*2.1.1 The petrographic study*

Several field trips were made. They made it possible to describe rock outcrops, take rock samples and take the coordinates of the various samples. These samples were then described and labeled. In the laboratory, the coordinates of the various rock sampling points were plotted on the topographic map of the study area. Through these different points and the macroscopic description of the samples, a geological map is produced [33]. In order to complete the macroscopic study of the rocks, thin sections of samples were taken at the University of Orleans and the University of Paris-Sud (Orsay Campus) in France. These thin sections were studied with the polarizing microscope of the Laboratory of Environmental Geology of the University of Dschang and at the Laboratory of Life and Earth Sciences of the University of Maroua. Some samples were analyzed with microprobe also at the University of Orleans and the University Paris-Sud (Orsay Campus) and in Nancy for the nomenclature of rock minerals and the determination of the nature of rocks. These microscopic and chemical studies have made it possible to refine the geological map of the caldera of the Mount Bambouto [33]. In addition, some complementary geochemical analyses were made to determine the chemical nature of different lavas.
