Initiation of Iapetus subduction under Irish Avalonia

McConnell, Brian; Morris, John H.

doi:10.1017/s0016756897006626

Cited by 10 publications

(4 citation statements)

References 28 publications

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“…There has been wide acceptance that pre-Silurian southern Ireland represents part of Avalonia (e.g. Van der Voo 1983Voo , 1988Livermore et al 1985;Pickering et al 1988;Ford et al 1992;Cocks et al 1997;McConnell & Morris 1997;Keppie et al 2003;Tyrrell et al 2007;Fullea et al 2014;Todd 2015), but others have suggested linkages to different peri-Gondwanan domains. One school of thought contends that southern Ireland, Wales and southern England formed part of a number of terranes that collectively formed Cadomia (e.g.…”

Section: Regional Geology and Review Of Terranes In The British Islesmentioning

confidence: 99%

The provenance of the Devonian Old Red Sandstone of the Dingle Peninsula, SW Ireland; the earliest record of Laurentian and peri-Gondwanan sediment mixing in Ireland

Fairey

Kerrison

Meere

et al. 2018

JGS

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The Lower Old Red Sandstone in southern Ireland is hosted in the Early Devonian Dingle Basin, which lies immediately south of the Iapetus Suture on the Dingle Peninsula, County Kerry. The basin developed as a post-Caledonian pullapart structure prior to Acadian deformation, which in turn was followed by end-Carboniferous Variscan deformation. Detrital zircon U-Th-Pb geochronology is complemented by mica Ar-Ar and apatite U-Pb geochronology to gain a comprehensive understanding of the provenance of the Lower Devonian Lower Old Red Sandstone of the Dingle Basin and assess contributions of major tectonic components (e.g. Laurentia, Ganderia). Sedimentary rocks in the Lower Old Red Sandstone have similar detrital zircon age distributions, which are dominated by c. 1.2 Ga zircons as well as late Neoproterozoic grains. This indicates a dominant contribution of detritus of Laurentian affinity as well as contributions from westerly and southerly derived Ganderian detritus. Caledonian uplift of the area north of the Iapetus Suture would have facilitated a large contribution of (peri-)Laurentian material. The Upper Old Red Sandstone on the Dingle Peninsula has a distinctly different detrital zircon character including few late Neoproterozoic zircons and abundant zircons of c. 1.05 Ga age, indicating sediment derivation only from Laurentia and no recycling from the Lower Old Red Sandstone.

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Section: Regional Geology and Review Of Terranes In The British Islesmentioning

confidence: 99%

The provenance of the Devonian Old Red Sandstone of the Dingle Peninsula, SW Ireland; the earliest record of Laurentian and peri-Gondwanan sediment mixing in Ireland

Fairey

Kerrison

Meere

et al. 2018

JGS

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“…Within this sector of the orogenic belt (Fig. 2) tectonic and magmatic processes involved the accretion of predominantly Ordovician and Silurian turbidite and volcaniclastic sediments (Morris 1987; McConnell & Morris 1997).…”

Section: Geophysical and Geological Backgroundmentioning

confidence: 99%

The fine-scale structure of upper continental lithosphere from seismic waveform methods: insights into Phanerozoic crustal formation processes

