A Metallogenic Evolution Model for the Lead-Zinc Deposits of the Meso and Neoproterozoic Sedimentary Basins of the São Francisco Craton, Bahia and Minas Gerais, Brazil

Misi, Aroldo; Iyer, Brijesh; Coelho, Carlos Eduardo Silva; TASSINARI, COLOMBO C.G.; Franca-Rocha, Washington; Gomes, Adriana S. Rocha; CUNHA, IONÁ ABREU; TOULKERIDIS, TEOPHILOUS; Sanches, Andreia Lima

doi:10.25249/0375-7536.2000302302305

Cited by 23 publications

(25 citation statements)

References 6 publications

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“…However, for deposition in Congo, Hoy and Ohmoto (1989) suggested that the high positive d 34 S values originated from an input of hydrothermal sulphur characterized by a d 34 S $ +9&. The same hypothesis is also proposed for the Meso-and Neoproterozoic lead-zinc deposits of the São Francisco Craton (Misi et al, 2000). Rare d 34 S sulphate analyses from host rocks are $+17& at Mufulira in Zambia (Sweeney et al, 1986) and +22.6& in the Mines Subgroup (average) at Kolwezi (Okitaudji, 1989).…”

Section: Isotopic Geochemistrymentioning

confidence: 77%

“…However they show a consistent large range of d 34 S values (Jensen and Dechow, 1962;Dechow and Jensen, 1965;Sweeney et al, 1986;Okitaudji, 1989;Hoy and Ohmoto, 1989;McGowan et al, 2003;Lerouge et al, 2004), from high negative to high positive values, which characterize the sediment-hosted deposits (e.g. Ohmoto and Rye, 1979;Krouse, 1980;Misi et (Sweeney et al, 1986). +17.0 Fig.…”

Section: Isotopic Geochemistrymentioning

confidence: 92%

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Genesis of sediment-hosted stratiform copper–cobalt deposits, central African Copperbelt

Cailteux¹,

Kampunzu²,

Lerouge³

et al. 2005

Journal of African Earth Sciences

204

158

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Section: Isotopic Geochemistrymentioning

confidence: 77%

Section: Isotopic Geochemistrymentioning

confidence: 92%

Genesis of sediment-hosted stratiform copper–cobalt deposits, central African Copperbelt

Cailteux¹,

Kampunzu²,

Lerouge³

et al. 2005

Journal of African Earth Sciences

204

158

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“…The Morro Agudo lead-zinc mine has reserves at 5 Mt of 6.3% Zn and 2.9% Pb . This deposit has been categorized as a MVT deposit by and Iyer et al(1992); a SEDEX by Misi et al (1996) as well as Freitas-Silva and Dardenne (1997); and an Irish-type by Cunha et al (2000), , Misi et al (2000), and Monteiro (2002).…”

Section: Morro Agudo Lead-zinc Minementioning

confidence: 99%

Geology, mineralogy, and geochemistry of the Vazante Northern Extension zinc silicate deposit, Minas Gerais, Brazil

