Lateritic nickel deposits of Brazil

Abstract

Many nickel deposits are known in Brazil, accounting for about 350.106 tons of ore with an average of 1.5% Ni. All are of the lateritic type. These deposits are scattered throughout the country, being rarer in the Northeastern Region and in the South, below 25~ latitude. They are mainly associated with mafic-ultramafic massifs of large dimensions and ultramafic alkaline complexes, and occur in climatic regions of contrasting seasons. The weathering profile developed over the fresh rock consists, from bottom to top, of the following horizons: altered rock, coarse saprolite, argillaceous saprolite, ferruginous saprolite and lateritic overburden. The thickness of each horizon varies from one deposit to another, the whole profile generally exceeding 20 m. The saprolitic horizons with inherited minerals (serpentine, chlorite) or neoformed minerals (smectites) constitute the silicated nickel ore and are thicker were climatic conditions are drier; the ferruginous upper horizons made up of iron oxide-hydroxides are more developed in more humid regions. In Brazil, the silicated ore generally prevails over the oxidized ore. The main Ni-bearing minerals are serpentine, smectite, garnierite and goethite. The latcritic nickel deposits of Brazil may be correlated with two erosion surfaces, corresponding to the Sul Americano (Lower Tertiary) and Velhas (Upper Tertiary) levelling cycles. The degree of dismantling of the higher and more ancient surface and the consequent development of the Velhas Surface control the position of the nickel accumulation in the landscape. Thus, the deposits may be found either in the lowlands or in the highlands, where they are always covered by a silcrete layer. The alteration profiles in the Brazilian lateritic nickel deposits are broadly similar to those described elsewhere in the world. However, they present two characteristic features: the silicated ore prevails over the oxidized ore, and a silicified layer covers the profies developed on the highlands.

Platinum-Group Minerals in Chromitites of the Niquelândia Layered Intrusion (Central Goias, Brazil): Their Magmatic Origin and Low-Temperature Reworking during Serpentinization and Lateritic Weathering

“…Final convergence and continental collision caused deformation and disruption at about 630 Ma [4]. During Lower-Tertiary erosion, corresponding to the Sul-Americano cycle, ultramafic units in the lower part of the intrusion underwent supergene alteration and weathering originating in a thick laterite cover with silicate-Ni deposits [5].…”

Ni grade distribution in laterite characterized from geostatistics, topography and the paleo-groundwater system in Sorowako, Indonesia

“…This structure suggests a possible occurrence of isomorphous substitution of Fe 3+ , placed at the center of octahedral coordination, by the other cations such as Ni (Zeissink, 1969;de Oliveira et al, 1992;Alvarez et al, 2008). According to a bulk chemical analysis (Golightly and Arancibia, 1979), most irons in the weathered serpentines were found as ferric.…”

“…Many studies have been devoted to understanding the enrichment processes of Ni in laterite deposits, taking the host rock and mineral composition and their influence on supergene Ni products into account (Colin et al, 1990;de Oliveira et al, 1992;Proenza et al, 2008;Talovina et al, 2008;Thorne et al, 2009;Gallardo et al, 2010;Alevizos and Repouskou, 2011;Sagapoa et al, 2011). Other important observations on Ni grade distribution have been made, such as enrichment from the weathering of serpentine minerals (Zeissink, 1969), Ni grade correlation with other metals (Co, Cr, Al, and Fe) concentrated in the residue of laterites (de Vletter, 1978) and the existence of mineralized veins causing high Ni grades (Dowd, 1992).…”

“…Meteorological conditions have also been identified as a key factor in Ni enrichment (de Oliveira et al, 1992;Lewis et al, 2006;Herrington et al, 2007;Thorne et al, 2012).…”

Gênese e controles da mineralização secundária de P, Ti e ETR no complexo alcalino carbonatítico de Salitre, MG

“…Concentrações locais de Si são interpretadas como resultado da remoção parcial deste elemento do sistema em um ambiente de drenagem restrita, processo relativamente comum em lateritas geradas a partir de rochas empobrecidas em Al (Oliveira et al, 1992 (Imbernon et al, 1994;Morteani e Preinfalk, 1996;Oliveira e Imbernon, 1998). As zonas silicificadas muito ricas em ETR podem ser resultado combinado de contribuição hipogênica e também supergênica Oliveira e Imbernon, 1998).…”