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This study combines the finite element approach and the spectral analysis of Fourier's function, to investigate the eastern Cameroon and western Central African Republic. In this area, the signature of the gravity anomalies seems to correspond to the transition zone between the Congo Craton and the Panafrican Mobile Belt. Thus, a gravity interpretation based on the data obtained from four N-S profiles on the residual map is carried out using a 2.5D model. The residual anomaly map is obtained by using the finite element method (FEM) for data filtering. Spectral analysis is used to estimate the depth of the sources responsible of the observed anomalies. Our results demonstrated that the observed gravity anomalies in the region are associated with tectonic subsurface structures. This study suggests that the transition area, which comprises the northern margin of the Congo Craton (CC) and the southern border of the Mobile Zone of Central Africa (MZCA) known as the Pan-African Belt (area covering the geological Congo Craton limit (GCCL)), is a product of convergent collision. This collision has caused considerable over-thrusting of the Pan-African Belt (PAB) units onto the Congo Craton. The models suggest the intrusion of magmatic rocks during the continental collision, which were later metamorphosed into granulites along and around the northern margin of the Congo Craton. The presence of deep granulite structures in the northern margin of the CC expresses a continental collision. Some sediment formations appear in the Central African Republic with variable thicknesses. The granulites (deeper parts of PAB) observed might come from the uprising of some materials of the upper mantle probably during the opening of the Atlantic Ocean. The probable geophysical limit of the CC in the upper crust is suggested on this study. [ABSTRACT FROM AUTHOR]