The Importance of Oxidized Brines for the Formation of Australian Proterozoic
Stratiform Sediment-Hosted Pb-Zn (Sedex) Deposits

Cooke, David R.; Bull, SW; Large, Ross R.; McGoldrick, Peter

doi:10.2113/gsecongeo.95.1.1

Cited by 273 publications

(182 citation statements)

References 32 publications

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“…We emphasize that highly reduced sulphur content could invoke the reaction of CCD-II fluids with all Fe-bearing minerals (including Fe dolomite and silicates) to produce Fe-poor dolomite, Mg-chlorite and pyrite. The suggested chemical contrast between early (ferroan) and late (non-ferroan) dolomitizing fluids is reminiscent of that advocated for Australian Proterozoic sedex deposits (Cooke et al, 2000) between oxidized (MVT-like) and reduced brines, although the inferred pH characteristics may be quite different. This chemical contrast and the inferred high fluid temperatures give permissive evidence for a somewhat new genetic scenario.…”

Section: Fluid Chemistry and Reaction Drivesmentioning

confidence: 80%

The Ranero Hydrothermal Dolomites (Albian, Karrantza Valley, Northwest Spain): Implications on Conceptual Dolomite Models

Nader

López‐Horgue

Shah

et al. 2012

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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Résumé -Les dolomies hydrothermales de Ranero (Albien, vallée de la Karrantza, nord-ouest de l'Espagne) : conséquences sur les modèles génétiques -Les modalités de gisement, la pétrographie, la géochimie et certaines caractéristiques pétrophysiques des corps dolomitiques associées aux failles dans la zone de Ranero (vallée de la Karrantza, nord-ouest de l'Espagne) sont présentées dans cette étude. Les corps dolomitiques sont encaissés dans des carbonates de plateforme déposés durant l'Albien dans le Bassin Basque-Cantabrique. Les dolomies sont formées au cours d'épisodes hydrothermaux successifs par remplacement ou précipitation -dans les vides laissés par une karstification superficielle et hypogène -et sont étroitement associées à un ensemble de failles et de fractures. La formation des dolomies est précédée et suivie par des dépôts de calcite hydrothermale. L'étude minéralogique et géochimique (XRD, ICP-MS/OES, XRF, isotopes stables et Sr radiogénique) permet de distinguer plusieurs stades de formation. Les dolomies sont ferreuses (au début) ou non-ferreuses (plus tard). Elles sont presque stoechiométriques et présentent une gamme de compositions isotopiques appauvries en δ 18 O (-18,7 à -10,5 ‰ V-PDB) qui témoigne de la multiplicité des stades de dolomitisation et de la température élevée des fluides (150-200 °C). La formation de ces dolomies est précédée et suivie par des stylolithisations conformes à la stratification, ce qui suggère un âge fini-Albien des circulations. La chimie des dolomies, celle des silicates authigènes associés et les relations géométriques de remplacement conduisent à postuler l'action de deux types contrastés de fluides dolomitisants. Chacun d'eux est vraisemblablement dérivé de saumures sulfatées et/ou issues de la compaction, mais ils circulent ensuite dans des environnements lithologiques distincts (silicaté riche en Fe vs carbonaté pauvre en Fe) où la réduction thermique des sulfates les fait évoluer vers des propriétés contrastées : soit vers une composition acide et ferreuse (à même de précipiter une dolomie ferreuse par remplacement de calcaire), soit vers une composition pauvre en Fe et riche en S réduit (réactifs avec la dolomie ferreuse). Les moteurs de ces circulations sont peu contraints par nos observations, mais les deux types de fluides sont visiblement drainés par les failles traversant la bordure de la plateforme et qui sont associées aux diapirs.

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Section: Fluid Chemistry and Reaction Drivesmentioning

confidence: 80%

The Ranero Hydrothermal Dolomites (Albian, Karrantza Valley, Northwest Spain): Implications on Conceptual Dolomite Models

Nader

López‐Horgue

Shah

et al. 2012

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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“…This suggestion has some credence since, along with base metals, gold is known to be concentrated in shale-hosted SEDEX mineralization (e.g. Cooke et al 2000;Alchin & Moore 2005). Furthermore, Willan (1996) demonstrated that the Ben Eagach Schist is regionally enriched by hydrothermal activity in Bi, Sb, As, Mo, Ni and Ba, while in the section between the Tyndrum Fault and the Ericht -Laidon Fault to the NW containing the study area, this unit has elevated Mo, Sb and Bi and isolated occurrences of strongly anomalous Cu, Zn and Pb.…”

