versão impressa ISSN 0103-9016
COELHO, Maurício Rizzato e VIDAL-TORRADO, Pablo. Cerium (Ce) in some nodular ferricretes developed in soils of the adamantina formation. Sci. agric. [online]. 2000, vol.57, n.2, pp. 329-336. ISSN 0103-9016. http://dx.doi.org/10.1590/S0103-90162000000200021.
The observation of rare earth element (REE) accumulations, especially Ce, has led to an open discussion about the genesis of lateritic weathering systems. In the landscape of the northern State of São Paulo (Brazil), lateritic covers predominantly nodular exist in different topographic levels and, although not documented, constitute a feature that appears frequently on the slopes of Cretaceous sandstones of the Adamantina Formation (Ka). In order to obtain subsidies for the understanding of the genesis and the spatial distribution of these features, the objective of this research was to verify the presence and the form of occurrence of REE, in nodular ferricretes of an Eutric Plinthosol. Submicroscopic studies and microprobe analyses were performed on undeformed samples of Fe and Fe-Mn nodules. These were previously identified in morphological descriptions (macro and micro) of petroplinthic horizons located at the footslope of a toposequence. Cerium, iron and manganese were determined by X ray fluorescence, and iron and manganese were also determined by selective dissolution. Localized accumulations of Ce were found only into petroplinthic nodules with Mn coatings, probably deposited during the definitive lowering of the water table. Ce and Co accompanied the mobilization and segregation of the Mn oxides and hydroxides due of the ability of these Mn species in concentrating and controlling the distribution of certain metallic ions.
Palavras-chave : laterite; petroplinthite; plinthite.