Pedogeochemistry of ultramafic soils from the Córrego dos Boiadeiros Body, Quadrilátero Ferrífero, Minas Gerais, Brazil.

Abstract

The Córrego dos Boiadeiros Body (CBB) comprises a metaultramafic-metamafic sequence located in the vicinities of Nova Lima town, central area of the Quadrilátero Ferrífero province. The main rock type is a serpentinite that grades upwards to weathering mantles with well-preserved pedogenetic horizons composed, from bottom to top, of four facies: the R Horizon (Fresh rock facies), the C Horizon (Alterite facies), the B Horizon (Transition facies) and the A Horizon (Solum facies). This article presents the results of geochemical and mass balance studies along a representative pedogenetic profile in order to evaluate the chemical transformations concerning major, trace and Rare Earth Elements. From bottom to top of the selected profile, there is enrichment in Fe2O3, Al2O3 and depletion in MgO and SiO2. There are also relative gains of metallic elements as Ni, Co, V and loss of Au. Cr is enriched at the uppermost horizon. Pt is enriched at the basis of the profile, but decreases towards the upper layers. The weathering mantle is REE-enriched and shows major fractionating of LREE over HREE. In order to evaluate the economic potential of the lateritic deposits, especially concerning Cr content, additional chemical analyses should be distributed over the entire body and its surroundings.