Statistical analysis of major element behavior in gneiss weathering profiles, northwest of Yaoundé, South Cameroon

This study investigates the morphological, mineralogical, and geochemical characteristics of weathering profiles developed on garnet and biotite gneisses in the Nguibassal and Maganga areas, northwest of Yaoundé (South Cameroon). The objective was to characterize major element evolution across the profiles and assess their statistical behavior using correlation analysis and Principal Component Analysis (PCA). The two weathering profiles, 4 m thick in Nguibassal and 3 m in Maganga, content four horizons: iron duricrust, nodular, loose clayey, and organomineral horizons. Both profiles display the reddish coloration typical of ferrallitic soils formed under humid tropical conditions. Mineralogy is dominated by quartz, feldspars, and muscovite, with kaolinite, hematite, and goethite, reflecting advanced chemical weathering. Geochemically, soils are aluminous–siliceous with high SiO₂ (50–67 wt%), Al₂O₃ (13–26 wt%), and Fe₂O₃ (5–14 wt%). SiO₂ decreases upward, whereas Al₂O₃ and Fe₂O₃ increase, consistent with progressive desilication and sesquioxide enrichment. The Chemical Index of Alteration (CIA) indicates very advanced weathering in Nguibassal (CIA = 89.5–94.9%) and moderate to high alteration in Maganga (CIA = 69.1–88.7%). PCA performed on standardized data shows that PC1 distinguishes silica-rich phases from Fe–Al oxides, while PC2 separates TiO₂–MnO from K₂O, reflecting mineral transformation pathways, reveals two main components explaining 83.2 % and 89.7 % of total variance at Nguibassal and Maganga, respectively. Despite the small dataset (n = 10), statistical trends confirm stronger ferrallitization in Nguibassal compared to Maganga. These results help clarify the geochemical evolution of gneiss-derived weathering profiles in the humid tropical zone of Cameroon and provide a basis for future regional comparisons.