Electrical Characterization and Mineralogical Differentiation of a Weathering Cover in the South Cameroon Humid Intertropical Zone using the Self-potential Method

Abstract

The study presented herein highlights the existence of a diversity of spontaneous sources of electric potential in weathering cover within the inter-tropical humid zone of south Cameroon. The study site presents a spatial mineralogical heterogeneity, which reveals the dominance of gibbsite more generally upslope, transitioning to a residual kaolinite downslope. The spatial characterization of these weathering mantles at the site revealed a general negative correlation between self-potential (SP), elevation, and sand and silt contents, confirming the existence of a dominant SP electrokinetic source. The main electrokinetic source is attributed to the presence of gibbsite, an abundant mineral at well drained relief summits of intertropical landscapes, likely resulting from the intense alteration of kaolinite. The electrofiltration phenomena related to fluid flow in the gibbsitic summit, quite rich in sand and silt, might justify this origin. A separate SP survey carried out in the kaolinitic mantles 5 km away, which lacked gibbsite, but was richer in clay, revealed a positive correlation between SP, elevation, and clay content of the surface horizons. The difference in correlation is attributed to the electrochemical nature of the SP within the second site. Thus, the diversity of sources of SP gives way to formulation of hypotheses on mineralogical differentiation and spatial characterization of lateritic covers.