Basic chemical compositions combination rules and quantitative criterion of red beds

Abstract. Red beds belong to slippery formations, and their rapid identification is of great significance for major scientific and engineering issues such as geological hazard risk assessment and rapid response. Existing research often identifies red beds from a qualitative or semi quantitative perspective, resulting in slow recognition speed and inaccurate recognition results, making it difficult to quickly handle landslide geological disasters. Combined with the correlation between red beds geomorphic characteristics, mineral compositions, and chemical compositions, this study established a rapid quantitative identification criterion based on the basic chemical compositions combination rules in the red beds. By collecting chemical compositions data of rocks containing red beds, a total of 241,405 groups data were collected for qualitative and quantitative comparison between multiple sets of chemical composition combinations. The results indicate that simultaneously meeting the following chemical composition combinations can serve as a quantitative criterion for distinguishing red beds from other rocks: SiO₂+Al₂O₃ ≈ 50.7 %~85.0 %, Al₂O₃/SiO₂ ≈ 0.14~0.41, FeO+Fe₂O₃ ≈ 0.9 %~7.9 %, Fe₂O₃/FeO ≈ 1.52~7.70, K₂O+Na₂O ≈ 1.6 %~6.8 %, Na₂O/K₂O ≈ 0.02~0.43, CaO+MgO ≈ 0.8 %~9.2 %. By comparing the chemical composition combinations of 15 kinds of rocks collected from China in this study, it is proven that the quantitative criterion proposed in this study are effective.