Section: Metal Source Rocksmentioning

confidence: 96%

How the Neoproterozoic S-isotope record illuminates the genesis of vein gold systems: an example from the Dalradian Supergroup in Scotland

Hill

Jenkin

Boyce

et al. 2013

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The genesis of quartz vein-hosted gold mineralization in the Neoproterozoic-early Palaeozoic Dalradian Supergroup of Scotland remains controversial. An extensive new dataset of S-isotope analyses from the Tyndrum area, together with correlation of the global Neoproterozoic sedimentary S-isotope dataset to the Dalradian stratigraphy, demonstrates a mixed sedimentary and magmatic sulphur source for the mineralization. d34 S values for early molybdenite-and later gold-bearing mineralization range from 22 to +12‰, but show distinct populations related to mineralization type. Modelling of the relative input of magmatic and sedimentary sulphur into gold-bearing quartz veins with d 34 S values of +12‰ indicates a maximum of 68% magmatic sulphur, and that S-rich, SEDEX-bearing, Easdale Subgroup metasedimentary rocks lying stratigraphically above the host rocks represent the only viable source of sedimentary sulphur in the Dalradian Supergroup. Consequently, the immediate host rocks were not a major source of sulphur to the mineralization, consistent with their low bulk sulphur and lack of metal enrichment. Recent structural models of the Tyndrum area suggest that Easdale Subgroup metasedimentary rocks, enriched in 34 S, sulphur and metals, are repeated at depth owing to folding, and it is suggested that these are the most likely source of sedimentary sulphur, and possibly metals, for the ore fluids.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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“…The saline fluids became hot (T > 150 • C), acidic and oxidizing enough to transport zinc and the ore-related elements from the source (possibly Serra do Garrote carbonaceous phyllite) to the deposition site in the dolomitic rocks (Figure 10). Cooke et al [39] have shown that fluids with this composition can be derived within the basin and are able to transport the ore-related metals. The hot fluids must have been acidic enough to dissolve the dolomitic host and to favor the replacement at the early ore stages by Fe-bearing carbonate and sphalerite (if reduced S was available; e.g., the Vazante Mine).…”

Section: Exploration Guidelinesmentioning

confidence: 99%

The Proterozoic Vazante Hypogene Zinc Silicate District, Minas Gerais, Brazil: A Review of the Ore System Applied to Mineral Exploration

Olivo¹,

Monteiro

Baia³

et al. 2018

Minerals

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Abstract:The Proterozoic Vazante zinc silicate district in Minas Gerais, Brazil, hosts world-class hypogene willemite deposits in dolomitic rocks interbedded with siliciclastic rocks deposited in subtidal to supratidal environments. Willemite ore bodies are structurally controlled along regional NE-trending structures which are interpreted as being active during the Neoproterozoic Brasiliano orogeny. The hydrothermal alteration is characterized by an early stage of Fe-dolomite, which replaced the host dolomitic rocks, followed by precipitation of minor sphalerite and then hematite and willemite. Elements commonly enriched in the zinc ore include As, Ba, Be, Bi, Cd, Co, Fe, Ge, In, Mo, Ni, Sb, Se, U, V and W. Mineralogical, fluid inclusion and isotopic data indicates that mixing of S-poor metalliferous saline fluids with meteoric water favored the formation of willemite ore. Carbonaceous phyllites from the underlying thick siliciclastic sequence show evidence of early enrichment in zinc (and ore-related metals) and remobilization, respectively, prior to and during the Brasiliano orogenic event. This unit is interpreted as a possible source of ore-related elements. It is proposed that during the Brasiliano orogeny, hot (T > 170 • C) saline fluids (>15 wt % eq. NaCl) leached metals from siliciclastic source rocks and precipitated willemite ore in the overlying dolomitic sequence along structures that favored mixing with oxidizing meteoric water.

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The Importance of Oxidized Brines for the Formation of Australian Proterozoic Stratiform Sediment-Hosted Pb-Zn (Sedex) Deposits

Cited by 273 publications

References 32 publications

The Ranero Hydrothermal Dolomites (Albian, Karrantza Valley, Northwest Spain): Implications on Conceptual Dolomite Models

The Ranero Hydrothermal Dolomites (Albian, Karrantza Valley, Northwest Spain): Implications on Conceptual Dolomite Models

How the Neoproterozoic S-isotope record illuminates the genesis of vein gold systems: an example from the Dalradian Supergroup in Scotland

The Proterozoic Vazante Hypogene Zinc Silicate District, Minas Gerais, Brazil: A Review of the Ore System Applied to Mineral Exploration

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