A chemical model for the concentration of gold in volcanogenic massive sulphide deposits

Huston, David L.; Large, Ross R.

doi:10.1016/0169-1368(89)90017-6

Cited by 139 publications

(64 citation statements)

References 31 publications

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“…Gold associated with the sulfides was probably transported as AuCI-2 , in a high-temperature, relatively oxidized fluid acid, where precipitation occurs due to an increase of the pH, a decrease of the f0 2 or of the activity of CI-and a decrease in temperature (Huston & Large, 1989), in the same way as it occurs in the highest levei of the exhalative process in the oceanic floor.…”

Section: Cordierite-anthophyllite Rocksmentioning

confidence: 99%

Estudo De Inclusões Fluidas Em Mineralização Sulfetada Vulcanogênica Hidrotermal E De Ouro Orogênico Na Serra Do Ipitinga, Amazônia, Brasil

Faraco¹,

Fuzikawa²,

Ramboz³

et al. 2006

RBG

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Resumo ESTUDO DE INCLUSÕES FLUIDAS EM MINERALIZAÇÃO SULFETADA VULGANOGÊNICA HIDROTERMAL E DE OURO OROGÊNICO NA SERRA DO IPJTJNGA, AMAZÔNIA, BRASIL aGrupo Ipitinga (2,27 Ga), na serra homôni-ma, consiste em uma unidade metavulcanossedimentar, constituída por metavu1cânicas máficas e ultramáficas, rochas a cordierita-antofilita e a quartzo-clorita, às quais estão sobrepostos metassedimentos químicos (BIFs tipos óxido e silicato) e elásticos, Parte das lavas básicas foi hidrotennalmente alterada em condições similares às de sistemas hidrotermais atuais, ao longo dos eixos de expansão oceânicos, formando rochas a quartzo-clorita e mineralizações sulfetadas do tipo vu1canogênico hidrotermal sindeposicional, constituídas de pirrotita, pirita, ca1copirita, esfalerita, com ouro e prata associados, além de traços de galena, molibdenita e telureto de prata. Toda a unidade vu1canossedimentar foi deformada por cisalhamento rúptil-dúctil,assumindo a atual configuração estrutural de cinturão de cisalhamento NW-SE, com mergulhos subverti cais, geralmente para NE. Durante esse episódio, os fluidos hidrotermais originaram veios de quartzo auríferos. Doze tipos de inclusões fluidas identificadas no Grupo Ipitinga, discriminam dois sistemas de fluidos relacionados a três eventos hidrotermais peculiares. As rochas a quartzo-clorita (basaltos hidrotermalmente alterados), as principais hospedeiras das mineralizações sulfetadas, contêm onze tipos de inclusões fluidas. Oito deles ocorrem exclusivamente nessas rochas, geradas a partir de reações fluido-rocha durante o primeiro evento hidrotermal (1). Esse evento envolveu um fluido aquo-carbônico consistindo principalmente de CH 4 e Hp, com traços de N 2 e H 2S. Inclusões de CO 2 com traços de CH 4 H 2S e N 2 , são subordinadas. A predominância de CH 4 sobre CO 2 no sistema de fluido aquo-carbônico, é coerente com os modelos propostos para a geração de mineralizações sulfetadas vulcanogênicas exalativas nos sistemas hidrotermais de dorsais meso oceânicas. A presença de CH 4 nas rochas resultantes do primeiro evento hidrotermal no Grupo Ipitinga, evidencia a ação de um processo metamórfíco-hidrotemal em um ambiente similar aos atuais centros de expansão. Os valores de temperatura e pressão calculados para a geração da mineralização sulfetada no Grupo Ipitinga compreendem os intervalos de 250-450°C e 0.7 -2.3 kbar, respectivamente. Fluidos aquosos salinos relacionados ao segundo evento hidrotermal (II) ocorrem somente nas rochas a cordierite-antofilita. Os veios de quartzo originados em um terceiro evento hidrotermal (III) , relacionado ao cisalhamento dúctil, contêm inclusões de um fluido aquoso salino que pode também ser encontrado em quartzo das rochas a quartzo-clorita. Além dos dados acima apresentados, o estudo das inclusões fluidas também indicou uma cronologia relativa para os eventos metamórfíco-hidrotermais no Grupo Ipitinga.Palavras-chave: inclusões fluidas, sulfeto, ouro, metano, sistema hidrotermal AbstractThe Ipitinga Group (2.27 Ga) at the Serra do Ipitinga consists of a met...

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Section: Cordierite-anthophyllite Rocksmentioning

confidence: 99%

Estudo De Inclusões Fluidas Em Mineralização Sulfetada Vulcanogênica Hidrotermal E De Ouro Orogênico Na Serra Do Ipitinga, Amazônia, Brasil

Faraco¹,

Fuzikawa²,

Ramboz³

et al. 2006

RBG

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“…4A, B). Formation of cinnabar, Ag-sulfides, and sulfosalts from reduced percolating fluids associated with those reduced lithologies involved desulfurization in the Au-bearing solutions (Huston and Large, 1989;Williams et al, 2009). Therefore, these processes resulted in the destabilization of the aqueous Au 1+ -sulfur carrier complexes and the formation of medium-fineness and subrounded Au grains (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…This mineral paragenesis (siderite ± galena within the gossan, and cinnabar + Ag-sulfosalts within fault breccias in the cementation zone) involves a reducing solution and (bio)sulfur reduction, which constrains the role of thiosulfate complexes as the only mobilization mechanism throughout the supergene profile. In zones where solutions were more reducing, thiosulfate complexes could have been reduced to bisulfide complexes due to their high solubility under low oxygen fugacity and near neutral conditions, as well as in equilibrium with pyrite (Stroffegen, 1986;Webster, 1986;Huston and Large, 1989;Renders and Seward, 1989;Vlassopoulos and Wood 1990;Benedetti and Boulegue, 1991;Gray et al, 1992;Tagirov et al, 2006). Furthermore, late-vertical fault systems acted as high permeability conduits driving the Au-Ag-enriched basinal fluids, with precious metals thiosulfate and/or bisulfide complexes as stable compounds in solution, until reaching the cementation zone (Fig.…”

