Iron oxides in soils of different lithological origins in Ferriferous Quadrilateral (Minas Gerais, Brazil)

Abstract

Different environmental conditions also lead to the formation of different pedogenic iron oxides, influencing soil chemistry. We examined the chemistry and mineralogical composition including various crystallographic parameters of pedogenic iron oxides of soils developed from itabirite, ferruginous dolomite, serpentinite and other parent materials. The low SiO2 contents relative to Al2O3 and Fe2O3 suggest strong desilication by the effect of the environmental conditions for all soils. The main pedogenic iron oxides were hematite and goethite, followed by maghemite. The small crystal size of goethite resulted in an increased specific surface area; also, isomorphic substitution of aluminum in goethite differed with the parent material. The highest content of soil Fe2O3 from sulfuric acid digestion found here was 701 g kg− 1, which was the highest value registered in the world literature with this methodology, according to the author's knowledge. The Fed content in the soils was strongly influenced by the parent material, with hematite being the more abundant iron oxide. Al-substitution indicated that hematite formation occurred in a different pedoenviroment than for goehtite. These results suggest that the effects of parent material on soil properties are important for both well weathered soils and little-leached soils, determining their drainage, P adsorption and capacity of trace element accumulation.