Caracterização dos contaminantes do minério de ferro do depósito mineral da Serra do Sapo, Conceição do Mato Dentro, Minas Gerais

Abstract

The itabirites of Serra do Sapo ore deposit are located in the Serra do Espinhaço region and are described as part of the Serra do Sapo Formation, the upper unit of the Serra da Serpentina Group, superposed to the schists and phyllites of the Meloso Formation. Iron formations with a high content of aluminum and phosphorus occur in contact with the schists of the basal unit. These contacts are transitional and generate a rock with millimeter to centimeter levels containing high iron oxide concentration. This lithology has a silky texture and always occurs decomposed, being described as hematite-quartz-mica schists or classified as Itabirite with high content of contaminants (IFX). The classification of itabirites is made according to the degree of weathering of the rock. Banded iron formations classified as Itabirites (IT) that also present high levels of phosphorus as contaminants; are classified as Itabirite with high phosphorus content (ITX). Petrographic studies identified muscovite, chlorite and gibbsite as the main sources of aluminum for IFX samples. The high levels of Al2O3 and P2O5 in these lithotypes are also explained by the supergenic formation process, where the space of the leached minerals is filled by chlorite and gibbsite. For ITX the high levels of phosphorus are related to apatite minerals that occur more frequently in this lithotype. Geochemical data shows that IFX samples, when normalized to PAAS, are enriched in LREE compared to the other itabirites. These samples are also enriched in mobile elements such as Ba and Sr. This indicates that the enrichment is due to the mobility of the LREE in a weathered environment without HREE.