Caledonide volcanism in Britain and Ireland

Stillman, C. J.; Francis, E. H.

doi:10.1144/gsl.sp.1979.008.01.67

Cited by 16 publications

(14 citation statements)

References 56 publications

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“…The development of the Ordovician basin of Wales was broadly contemporaneous with subaerial and submarine transitional tholeiitic and calc-alkaline arc volcanism in the Lake District-Leinster Zone, which presently lies to the NW, beyond the Precambrian of the Anglesey (Irish Sea) Horst (Stillman & Francis 1979). Most plate tectonic models (e.g.…”

Section: Basement and General Tectonic Settingmentioning

confidence: 99%

The Ordovician marginal basin of Wales

Kokelaar¹,

Howells²,

Bevins³

et al. 1984

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The Lower Palaeozoic Welsh Basin was founded on immature continental crust. During late Precambrian-early Cambrian times, volcanism and sedimentation were influenced by NE-SW-trending faults which defined the NW and SE margins of the basin. During the Cambrian, marine sediments infilled a graben and at the end of the Tremadoc widespread tectonism was associated with an island-arc volcanic episode. In the Ordovician this subduction-related activity was succeeded by mainly tholeiitic volcanism related to back-arc extension, with the locus of arc volcanism sited further N, in the Lake District--Leinster Zone of the Caledonides. In Wales, the Ordovician volcanic activity shifted in time and space. In S Wales volcanism persisted from the middle Arenig through the Llanvirn. In N Wales the volcanism can be broadly divided into dominantly pre-Caradoc activity in southern Snowdonia and an intra-Caradoc episode in central and northern Snowdonia. In eastern Wales, including the Welsh Borderland, and in Ll~,n, both episodes are represented. In all areas faults greatly influenced both volcanism and sedimentation. Intrusive activity was dominated by high-level emplacement of sills. Granite (s.l.) stocks are restricted to central and northern Snowdonia and Ll~n and many were coeval with extrusive volcanism.Volcanism in the basin was essentially bimodal with voluminous eruptions of tholeiitic basalts with ocean-floor affinities, and of rhyolites. Minor volumes of andesite to rhyodacite resulted from low-pressure fractional crystallization of the tholeiitic basalts. Available evidence suggests that the rhyolites resulted mainly from crustal fusion, although in some instances evolution by crystal fractionation from intermediate magma has been proposed. Calc-alkaline assemblages are petrographically distinct, of minor occurence and, contrary to previous conclusions, are relatively insignificant in the characterization of the tectonic environment of the basin.Throughout the basin, volcanism was generally succeeded by deposition of black muds and then turbidite-dominated sequences.

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Section: Basement and General Tectonic Settingmentioning

confidence: 99%

The Ordovician marginal basin of Wales

Kokelaar¹,

Howells²,

Bevins³

et al. 1984

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“…The significance of these findings is that all the Lower Palaeozoic igneous rocks in Ireland are of volcanic arc/plate margin character. Thus, most of the gabbros described here, if Irish, can only have come from Upper Palaeozoic or Tertiary rock outcrops (Stillman and Francis 1979). This is discussed in more detail below.…”

Section: Sr K R B B a T H T A N B C E P Z R H F S M T I Y Y B S C Cmentioning

confidence: 86%

Striking the Balance: The Roles of Petrography and Geochemistry in Stone Axe Studies in Ireland*

Mandal

1997

Archaeometry

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There has been a long but sporadic history of research on stone axes in Ireland, leading to the formation of the Irish Stone Axe Project (ISAP) in 1990. The purpose of this paper is to outline the research strategy of the project and to indicate the petrological techniques that are being applied in parallel with archaeological and archival studies to classify and identify potential sources for Irish stone axes. These include macroscopic studies, transmitted and reflected light microscopy on polished thin sections and X‐ray fluorescence analyses. The results of the macroscopic examination of 15916 axes indicate that one rock type, porcellanite, was the dominant source, but that a wide range of other lithologies was also exploited. Several avenues for more detailed research are highlighted. A case study of gabbro axes demonstrates the value of this systematic approach to stone axe studies, and the results of this study suggest that some of these axes are petrographically consistent with British Group I, presumed to originate from sources in Cornwall, south‐west England.

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“…It comprises a lower, dominantly volcaniclastic sequence (Slane Group) at least partially Llanvirn in age capped by a suite of mugearite lavas (Mainstre 1952) of calc-alkaline affinities indicating a possible intraplate setting (Stillman & Francis 1978). The geochemistry of these lavas contrasts markedly with that of coeval volcanics in the Bellewstown terrane to the south (see below).…”

Section: The Grangegeeth Terranementioning

confidence: 99%

The Ordovician biogeography of the Grangegeeth terrane and the Iapetus suture zone in eastern Ireland

Owen

Harper

Romano

1992

JGS

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The Caradoc trilobite and brachiopod faunas of the Grangegeeth terrane show marked Scoto-AppalachiadLaurentian affinities. Contrary to some plate tectonic models, this indicates that the terrane must lie to the north of the Iapetus suture. More limited graptolite evidence from the Llanvirn of Grangegeeth suggests that the terrane may have been closer to the Gondwanan margin or at least at higher latitudes earlier in the Ordovician and migrated to low latitudes prior to its eventual accretion onto the Laurentian margin.

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Caledonide volcanism in Britain and Ireland

Cited by 16 publications

References 56 publications

The Ordovician marginal basin of Wales

The Ordovician marginal basin of Wales

Striking the Balance: The Roles of Petrography and Geochemistry in Stone Axe Studies in Ireland*

The Ordovician biogeography of the Grangegeeth terrane and the Iapetus suture zone in eastern Ireland

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