Weathered, Ni-sulfide ore-hosting and barren serpentinites in the Fortaleza de Minas greenstone belt, Minas Gerais, Brazil: A rock geochemical study

Oostindiër, Jaap; Vriend, S.P.; Huijsmans, J.P.P.; Taufen, P.M.

doi:10.1016/0009-2541(90)90116-o

Cited by 1 publication

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“…At present, we do not have a reasonable explana tion for this observation. In their study of the Fortaleza de Minas ores, Oostindier et al (1990) showed that: (1) Ni mineralization is associated with Fe-Cr-Ti enriched ultramafics, (2) there is no distinct Ni depletion in the Ni sulfide-bearing serpentinites compared to the barren ones, and (3) the ore-bearing serpentinite has 0.2% S as opposed to 0.04% in barren serpentinites. In our opinion, the lack of Ni depletion reported by these authors contradicts the hypothesis of sulfur assimilation from footwall rocks for the formation of these ores.…”

Section: Discussionmentioning

confidence: 96%

Sulfur Isotopes in Komatiite-Hosted Ni-Cu Sulfide Deposits from the Morro do Ferro Greenstone Belt, Southeastern Brazil

Choudhuri

Iyer

Krouse

1997

International Geology Review

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In the Morro do Ferro greenstone belt in southeastern Brazil, Ni-Cu massive sulfides hosted by komatiites occur in the vicinity of the town of Fortaleza de Minas. Sulfur-isotope abundances were analyzed in sulfides from the main orebody in order to determine the source of the sulfur. The main sulfide minerals in the ore are pyrrhotite (65%), pentlandite (30%), and chalcopyrite (5%). The δ 34 S values of the ores fall within a relatively narrow range, but are slightly higher than values for similar occurrences in other greenstone belts. As there does not seem to be evidence of thermal erosion of country rocks and sulfur assimilation, the heavier sulfur possibly is the result of crustal contamination of the ascending komatiite magma and separation of an immiscible sulfide liquid already at this stage.

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Section: Discussionmentioning

confidence: 96%