GEOQUÍMICA DO PERFIL LATERÍTICO DE OUTEIRO (BELÉM-PARÁ)

Abstract

The Amazon region has, in all its immensity, abundant occurrences of laterites. These laterites, a product resulting from subaerial tropical weathering processes, keep records and important information about the environmental transformations experienced by the region. The Outeiro Island, inserted in this context, presents in its cliffs, good exposures of this lithological type. In this work these laterites are described as a function of the texture, closely related to the granulometry of the Barreiras Sediments, involved in the lateritization process. In them, the soil horizons, concretionary, mottled and remains of the mother rock and/or substrate are identified. The predominant mineralogy in the horizons in this profile is quartz and kaolinite, occurring in the concretionary horizon a large amount of hematite and goethite and muscovite in the most basal portion. The heavy minerals identified were, in order of abundance, staurolite, tourmaline, kyanite, zircon and rutile. The chemistry is characterized by high levels of SiO2, ranging from top to bottom from 90% to 51% and high levels of Fe and Al in the concretionary horizon and of Fe in the bedrock, not characterizing, however, a complete chemical differentiation, proving the immature nature of the profile. Keywords: Soils; concrecionary; mottled; kaolinite; hematite.