Laterite formation under tropical weathering: A geochemical characterization

Abstract

The laterite deposits of the Madayippara in Kannur district, Kerala, is a flat-topped lateritic plateau in Western margin of India.  This study employed geochemical techniques—such as CIA and correlation coefficient analysis—to assess relative weathering and lateritization processes across the selected profile. It is observed that SiO2 and Al₂O₃ are the most abundant oxides in the samples. Fe₂O₃ values suggest strong ferruginization (lateritization) in the upper part of the profile and a corresponding depletion in silica, while the bottom layer exhibits lower Fe₂O₃ content and higher silica levels. The degree of lateritization systematically illustrates samples from various depths according to lateritization intensity, with even the lowest sample falling within the weakly lateritized field. The Weathering Index of Parker (WIP) and Chemical Index of Alteration (CIA) suggest intense tropical weathering leading to the formation of laterites associated with gibbsite-rich layers. The correlation coefficient matrix between different major elements indicates a negative correlation between Fe and Si, reflecting a typical trend in high-grade laterites. Mineralogical studies confirmed the presence of kaolinite, gibbsite, goethite, hematite, and quartz typical of mature laterite profiles. These findings highlight the impact of prolonged tropical weathering on the Madayippara landscape and contribute to a better understanding of the region's geological evolution and resource significance. This study also supports in situ field evidence, indicating that the laterites at Madayippara developed over Tertiary sedimentary rocks during the post-Warkalli lateritisation cycle.