Altérations dans la zone tropicale. Signification à travers les mécanismes anciens et/ou encore actuelsWeathering in tropical zone. Significance through ancient and still active mechanisms

The microscopic study of the organization of soils and alterites reveals the direction of evolution and the genetic and historical relationship between their constitutive minerals and how, subsequently, geochemical processes could be visualized. If certain soils and alterites may be considered to be the products of recent weathering, others span a much longer time interval. These different aspects of the weathering mantle coexist in the same landscape, and this situation makes them difficult to distinguish. In other words, the weathering mantle that extends over most continental areas is a real patchwork in search for an equilibrium never reached. So, in lateritic weathering mantles, most of genetic and evolutive modelling reveals the complexity of geochemical processes and time scale required to their differentiation ranges from one to several million years. The weathering rates and ages of weathering profiles are discussed as a function of processes that run at the top and at the bottom of weathering mantles. To cite this article: D. Nahon, C. R. Geoscience 335 (2003).