A Fissure‐Controlled Acidic Volcanic Centre (Ordovician) at Yr Arddu, North Wales

Howells, M. F.; Campbell, S. D. G.; Reedman, A. J.; Tunnicliff, S. P.

doi:10.1002/gj.3350220206

Cited by 7 publications

(4 citation statements)

References 14 publications

(15 reference statements)

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“…The controlling influences of major fracture systems on the Arvonian, Tremadoc and Caradoc marginal basin volcanicity is well documented by Kokelaar (1979), Kokelaar et al (1984), Reedman, Leveridge & Evans (1986), Howells, Reedman & Leveridge (1985), Howells, Reedman & Campbell (1986), Howells et al (1987), Campbell et al (1988). These data indicate that the repeated, and often rapid, shallow-level emplacement of large volumes of acid and basic magma was controlled by a framework of deep seated fractures.…”

Section: Influence On Sedimentation and Volcanismmentioning

confidence: 91%

Basement fractures in North Wales: their recognition and control on Caledonian deformation

Wilkinson

Smith

1988

Geol. Mag.

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A detailed survey of the patterns of regional deformation in North Wales has revealed the presence of several discrete, linear zones of anomalous deformation. These zones are distinguished by atypical finite strain values, intense tight to isoclinal folding, non-axial planar cleavages and high metamorphic gradients. A history of prolonged tectonic activity along these zones is indicated by their influence on sedimentation and volcanism. It is proposed that these zones reflect the deformation of the Lower Palaeozoic cover above pre-existing basement fractures. These basement fractures form a framework which divides North Wales into a series of blocks and sub-blocks. The end-Caledonian deformation is explained by a transpression model dominated by SE-directed shear with minor components of strike-slip localized in these zones. The application of this model to other parts of the Welsh Basin is briefly considered.

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Section: Influence On Sedimentation and Volcanismmentioning

confidence: 91%

Basement fractures in North Wales: their recognition and control on Caledonian deformation

Wilkinson

Smith

1988

Geol. Mag.

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“…3C). However, detailed interpretation of these centres (Howells, Reedman & Campbell, 1986;Howells et al 1987;Reedman et al 1985) has indicated the influence of these fractures on the earliest phases of SVG eruption, later rhyolite dome emplacement and late-stage volcanogenic mineralization.…”

Section: A Tectonic Controls Of Magmatismmentioning

confidence: 99%

A Caradoc Failed-Rift within the Ordovician Marginal Basin of Wales

et al. 1988

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The dolerite and basalt intrusions within the Lower Palaeozoic sequence of northwest Wales are largely restricted to the outcrop of Ordovician strata. Their distribution and close association with known volcano-tectonic structures were controlled by a tectonic framework of deep-seated fractures. In central and northern Snowdonia, volcanism during Caradoc times was related to the evolution of a fracture-controlled trough. An increase in the extensional stress across the trough with time is reflected in the progressive increase in basaltic magma movement during the volcanic cycle. The trough represents an attempted rift in the lithospheric plate, which failed to create an ocean basin and was subsequently aborted.

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“…7). The Al rhyolites (phase 1) lie along the NE-SW Yr Arddu Fracture (Howells et al 1987) on the southeast side of the LRTF caldera (Fig. 7 a).…”

Section: B Structural Controls Of Emplacementmentioning

confidence: 99%

“…7 a). This fracture affected sedimentation prior to emplacement of the LRTF, and controlled the eruption of the Yr Arddu Tuffs (Howells et al 1987). The A2 rhyolites (phase 2) are restricted to the southwestern margin of the LRTF caldera (Fig.…”

Section: B Structural Controls Of Emplacementmentioning

confidence: 99%

The emplacement of geochemically distinct groups of rhyolites during the evolution of the Lower Rhyolitic Tuff Formation caldera (Ordovician), North Wales, U.K.

et al. 1987

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Rhyolites in the vicinity of Snowdon (North Wales) are intimately associated with the evolution of the Lower Rhyolitic Tuff Formation (LRTF) caldera of Ordovician (Caradoc) age. They occur as deep-seated dykes, sills and small stocks, shallow-level intrusive domes, and domes extruded within a predominantly shallow-marine environment. Extrusion occurred during three main phases, indicating the episodic availability of rhyolite magma. The rhyolites can be divided on their trace element ratios (e.g. Nb/Zr) into five main groups. Extrusive representatives indicate that each group correlates strongly with a single phase of rhyolite extrusion. Within each group, the distribution and variation of intrusive form with stratigraphic level suggests that geochemically similar rocks were emplaced at approximately the same time. Consequently, the groups represent discrete magma compositions tapped from the evolving Snowdon subvolcanic magma system. Differences in distribution of the groups reflect changes in structural controls of emplacement before and after development of the LRTF caldera.

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A Fissure‐Controlled Acidic Volcanic Centre (Ordovician) at Yr Arddu, North Wales

Cited by 7 publications

References 14 publications

Basement fractures in North Wales: their recognition and control on Caledonian deformation

Basement fractures in North Wales: their recognition and control on Caledonian deformation

A Caradoc Failed-Rift within the Ordovician Marginal Basin of Wales

The emplacement of geochemically distinct groups of rhyolites during the evolution of the Lower Rhyolitic Tuff Formation caldera (Ordovician), North Wales, U.K.

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