A Toposequential Study of Duricrusts Developed on Granite and Gneiss in Meiganga, Adamawa Region: Understanding Lateritic Formations Assessment in Central Cameroon
This study investigates the toposequential development of duricrusts formed on granite and gneiss in Meiganga, in the Adamawa Region of Central Cameroon. The area lies within a tropical upland characterized by duricrust outcrops. The methodology includes field investigations for duricrusts description and sampling for mineralogically and geochemically characterizations. Eleven samples were collected including six on granite and five on gneiss. Four main facies were identified: nodular and massive at both sites, vacuolar exclusively on granite, and brecciated only on gneiss. The study reveals a toposequential differentiation of the duricrusts with high-altitude positions (1150 m) displaying thick and mature duricrusts enriched in goethite and gibbsite, while mid and lower slope sites (1000 - 1050) show less indurated and kaolinite-rich materials. Geochemically, Fe2O3, the most important oxide, varied from 28.62% to 78.79%. It is followed by Al2O3 (3.06% - 32.6%). The SiO2 contents ranged from 0.95% to 22.48%. The alkali and alkaline earth elements are mostly low (0.1%). Most important trace elements identified are Ba (5 - 1191 ppm), V (108 - 1118 ppm) and Zr (9.6 - 529.4 ppm). LREE are more concentrated than HREE: 459.57 ppm and 39.44 ppm for granitic duricrusts; 722.45 ppm and 54.86 ppm for gneissic materials. The high CIA and MIA values (>99) confirm an intense duricrust weathering, leading to clay minerals development through ferruginization, monosialitization, and allitization. These results support a model of lateritic landscape evolution based on topography, lithology, and climatic conditions, which favored the understanding of duricrust processes in general and those of Adamawa region in particular.
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