O’Reilly

Hauser

Readman

2010

Geophysical Journal International

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S U M M A R YStudies of the fine-scale structure of the continental lithosphere using seismic coda, associated with reflections from within the crust and the uppermost mantle, have almost solely been based on the compressional wavefield, observed at near vertical to wide-angle incidence. Here the results from a full waveform analysis of both P-and S-wave coda, obtained during a crustal scale wide-angle refraction experiment, from southwest Ireland are presented. The basic foundation for the study is a 2-D model for the P-and S-wave structure of the crust and its chemical composition, based on traveltime inversion of first arrivals and reflections for the Irish Caledonides. This sector of the Caledonian orogenic belt straddles the boundary between the Laurentian and Avalonian tectonic plates, along the Iapetus Suture Zone. The excellent quality and relatively broad frequency range (e.g. 1-20 Hz) of the P-and S-wave coda permits finer structure in the upper 40 km of lithosphere to be resolved than would be possible using just primary seismic phases. A series of 1-D waveform calculations are performed to systematically build a model for the fine-scale structure of the 32-km-thick crust and the uppermost mantle lithosphere. Petrophysical and geochemical data from felsic lowercrustal xenoliths from Central Ireland place limits on the permitted velocity fluctuations. Additional constraints are imposed by vertical P-wave reflections observed on contiguous offshore seismic reflection profiles. The results indicate that the uppermost mantle to a depth of ca. 40 km consists of a vertically stacked sequence of alternating high (V p ∼ 8.0 km s −1 ) and low (V p ∼ 7.25 km s −1 ) velocity layers. Each layer is about 500 m thick with a V p /V s ratio ∼1.73. These layers are interpreted as a series of lens-shaped mafic sill complexes, intruded into the subcrustal lithosphere. The fine structure within the lower crust consists of similar seismic velocity fluctuations (V p ∼ 6.4 and 7.1 km s −1 ) but on a scale of 200-300 m thickness. Velocity variations within the lower crust are consistent with the petrophysical properties of metapelitic, orthogneissic and psammitic lithologies, from lower-crustal xenoliths in Central Ireland, and with similar exhumed sections of lower crust in southern Europe. These results support tectonic theories for the origin of the crust by tectonic accretion of predominantly sedimentary and volcaniclastic material derived from oceanic, island-arc and continental margin sources during the Caledonian orogenic cycle. A conceptual model for crustal accretion and growth involves partial melting of the accreted sedimentary wedge, producing granites and a chemically differentiated crust during the late Caledonian (latest Silurian/early Devonian). The heat source that drove melting of the accreted sediments may have been provided by the interpreted mafic sills intruded into the uppermost mantle during oblique late Caledonian (sinistral) collision of the Laurentian and Avalonian plates.

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“…According to currently applied plate tectonic reconstructions (e.g. McKerrow & Cocks 1995), Ordovician to Devonian magmatic activity in south-east Ireland originated in the same tectonic environment as the Lake District and East Anglia, although McConnell & Morris (1997) mention that the exact relationship between south-east Ireland and the Lake District has yet to be clarified. Also in the Brabant Massif there was some magmatic activity during Early Palaeozoic times (e.g.…”

Section: Regional Settingmentioning

confidence: 99%

Boron metasomatism in the Brabant Massif (Belgium): Geochemical and petrographical evidence of Devonian tourmalinite pebbles

Corteel¹,

Paepe²

2003

Netherlands Journal of Geosciences

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G AbstractNew petrographical and geochemical evidence of tourmalinite pebbles from two Lower and three Middle Devonian formations from Belgium is presented. Petrography, REE, transition metal and microprobe data of the studied rocks suggest it are (meta) sediment-derived tourmalinites formed by boron metasomatism (and hydrothermal brecciation) in an intrusive setting. Tourmaline mineralizations within eastern Avalonia are known in south-east Ireland, the English Lake District and East Anglia. Based on previously suggested relations between Early Palaeozoic igneous activity in last two mentioned regions and the Brabant Massif, it is presumed that the Brabant Massif also underwent granite-related tourmalinization and that this was the source of the studied pebbles. Petrologie differences between pebbles found in Middle Devonian formations and pebbles from Lower Devonian formations, suggest that fluid circulation occurred on a regional scale, possibly extending into the Stavelot massif.

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Initiation of Iapetus subduction under Irish Avalonia

Cited by 10 publications

References 28 publications

The provenance of the Devonian Old Red Sandstone of the Dingle Peninsula, SW Ireland; the earliest record of Laurentian and peri-Gondwanan sediment mixing in Ireland

The provenance of the Devonian Old Red Sandstone of the Dingle Peninsula, SW Ireland; the earliest record of Laurentian and peri-Gondwanan sediment mixing in Ireland

The fine-scale structure of upper continental lithosphere from seismic waveform methods: insights into Phanerozoic crustal formation processes

Boron metasomatism in the Brabant Massif (Belgium): Geochemical and petrographical evidence of Devonian tourmalinite pebbles

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