A sulphur isotope study on selected Caledonian granites of Britain and Ireland

Laouar, Rabah; Boyce, Adrian J.; Fallick, Anthony E.; Leake, Bernard Elgey

doi:10.1002/gj.3350250318

Cited by 23 publications

(20 citation statements)

References 18 publications

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“…8; Table 2). Consistent with this, Laouar (1987) noted that no sulphide mineralization is observed in granites hosted within Grampian Group units, suggesting that the host rocks of the mineralization may not have been good sulphur sources. There are no published d 34 S sulphide or d…”

Section: Sedimentary S-sourcessupporting

confidence: 60%

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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Section: Sedimentary S-sourcessupporting

confidence: 60%

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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“…Sulphur at Mace Head is close enough to 0%0 to be regarded as magmatic in origin also (Laouar et al 1990, Kennan et al 1988) and the uniformity in values there reinforces this interpretation. The difference between the values for each locality could be explained by differences in 634S of the source granites (cf.…”

Section: Stable Isotopessupporting

confidence: 56%

“…The difference between the values for each locality could be explained by differences in 634S of the source granites (cf. Laouar et al 1990) Fig. 5.…”

Section: Stable Isotopesmentioning

confidence: 99%

Geological, fluid inclusion and stable isotope studies of Mo mineralization, Galway Granite, Ireland

et al. 1992

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Mo mineralization within the Galway Granite at Mace Head and Murvey, Connemara, western Ireland, has many features of classic porphyry Mo deposits including a chemically evolved I-type granite host, associated K-and Si-rich alteration, quartz vein-(Mace Head) and granite-hosted (Murvey) molybdenite, chalcopyrite, pyrite and magnetite mineralization and a gangue assemblage which includes quartz, muscovite and K-feldspar. Most fluid inclusions in quartz veins homogenize in the range 100 350~ and have a salinity of 1 13 eq. wt.% NaC1. They display Th-salinity covariation consistent with a hypothesis of dilution of magmatic water by influx of meteoric water. CO2-bearing inclusions in an intensely mineralized vein at Mace Head provide an estimated minimum trapping temperature and pressure for the mineralizing fluid of 355 ~ and 1.2 kb and are interpreted to represent a H z O -C O 2 fluid, weakly enriched in Mo, produced in a magma chamber by decompression-activated unmixing from a dense Mo-bearing NaC1-H20-CO z fluid. 6348 values of most sulphides range from c. 0%0 at Murvey to 3 4%0 at Mace Head and are consistent with a magmatic origin. Most quartz vein samples have 6180 of 9-10.3%o and were precipitated from a hydrothermal fluid with 6180 of 4.6-6.7%o. Some have 6180 of 6-7%o and reflect introduction of meteoric water along vein margins. Quartz-muscovite oxygen isotope geothermometry combined with fluid inclusion data indicate precipitation of mineralized veins in the temperature range 360-450 ~ and between 1 and 2 kb. Whole rock granite samples display a clear 6180-6D trend towards the composition of Connemara meteoric waters. The mineralization is interpreted as having been produced by highlyfractionated granite magma; meteoric water interaction postdates the main mineralizing event. The differences between the Mace Head and Murvey mineralizations reflect trapping of migrating mineralizing fluid in structural traps at Mace Head and precipitation of mineralization in the granite itself at Murvey.

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“…1). These intrusions reflect, in part, the evolution of the northern part of eastern Avalonia [34][35][36][37][38][39][40][41][42][43][44][45] (and references therein) and the geochronology to be presented here can yield important information on the timing of tectonism during the Acadian phase of the C-AO in the northern England region. The results are further discussed in the context of granite-related molybdenite systems present in the western Ireland (Connemara) sector and in regard to the timing and duration of magmatism and also the tectonic setting of the C-AO.…”

Section: Introductionmentioning

confidence: 99%

Geochronology (Re–Os and U–Pb) and fluid inclusion studies of molybdenite mineralisation associated with the Shap, Skiddaw and Weardale granites, UK

Selby¹,

Conliffe²,

Crowley³

et al. 2008

Applied Earth Science

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Late Devonian magmatism in Northern England records key events associated with the Acadian phase of the Caledonian-Appalachian Orogen (C-AO). Zircon U-Pb and molybdenite Re-Os geochronology date emplacement and mineralisation in the Shap (405?2¡1?8 Ma), Skiddaw (398?8¡0?4 and 392?3¡2?8 Ma) and Weardale granites (398?3¡1?6 Ma). For the Shap granite, mineralisation and magmatism are contemporaneous, with mineralisation being directly associated with the boiling of CO 2 -rich magmatic fluids between 300 and 450uC, and 440 and 620 bars. For the Skiddaw granite, the Re-Os age suggests that sulphide mineralisation occurred post-magmatism (398?8¡0?4 Ma) and was associated with the boiling (275 and 400uC and at 375-475 bars) of a non-magmatic fluid, enriched in N 2 , CH 4 and S, which is isotopically heavy. In contrast, the co-magmatic molybdenite mineralisation of the Weardale granite formed from nonfluid boiling at 476 to 577uC at 1-1?7 kbars. The new accurate and precise ages indicate that magmatism and Mo-mineralisation occurred during the same period across eastern Avalonia (cf. Ireland). In addition, the ages provide a timing of tectonism of the Acadian phase of the C-AO in northern England. Based on the post-tectonic metamorphic mineral growth associated with the Shap and Skiddaw granite aureoles, Acadian deformation in the northern England continued episodically (before ,405 Ma) throughout the Emsian (,398 Ma).

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A sulphur isotope study on selected Caledonian granites of Britain and Ireland

Cited by 23 publications

References 18 publications

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

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

Geological, fluid inclusion and stable isotope studies of Mo mineralization, Galway Granite, Ireland

Geochronology (Re–Os and U–Pb) and fluid inclusion studies of molybdenite mineralisation associated with the Shap, Skiddaw and Weardale granites, UK

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