Abstract

Study on lateritic profiles in different areas of Việt Nam by modern techniques has been allowing us to identify the nature and origin of the lateritization process. Laterite formations were formed mainly in the upper part of weathering crust, where the secondary kaolinite was accumulated with high porosity. In this part, the iron-aluminium oxide and hydroxide filled up pores or replaced a part of clay. This accumulation is due to the leaching of Si, alkali and alkaline earth, occuring in upper zones and infiltrating down. Therefore, in uppermost zones of weathering profiles the red or reddish-brown, weakly cemented weathered materials are often fine-grained and consist of an association of kaolinite particles, aluminium and/or iron oxide-hydroxide. This process occurs by hypergene metasomatic mechanism and the results led to the geochemical differentiation and created zonation with different compositions and structures in weathering profiles.