The Influence of the Magmatic to Postmagmatic Evolution of the Parent Rock on the Co Deportment in Lateritic Systems: The Example of the Santa Fé Ni-Co Deposit (Brazil)

Abstract The Santa Fé Ni-Co deposit is a major undeveloped lateritic located in the Goiás State of Central Brazil. comprises two properties that together have indicated resources 35.7 million tonnes (Mt), grading 1.14% Ni and 0.083% Co, inferred 104.3 Mt at 1.03% 0.054% Co. laterite was derived from Late Cretaceous alkaline ultramafic lithologies experienced an initial silicification Eocene to Oligocene, followed by lateritization partial reworking Miocene-Pliocene. characterized both oxide- phyllosilicate-dominated ore zones. In former, Ni- Co-bearing hematite goethite dominate supergene mineralogical assemblage, while ore-bearing Mn oxyhydroxides occur as minor components. horizons Ni-carrying phase chlorite. Multivariate statistical analyses (factor analysis principal components analysis) conducted on drill core assay database (bulk-rock chemical analyses) showed significant differences exist between Co distributions. distribution not controlled any clear geochemical correlation. This because highest concentrations been measured ferruginous ochre saprolite zones, where Ni-bearing minerals (chlorite goethite) are mostly associated with reworked material only limited way, zones affected situ ferrugination. Cobalt has atypical if compared other laterites, correlated but also Cr majority facies. From microchemical several potential minerals, it found Co-Cr association related elevated contents residual spinels, representing unweathered phases original parent rock now included laterite. element for deposits, normally oxyhydroxides. case laterite, concentration spinels likely magmatic postmagmatic processes before lateritization, specifically (1) orthomagmatic enrichment chromite, due its high affinity melts, (2) trace elements (i.e., Mn, Ni, Zn) redistribution during hydrothermal alteration chromite into ferritchromite. represents good example how prelateritic evolution strongly affects efficiency mobilization alteration. Based interpretation metallurgical test work, fraction total 20 50% locked spinels.