The Geology of the Minor Intrusions of West Cork, Ireland

Coe, K

doi:10.1016/s0016-7878(69)80032-5

Cited by 7 publications

(4 citation statements)

References 5 publications

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“…1). The pipes, dykes and sills are dominated by lamprophyric and trachytic compositions, (Coe, 1966;Pracht, 1994Pracht, , 2000Kinnaird, 1995, 1997;Pracht and Timmerman, 2004;Brady, 2010) and intrude siliciclastic Carboniferous rocks that contain only minor calcareous mudstones (Reenydonagan Formation; Fig. 1a).…”

Section: Field Relations and Rock Texturesmentioning

confidence: 99%

“…Radiometric ages range from 314.44Ô1.00 Ma for a penetratively deformed ultramafic alkaline lamprophyre pipe containing a mantle xenocryst assemblage to 296.88Ô0.06 Ma for an undeformed post-orogenic dyke (Pracht and Timmerman, 2004;Quinn et al, 2005), showing that the majority of the intrusions were emplaced before the end of Variscan deformation. The tuffisitic subvolcanic intrusion at Cahermore was briefly described by Coe (1966) as a fluidized breccia pipe and later described as pyroclastic by Pracht and Kinnaird (1995).…”

Section: Field Relations and Rock Texturesmentioning

confidence: 99%

“…A CARBONIFEROUS tuffisitic intrusion at Cahermore on the southern Beara Peninsula of southwest Ireland is one of a number of subvolcanic intrusions that have been reported to contain significant concentrations of carbonate, leading Coe (1969) to compare them with carbonatites. However, the carbonate-rich intrusions have not previously been fully described or their petrogenesis established due to their lowgrade regional metamorphic history (Pracht, 1994(Pracht, , 2000Pracht and Kinnaird 1997).…”

Section: Introductionmentioning

confidence: 99%

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A mantle-derived dolomite silicocarbonatite from the southwest coast of Ireland

Brady¹,

Moore²

2012

Mineral. mag.

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The magma source and evolution of a zoned breccia pipe on the southern Beara Peninsula in southwest Ireland are investigated using the geochemistry of the host mineral assemblages. The clast-poor inner zone of the pipe has a magnesium-rich silicocarbonatite whole-rock composition (14.30 wt.% MgO; 31.80 wt.% SiO2). The silicocarbonatite has retained an ultimate mantle source 13C isotopic composition after metamorphism, consistent with the presence of mantle debris. The silicocarbonatite is Cr-, Ni- and Co-rich (847 ppm, 611 ppm and 60 ppm, respectively) but REE depleted compared with volcanic dolomite carbonatites worldwide. The mineral assemblage consists of Sr-rich (0.55 wt.% SrO) ferroan dolomite, magnesite and pseudomorphs of chlorite after phlogopite, consistent with derivation from a carbonated and hydrated mantle. However, chrome spinel crystals (≤4 40.14 wt.% Cr2O3) are compositionally indistinguishable from unmetasomatized spinel macrocrysts in kimberlites. The silicocarbonatite is inferred to represent a magma produced by partial melting of metasomatized mantle at physical conditions between those in which primary dolomite carbonatite and ultramafic magmas of high-pressure origin form. The primary silicocarbonatite magma ascended and sampled mantle material in a manner similar to kimberlite, and subsequently lost volatile components due to release of metasomatic fluids and later metamorphism.

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Section: Field Relations and Rock Texturesmentioning

confidence: 99%

Section: Field Relations and Rock Texturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A mantle-derived dolomite silicocarbonatite from the southwest coast of Ireland

Brady¹,

Moore²

2012

Mineral. mag.

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“…Coe (1969) constructed a seven-stage deformation sequence with three intrusive phases and two deformation events, which was based largely on the relationship of the sills and dykes to the country rock. However, substantiation of four stages of intrusions and two stages of deformation, as put forward by Coe (1969) and Coe and Selwood (1968), has been rejected by Cooper et al (1986) and Pracht (1994). Williams et al (1989) envisaged that all the tectonic features developed during a single extended phase of deformation.…”

Section: Relationship Between Magmatism and Deformationmentioning

confidence: 99%

Carboniferous subvolcanic activity on the Beara Peninsula, SW Ireland

Pracht

Kinnaird

1997

Geol. J.

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Magmatic activity associated with the Munster Basin has been more widespread than previously reported. The Munster Basin is a substantial sedimentary basin, and towards the end of its extensional phase of development, at the beginning of the Variscan orogeny in Ireland, numerous intrusions were emplaced into consolidated Upper Devonian and Lower Carboniferous sediments on the Beara Peninsula. One hundred and sixty-four sills and dykes have been mapped which are subalkaline to alkaline in nature. Two separate suites have been identi®ed. The northern suite comprises subalkaline basalts of Cod's Head and Dursey Island which are intruded into Devonian Red Beds, and the southern suite comprises alkali basalts, trachytes and phonolites which crop out along 9 km of the south coast of the Beara Peninsula and are suggested as Brigantian in age. They are intruded into Devonian Red Beds and marine Lower Carboniferous strata and are therefore later than the tholeiitic magmatism on the Iveragh peninsula to the north. The alkaline magmatism on Beara was induced by lithospheric thinning and controlled partly by pre-existing zones of weakness in the Caledonide crust and partly by fracture zones that developed parallel to the Munster Basin margin as it subsided. In contrast to the Iveragh Peninsula, the stretching factor for the Beara lithosphere was never large enough to lead to the production of tholeiitic magmas.

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The Geology of the Western Approaches

Owen

1974

The Ocean Basins and Margins

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The Geology of the Minor Intrusions of West Cork, Ireland

Cited by 7 publications

References 5 publications

A mantle-derived dolomite silicocarbonatite from the southwest coast of Ireland

A mantle-derived dolomite silicocarbonatite from the southwest coast of Ireland

Carboniferous subvolcanic activity on the Beara Peninsula, SW Ireland

The Geology of the Western Approaches

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