Section: Discussionmentioning

confidence: 99%

Gold Behavior in Supergene Profiles Under Changing Redox Conditions: The Example of the Las Cruces Deposit, Iberian Pyrite Belt

Yesares¹,

Aiglsperger²,

Sáez³

et al. 2015

Economic Geology

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The Las Cruces deposit is in the eastern end of the Iberian Pyrite Belt (SW Spain). It is currently being mined by Cobre Las Cruces S.A. The main operation is focused on the supergene Cu-enriched zone (initial reserves of 17.6 Mt @ 6.2% Cu). An Au-Ag-Pb-rich gossan resource (3.6 Mt @ 3.3% Pb, 2.5 g/t Au, and 56.3 g/t Ag) occurs in the upper part of the deposit. The Au grade ranges from 0.01 ppm to >100 ppm, and occurs as three different Au ore types: (1) Au mineralization in the upper part of the gossan linked to Fe-oxides lithofacies, (2) Au concentration in the lower part of the gossan associated with leached black shales, and (3) Au ore in the cementation zone related to subvertical fractures.A hydroseparation device has been used to obtain heavy mineral concentrates from selected samples of different ore types. Reflected-light microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and electron probe microanalysis (EPMA) were used to study the separated Au particles. Significant differences between the defined ore types include the Au-bearing lithologies, mineral associations, textural features, particle sizes, morphologies, and fineness. Au-rich minerals include native Au, Au-Ag electrum, and Au-Ag-Hg amalgams. Gold-bearing mineral associations include Pb-oxihalides, Fe-oxides, galena, pyrite, cinnabar, and Ag-sulfosalts.The Au enrichment mechanism in the supergene profile involves (1) dissolution of Au from the primary sulfides as chloride-rich ionic complexes during the weathering of the deposit under subaerial exposure; dissolved Au is transported downward through the supergene profile under acidic and oxidized conditions; (2) destabilization of the Au complexes by Fe-controlled redox reactions; as a consequence, coarse-grained, high-fineness Au particles precipitated in association with Fe-oxyhydroxides. This resulted in secondary concentration in the upper gossan; and (3) after deposition of cover sediments took place a progressive change in the system conditions resulting in a later Au remobilization as hydroxidehalide, hydroxide, thiosulfate, and bisulfide complexes in the lowermost gossan and cementation zone. The main pathways for migration of enriched fluids to the cementation zone are secondary permeability zones linked to Alpine reactivated faults. Deposition of Au seems to be related to fluid interaction with reductant lithologies, including black shales and the primary sulfides.

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“…Gold values show positive correlations with Cu, Zn, Ag and Pb and all together classify Cerro de Maimón as a nonauriferous/base-metal VMS deposit (Poulsen and Hannington, 1995). As summarized by Hannington and Scott (1989), Huston and Large (1989) and Huston et al (1992), in modern massive sulfide-forming systems, Au is commonly transported as Au(HS) 2 − complexes, Au solubility and transport being favored at low temperatures (<300 ºC) and near neutral pH; gold subsequently precipitates upon mixing with seawater by oxidation (above the HSO 4 − -H 2 S equal activity curve), a drop in temperature (<150 ºC) and dilution of H 2 S. The starting composition of the hydrothermal fluid can further complicate the system. Enrichment in Au (not related to high-sulfidation-VMS systems, Hannington et al, 1999b) may also reflect processes such as seafloor boiling or contribution from a magmatic source deeper in the system.…”

Section: Gold: On Its Original Distribution and Later Metamorphic Remmentioning

confidence: 99%

Mineralogy, geochemistry and sulfur isotope characterization of Cerro de Maimón (Dominican Republic), San Fernando and Antonio (Cuba) lower Cretaceous VMS deposits: Formation during subduction initiation of the proto-Caribbean lithosphere within a fore-arc

Torró

Proenza

Melgarejo

et al. 2016

Ore Geology Reviews

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A chemical model for the concentration of gold in volcanogenic massive sulphide deposits

Cited by 139 publications

References 31 publications

Estudo De Inclusões Fluidas Em Mineralização Sulfetada Vulcanogênica Hidrotermal E De Ouro Orogênico Na Serra Do Ipitinga, Amazônia, Brasil

Estudo De Inclusões Fluidas Em Mineralização Sulfetada Vulcanogênica Hidrotermal E De Ouro Orogênico Na Serra Do Ipitinga, Amazônia, Brasil

Gold Behavior in Supergene Profiles Under Changing Redox Conditions: The Example of the Las Cruces Deposit, Iberian Pyrite Belt

Mineralogy, geochemistry and sulfur isotope characterization of Cerro de Maimón (Dominican Republic), San Fernando and Antonio (Cuba) lower Cretaceous VMS deposits: Formation during subduction initiation of the proto-Caribbean lithosphere within a fore-arc

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