GEOCHEMICAL-EXPLORATION OF THE MAICURU ALKALINE-ULTRAMAFIC-CARBONATITE COMPLEX, NORTHERN BRAZIL

The Serra do Maicuru represents an alkaline-ultramafic-carbonatite complex, emplaced in the Guiana Craton, which developed a thick lateritic profile, enriched in aluminum phosphates and especially titanium mineralization. The most important parent rocks are pyroxenites and syenites, plus some isolated apatitic bodies, glimmerites and carbonatite veins that cut all of these rocks. Above this lateritic cover and on its neighborhood, a geochemical survey was carried out by Docegeo, a subsidiary of Companhia Vale do Rio Doce (CVRD). From the surficial laterites, divided into a ferruginous crust and lateritic soil, more than 1500 samples were collected, covering all of the Maicuru structure. They were analyzed for Fe2O3, P2O5, TiO2, Mn, Ni, Co, Cr, Cu, Pb and Zn, including some analyses for REE and Nb. Strongly anomalous phosphorus in soils and in iron crust, as aluminum phosphates, furnished a good guide to primary apatite mineralizations, and showed the presence of high titanium as anatase, ilmenite and titanomagnetite and interesting anomalous amounts of Nb, Cu and REE. The geochemical data also helped identify and delineate the distribution of the main parent rock types.