Slezak

Olivo

Oliveira³

et al. 2014

Ore Geology Reviews

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The Vazante Northern Extension is a continuation of the structurally controlled, hypogene nonsulfide zinc deposit from the Vazante Mine, Minas Gerais, Brazil. The deposit is hosted in Neoproterozoic carbonates of the Serra do Poço Verde Formation located in the Brasília Fold Belt along the western margin of the São Francisco Craton. The Northern Extension deposit is hosted within a shear zone that strikes 200 to 225 and dips 30º-70º NW and is associated with substantial folding that occurred in the same deformation (D 2 ) event and later transcurrent faulting. The shear zone is composed of a tectonic-hydrothermal breccia that can be subdivided into four types:Type 1 Breccia-distally located from the willemite (Zn 2 SiO 4 ) ore, weakly brecciated dolostone with some Fe-carbonate alteration; Type 2 Breccia-Strong Fe-carbonate alteration, intense brecciation; Type 3 Breccia-hematite replacement breccia, usually proximal to the Type 4 Breccia; Type 4 Breccia-willemite ore breccia, containing three generations of hypogene willemite (Zn 2 SiO 4 ) as well as hematite (Fe 2 O 3 ), and franklinite (ZnFe 2 O 4 ). In the southern part of the deposit, late sulfide-rich veinlets are observed cutting the hypogene zinc silicate mineralization, and contain galena, sphalerite, native silver, covellite, and stromeyerite (Cu 1-x Ag 1x S). Geochemical studies conducted on the tectonic-hydrothermal breccia showed a strong regional signature enriched in Ag, Cd, Pb, and Zn. The presence of willemite as opposed to sphalerite and the ubiquity of hematite suggest that the zinc silicate mineralization has formed from the mixing between a low sulfur, acid, oxidizing metalliferous basinal brine similar to the fluids found in MVT deposits with a cooler, more oxidizing, meteoric fluid.iii

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“…(1992) have interpreted to indicate a mineralization age of 650 ± 50 Ma. Lead isotope data also indicate that lead in the deposits of the Vazante–Unaí trend was derived from very uranium‐ and thorium‐rich source rocks, and that isotopic compositions of the Vazante deposit resemble those of much of the Morro Agudo deposit, indicating a possible genetic relationship (Misi et al . 2000; Cunha et al .…”

Section: Geological Backgroundmentioning

confidence: 99%

Numerical modeling of hydrothermal zinc silicate and sulfide mineralization in the Vazante deposit, Brazil

Appold

Monteiro

2009

Geofluids

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The Vazante zinc deposit in central Brazil is currently the world's largest known example of a hypogene nonsulfide (i.e. willemite-dominant) zinc deposit. The mineralization is hypothesized to have formed as a result of mixing between a hot, acidic, reducing, metal-rich brine and a cool, more basic and dilute, metal-poor meteoric fluid. The present study sought to investigate this scenario by quantifying the individual effects of temperature, pH, salinity, and oxidation state on willemite and sphalerite solubility, and modeling their combined effects during mixing through reaction path and reactive transport modeling. Solubility calculations showed that in an initially hot, moderately acidic, reducing, metal-rich ore fluid saturated with respect to silica, willemite solubility is relatively insensitive to changes in temperature and log f o2 , but highly sensitive to changes in pH and salinity. In contrast, sphalerite solubility was highly sensitive to changes in temperature and log f o2 , as well as salinity, and was less sensitive than willemite to changes in pH. Reaction path models sought to extend these observations by modeling the geochemistry of mixing. The results show that mixing is able to produce most of the major zinc ore and gangue minerals observed in the field, though not necessarily at the same paragenetic stages, and that both compositional and temperature changes from mixing are needed. Reactive transport models were formulated to investigate spatial patterns of mineralization. The results showed that sphalerite deposition was strongly controlled by temperature and concentrated in the regions of greatest temperature change. Willemite deposition was concentrated along the interface between the metal-rich ore fluid and the surrounding meteoric fluid. The more rapid transport of solute than heat, in conjunction with the higher concentration of silica than sulfide in both fluids meant that willemite mineralization developed over a broader region and in greater concentrations compared with sphalerite.

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A Metallogenic Evolution Model for the Lead-Zinc Deposits of the Meso and Neoproterozoic Sedimentary Basins of the São Francisco Craton, Bahia and Minas Gerais, Brazil

Cited by 23 publications

References 6 publications

Genesis of sediment-hosted stratiform copper–cobalt deposits, central African Copperbelt

Genesis of sediment-hosted stratiform copper–cobalt deposits, central African Copperbelt

Geology, mineralogy, and geochemistry of the Vazante Northern Extension zinc silicate deposit, Minas Gerais, Brazil

Numerical modeling of hydrothermal zinc silicate and sulfide mineralization in the Vazante deposit, Brazil

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