Comportamento dos Elementos Terras Raras na Alteração Intempérica de Rochas Vulcânicas Ácidas no Sul do Brasil

Resumen

This paper presents the result of a study of the behavior of Rare Earth Elements (REE) in the weathering of acid volcanic rocks (riolites) situated in the southern part of Brazil. Results show a clear loss of all REE in such conditions. The REE amounts decreases from the lower part to the top of the profile. The loss is progressive, increasing as the density become smaller. There are not differences in behavior between light and heavy REE. Little thickness of the weathering crust is the main responsible for the absence of the absolute accumulations in the lower part of the profile of the REE liberated by the rock-minerals decomposition and not fixed to new-formed minerals.