Provenance and weathering conditions of the Moloundou swamp sediments, southeast Cameroon: Evidence from mineralogy and geochemistry

Abstract

This work reports the mineralogical and geochemical characterization of the Moloundou swamp sediments in order to deduce their tectonic setting, source rock composition, weathering conditions and maturity. These sediments show sandy to loamy sand in nature; they are pale olive to greenish and contain organic matter in the top. Their mineralogy consists of quartz and clay minerals with small amounts of mica, rutile, anatase and feldspars. Tectonic discrimination diagrams and plots of K2O/Na2O vs. SiO2, and TiO2 versus Zr, intermediate sedimentary provenance, within active continental margins in a collisional setting. The A–CN–K ternary diagram points to a high degree of chemical weathering of the source area. The increased plagioclase index of alteration (PIA) values point to a high leaching of plagioclase feldspars during source weathering and transport. The chemical index of alteration (CIA) and the chemical index of weathering (CIW) values for the studied samples suggest a highly intensive chemical weathering in a humid warm climate. The strong chemical weathering of the source rocks is revealed by the presence of kaolinite, goethite and gibbsite. The Moloundou swamp sediments are tectonically in an active setting, derived from mixed acid to intermediate magmatic and metamorphic source rocks.