions that gradually become more arid [37; 38; 39]. Smectite forms easily in a climate with alternating wet and dry conditions [40; 41] and readily forms in salt-rich conditions, especially in alkaline media poor in K\({}^{+}\) but rich in Na\({}^{+}\) and Ca\({}^{2+}\).