Permo–Triassic unconformity-related Au-Pd mineralisation, South Devon, UK: new insights and the European perspective

Shepherd, T. J.; Bouch, Jon E.; Gunn, Andrew; McKervey, John; Naden, Jonathan; Scrivener, R. C.; Styles, M. T.; Large, D.

doi:10.1007/s00126-004-0459-3

Cited by 34 publications

(13 citation statements)

References 33 publications

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“…However, we favour a model which involves transport and deposition of gold from a basinal brine type fluid, in a similar fashion to red-bed Au-Pd mineralization (e.g. Shepherd et al, 2005) rather than localized remobilization of orogenic gold mineralization as envisaged for Curraghinalt (e.g. Wilkinson et al, 1999).…”

Section: Discussionmentioning

confidence: 92%

“…Evidence for transport of gold by comparable fluids is seen in red-bed Au-Pd mineralization e.g. Coronation Hill, Australia (Mernagh et al, 1994); South Devon, UK (Shepherd et al, 2005); and Bleida Far West, Morocco (Ghorfi et al, 2006). These deposits display remarkably similar features to Bohaun, typically including abundant hematite, sulphide-poor ore mineral assemblages, an association with brittle structures, open-space textures, variable to typically strongly saline fluids, at temperatures of <300°C.…”

Section: Late Stage Brinesmentioning

confidence: 97%

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Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

et al. 2011

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The Bohaun gold deposit in County Galway, western Ireland is located in the Caledonian orogenic belt, proximal to a major accretionary boundary. The mineralization is hosted in a normal extensional fault, representing a zone of repeated extension and vein infilling of open cavities, within clastic sedimentary rocks, which have only reached the late diagenetic zone of low-grade metamorphism.The mineralization consists of undeformed veins, stockworks and breccias. Quartz dominates all the veins and commonly displays multiple growth stages and a variety of classic epithermal textures, including comb, plumose and banded, indicative of low confining pressures. The veins have a simple mineralogy comprising quartz-sericite-chlorite with minor sulfides, hematite, rare visible gold, with a high silver content (up to 41 wt %), and late barite and dolomite.Vein quartz is associated with two fluids compositions: Type I with moderate to high salinity (8.0-23.6 wt % NaCl equiv) and Type II with low to moderate salinity (0.0-7.8 wt % NaCl equiv). CO 2 contents in both fluid types are <3.5 wt percent. The majority of fluid inclusion homogenization temperatures range from 126 to 257 o C and geologically constrained depth estimates (≤5 km) indicate maximum fluid inclusion trapping temperatures between 175 and 245°C.The geodynamic setting of Bohaun, which comprises a deformed continental margin of an allochthonous terrane, is typical of orogenic gold deposits. However, an orogenic association for the Bohaun mineralization is discounted on the basis of fluid inclusion evidence, atypical vein textures, gold grain composition and undeformed veins. While vein textures locally resemble those found in epithermal quartz-adularia mineralization, there is no obvious magmatic association and alteration is restricted to the veins and immediate host rocks. The origin of the gold at Bohaun remains enigmatic. However, we favor an association with widespread Carboniferous or later mineralizing fluids and a model which involves transport and deposition of gold from a basinal brine type fluid, in a similar fashion to red-bed Au-Pd mineralization. Bohaun provides further evidence that low temperature brines may be capable of generating economic grade gold mineralization, independent of other fluids.3

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Section: Discussionmentioning

confidence: 92%

Section: Late Stage Brinesmentioning

confidence: 97%

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

et al. 2011

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“…The data for Triassic samples are particularly pertinent to Au mineralization of the sub‐Permo‐Triassic unconformity in Europe. From the UK to the Czech Republic, Au has precipitated close to the unconformity, interpreted as a redox boundary (Shepherd et al ., ). The data from numerous Triassic sites indicate that the redox concentration of Au and associated elements is widespread and need not require an exceptional source.…”

Section: Discussionmentioning

confidence: 97%

“…To date, such deposits are exceptional and have been linked to anomalous Au availability through volcanic activity (Colman and Cooper, ). However, there is a growing recognition that reduction can cause the solubilization and redistribution of Au and other rare metals at low temperatures (Shepherd et al ., ). This raises the possibility that there may be widespread mobility of Au in sediments with variable redox conditions, in contrast to its purported inert behaviour.…”

Section: Introductionmentioning

confidence: 97%

“…Gold mineralization can occur in or adjacent to continental red beds (red sandstones and mudrocks), implying the mobilization and fixing of Au by low‐temperature processes (Shepherd et al ., ; Spinks et al ., ). To date, such deposits are exceptional and have been linked to anomalous Au availability through volcanic activity (Colman and Cooper, ).…”

Section: Introductionmentioning

confidence: 99%

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Low‐temperature concentration of tellurium and gold in continental red bed successions

2016

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There is very little understanding of tellurium (Te) distribution and behaviour in sedimentary rocks. A suite of 15 samples of reduction spheroids (centimetre-scale pale spheroids in otherwise red rock), including samples from eight localities in Triassic red beds across the British Isles, were mapped for Te using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. Almost all showed enrichment in Te in the cores of the spheroids relative to background red bed concentrations, by up to four orders of magnitude. Some were also enriched over background in gold and/or mercury. In one case, discrete telluride minerals were recorded. The data show that Te is mobile and can be concentrated in low-temperature sedimentary environments, controlled by redox variations. The consistency in enrichment across widely separate localities implies that the enrichment is a normal aspect of red bed diagenesis and so likely to be controlled by a ubiquitous process, such as microbial activity.

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Gold–palladium mineralization at Bleïda Far West, Bou Azzer–El Graara Inlier, Anti-Atlas, Morocco

et al. 2006

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Permo–Triassic unconformity-related Au-Pd mineralisation, South Devon, UK: new insights and the European perspective

Cited by 34 publications

References 33 publications

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

Low‐temperature concentration of tellurium and gold in continental red bed successions

Gold–palladium mineralization at Bleïda Far West, Bou Azzer–El Graara Inlier, Anti-Atlas, Morocco

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