Caracterização de material laterítico do Planalto e Chapada dos Guimarães – MT por EDX, XRD e Espectroscopia Mössbauer

Abstract

A large portion of the Earth's surface, particularly in tropical regions, is covered with thick lateritic variable formations. In Brazil, the occurrence of laterits is quite widespread, being more developed in the region of tropical/subtropical environment of the country. The study of these formations has great interest to several areas of knowledge, contributing to the understanding of geomorphological and pedological local/regional evolution and for the process of Genesis of associated mineral deposits. In this work, were characterized ferruginous concretions of the plateau region and Chapada dos Guimarães by x-ray Diffraction, x-ray Fluorescence and Mössbauer Spectroscopy, in an attempt to obtain information about its genesis and evolution in terms of geomorphological conditions. Chemical analyses made it possible to highlight important variations between the profiles of each point studied and, also, between sectors of the profiles from the same point, a fact referenced in the text the particularities of each situation in which occur the lateritic formations in the region. Considering the results obtained in this work the authors point out the existence of at least two vertical iron transport types: (i) the descendant, from the cover material to the laterite profile, through the dissolution of iron surface by chemical weathering caused by the increased presence of rainwater and also the (ii) ascendant, from the weathering of the rock underlying the laterite profile, through the fluctuation of groundwater level. The data also do not eliminate the possibility of lateral transport of iron in solution. Consequently, the training model proposed here is actually a mixed model between models of oscillation of the water table and pedogenic.