Avaliação da variabilidade geoquímica de elementos de terras raras, urânio e tório em perfis regolíticos/lateritizados em rochas do complexo jequié Bahia, Brasil

Abstract

The most common rare earth economic mineral deposits are associated with cacialcaline to alkaline magmatic rocks and their products of the weathering. In this work, we present data from drilling conducted in rare earth mineralized weathered rocks from Jequié Complex, in Brazil. These rocks were subjected to intense weathering process, similar to what occurred in the Ion Adsorption Clays deposits in southern China. The data analysis allowed the classification of rare earth mineral resources with similar levels, sometimes higher than those of the Chinese deposits, contained in the lateritic regolithic profile studied. The chemical index of alteration (CIA) was adopted as a classification tool, horizontally separating the mineralized weathering profile into six zones. The data indicated that there was a supergenic enrichment of the REO in the lower portions of the profile and sometimes in the upper zones. The REO average content ranged from 0.09% to 0.22% with maximum of 1.6%. The Th and U elements tended to increase concentrations in the upper portions of the weathering profile, mainly associated with laterization and high leaching zones. Based on the established lithochemical classification, correlation matrices were designed to help define the possible phases of rare earth occurrence in the weather profile. A model section representing the rare earth mineral deposit of supergenic origin in rocks from Jequié / BA Complex was developed.