Controle na distribuição das lateritas e saprolitos de alto teor no depósito de níquel laterítico do Jacaré, Distrito de Carajás, Brasil

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2011

RESUMO

The Jacaré world class nickel lateritic deposit (495Mt @ 1,19% Ni) is positioned about 52 Km NNE straight line from São Félix do Xingu/PA State - Carajás Mineral Province. The deposit occurs in essentially dunitic and gabbroic rocks magmatically layered with subordinated peridotites and pyroxenites levels. The saprolitic zones host the main Ni ores and the serpentine mineral group contain the main Ni grades, where lizardite, antigorite and crisotile with non-pseudomorphic texture (e.g. interpenetrating, interlocking), pseudomorphic (hourglass and minor mesh ) and venulets are the main minerals. However, the participation of oxidized minerals as goethite ( FeO.OH) and hematite ( Fe2O3) in zones of high Ni concentration in saprolites layers is clear, where this element is absorbed and/or adsorbed in the related minerals. As the oxidized minerals rising up in profile, they compose the main mineral assembly, being responsible for Ni fixation in some levels proportionally inverse to environment pH diminution, where the oxidation state do not permit the Ni2+ fixation with Fe3+, which leaves the element mobile in the system. As closer to the surface, in dryer zones of acid character, the oxidation process enrich the system in iron and generate nodules and lateritic covers, evolving to "duricrusts" (south block). The oxi-reduction process is favored by structures, once they permit a free circulation of meteoric waters until the oxi-reduction zone, causing an increasing in Ni links, preferentially in oxide and protho-oxides. However, the so called "garnieritic minerals" previously identified in the deposit, did not repeat their assay results in this thesis, Hence, it discards the possibility of garnierite to be the main high grade Ni- ore, as well clay minerals of smectite group. Beside high grade Ni-ores have been associated with saprolitic zones, which respect the pyrometallurgic route to Fe-Ni production, there are remarkable nickel concentration in oxides and hydroxides in the same level, which can impact directly in pre- calcination and calcination process of material at the plant scale, once the energy consumption used for this activity will be considerably increased causing in additional OPEX expenses. The siliceous laterites and ferruginous laterites did not show divergences in chemical or mineralogical composition when compared to mineral deposits of similar characteristics worldwide, in this way, these ores are able to be inserted in hydrometallurgical routs. The dynamics and consecutive geomorphologic evolution of Jacaré Deposit shows that the area is in clear development of a second relief inversion, where the south portion had an initial mass eroded and nowadays shows the development of "duricrust" where the north portion is passing through dessilicification process, formation a ferruginous levels in oxi-reduction zones with strong relief dissecation.

ASSUNTO(S)

rochas ultramaficas niquel são félix do xingu (pa) fresco, rio (pa) geoquímica

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