A resurgent cauldron in the early Paleozoic of Wales, U.K.

Beavon, Roy V.

doi:10.1016/0377-0273(80)90025-6

Cited by 14 publications

(8 citation statements)

References 27 publications

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“…(3) During the waning stages of caldera magmatism, postcaldera intrusions of various shapes and dimensions intrude at shallow levels, concurrently with emplacement of caldera-filling lavas and minor pyroclastic eruptions (e.g., Galetto et al, 2017;Marsh, 1984;Smith & Bailey, 1968). These include ring dikes, intrusive necks, laccoliths, and other resurgent intrusions that can be associated with extensive hydrothermal alteration and mineral deposits (e.g., Beavon, 1980;Bethke et al, 1997;Fridrich et al, 1991;Kennedy et al, 2012;Lexa et al, 1999;Saunders, 2001;Swanson & McDowell, 1985;Tomek et al, 2017).…”

Section: Citationmentioning

confidence: 99%

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Tomek

Gilmer

Petronis

et al. 2019

Geochem Geophys Geosyst

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Many eroded calderas expose associated postcollapse plutons, but detailed fieldwork‐supported studies have rarely focused on the internal structure that can contribute to understanding of emplacement dynamics. The Alamosa River monzonite pluton is a postcollapse intrusion at the Platoro caldera complex that erupted six large ignimbrites between 30.2 and 28.8 Ma in the Southern Rocky Mountains volcanic field. Magnetic fabrics in this intrusion indicate the pulsed emplacement of a vertically extensive pluton. The magmatic pulses are documented by three concentric domains of magnetic foliations elongated in ~NE‐SW direction, corresponding to structural trends at the Platoro caldera complex and preexisting regional structures. As no evidence for deformation of wall rocks and the adjacent resurgent block has been identified, we interpret the Alamosa River pluton as a postresurgent intrusion. The space‐opening process involved magmatic stoping and small‐scale magma wedging. New SHRIMP‐RG U/Pb zircon dates (28.98 ± 0.18, 27.42 ± 0.35, and 27.32 ± 0.38 Ma) suggest a magmatic lifespan of ~1.7 My for the Alamosa River pluton. Our results indicate that postcaldera magmatism includes pulsed and protracted activity from large intracaldera resurgent plutons to smaller postresurgent stocks and sheeted complexes. As demonstrated by the Alamosa River pluton, some intrusions are emplaced shortly after collapse and resurgence, but postcaldera volcano‐plutonic systems may remain active for several million years or more. We also suggest that subvolcanic magma bodies may be assembled incrementally and that the record of early composite magma lenses preserved as magma wedges are later obliterated by convective flowage and crystallization.

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Section: Citationmentioning

confidence: 99%

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Tomek

Gilmer

Petronis

et al. 2019

Geochem Geophys Geosyst

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“…7 b), and their coincidence in places with NE-SW trending faults, including the Idwal-Hebog Fault, suggests their emplacement was fault-controlled. Their main distribution coincides with the 1-2 km wide apical graben (Beavon, 1980;Reedman et al 1985), bounded on its northwestern side by the NE-SW Beddgelert Fault (Rast, 1961) and on its southeastern side by a series of NE-SW faults, including the Aberglaslyn Fault (Beavon, 1963). 7 b).…”

Section: B Structural Controls Of Emplacementmentioning

confidence: 73%

“…The recognition of three main phases of rhyolite extrusion, and by implication intrusion, during the evolution of the LRTF caldera, rather than a single phase in the waning stages of volcanism as indicated by Rast (1969), Beavon (1980) and , prompts a reconsideration of the geochemically based model of . The emplacement of rhyolite post-URTF cannot be substantiated since sediments post-dating the URTF do not occur in the immediate area of the caldera.…”

Section: Rhyolites Of the Snowdon Volcanic Centrementioning

confidence: 99%

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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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“…In the eastern area a NE-trending fault zone, extending from the vicinity of Moel Ddu through Beddgelert (Fig. 1), was active immediately before, during and after the emplacement of both the lower Pitts Head Tuff and the ash-flow tuffs of the Lower Rhyolitic Tuff Formation (Rast, 1961;Beavon, 1980;Howells, Reedman & Campbell, 1986). Early movement on these faults may have produced a tilt-block topography which restricted the distribution of the lower Pitts Head ash-flow tuff to the western side.…”

Section: A J Reedman and Othersmentioning

confidence: 99%

The Pitts Head Tuff Formation: a subaerial to submarine welded ash-flow tuff of Ordovician age, North Wales

et al. 1987

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The Pitts Head Tuff Formation, of Ordovician (Caradoc) age, was emplaced as a thick (c. 700 m) intracaldera sequence and two outflow units comprising welded acidic ash-flow tuff. The Pitts Head pyroclastic flows were erupted subaerially but the lower and most extensive of the outflows crossed a shoreface, and continued for several kilometres offshore. The flow entered the sea without disruption and, following deflation and tuff emplacement, displaced the shoreface several kilometres to the east and northeast. Post-eruption subsidence in the northeast resulted here in the rapid establishment of environments deeper than had previously existed.The lower outflow tuff is parataxitically to eutaxitically welded in both the subaerial and marine environments. The extremely regular plane-parallel welding foliation of the subaerial tuffs, however, contrasts with the locally highly deformed foliation of the tuff deposited beyond the shoreface. The deformed foliation, associated with irregular zones of intense siliceous nodule development, is ascribed to the upward streaming of water vapour generated at the tuff/sediment boundary. Elsewhere rheomorphism within the tuff was caused by instability resulting from emplacement on slopes related to faulting. Continued movement initiated extensive brecciation, detachment, and local gravity sliding of large rafts of tuff.

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A resurgent cauldron in the early Paleozoic of Wales, U.K.

Cited by 14 publications

References 27 publications

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

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

The Pitts Head Tuff Formation: a subaerial to submarine welded ash-flow tuff of Ordovician age, North Wales

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