ASPECTOS GEOLÓGICOS DOS LATERITOS DA AMAZÔNIA

Abstract (English)

Lateritic rocks are widely found all over the Amazon region. They include mature and immature autochthonous laterites and allochthonous laterites, the latter usually reffered to as stone lines. The mature laterites were formed in the Tertiary, while the immature in the Quaternary. The mature laterites are characterized by well-defined and varied horizon when compared to immature laterite profiles. The parent rocks are of different ages and their petrochemical compositions have given rise to different kinds of laterites. among which the most prominent are the bauxitic, the phosphatic, the ferruginous, the caolinic, the manganesiferous and the nickelliferous. The outtermost cover is called Belterra Clay, a yellow clay material, originated from the lateritic profile weathering. Non-lateritic ironstones are common in the region, sometimes associated with the lateritic profiles. Besides their significant ore potentiality for iron, aluminium, nickel, gold, manganese, phosphates, kaolin, titanium, niobium and REE, laterites are important tools for geochemical exploration, geological mapping and also for geological and geomorphological studies of the evolution of the Amazon region.