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Basaltic maar-diatreme volcanism in the Lower Carboniferous of the Limerick Basin (SW Ireland)

Basaltic maar-diatreme volcanism in the Lower Carboniferous of the Limerick Basin (SW Ireland)
Basaltic maar-diatreme volcanism in the Lower Carboniferous of the Limerick Basin (SW Ireland)


Lead-zinc exploration drilling within the Limerick Basin (SW Ireland) has revealed the deep internal architecture and extra-crater deposits of five alkali-basaltic maar-diatremes. These were emplaced as part of a regional north-east south-west tectonomagmatic trend during the Lower Carboniferous Period. Field relationships and textural observations suggest that the diatremes erupted into a shallow submarine environment. Limerick trace element data indicates a genetic relationship between the diatremes and extra-crater successions of the Knockroe Formation, which records multiple diatreme filling and emptying cycles. Deposition was controlled largely by bathymetry defined by the surrounding Waulsortian carbonate mounds. An initial non-diatreme forming eruption stage occurred at the water-sediment interface, with magma-water interaction prevented by high magma ascent rates. This was followed by seawater incursion and the onset of phreatomagmatic activity. Magma-water interaction generated poorly vesicular blocky clasts, although the co-occurrence of plastically deformed and highly vesicular clasts indicate that phreatomagmatic and magmatic processes were not mutually exclusive. At a later stage, the diatreme filled with a slurry of juvenile lapilli and country rock lithic clasts, homogenised by the action of debris jets. The resulting extra-crater deposits eventually emerged above sea level, so that water ingress significantly declined, and late-stage magmatic processes became dominant. These deposits, largely confined to the deep vents, incorporate high concentrations of partially sintered globular and large ‘raggy’ lapilli showing evidence for heat retention. Our study provides new insights into the dynamics and evolution of basaltic diatremes erupting into a shallow water (20–120 m) submarine environment.
Maar-diatremes, Phreatomagmatic, Lower Carboniferous, Shallow marine environment
0258-8900
37
Elliott, H.A.L.
8eb2c088-0bbd-4b6c-a991-64894cf79c25
Gernon, T.M.
658041a0-fdd1-4516-85f4-98895a39235e
Roberts, S.
f095c7ab-a37b-4064-8a41-ae4820832856
Hewson, C.
48e93ffd-9f62-491b-b3cb-2306f88e6391
Elliott, H.A.L.
8eb2c088-0bbd-4b6c-a991-64894cf79c25
Gernon, T.M.
658041a0-fdd1-4516-85f4-98895a39235e
Roberts, S.
f095c7ab-a37b-4064-8a41-ae4820832856
Hewson, C.
48e93ffd-9f62-491b-b3cb-2306f88e6391

Elliott, H.A.L., Gernon, T.M., Roberts, S. and Hewson, C. (2015) Basaltic maar-diatreme volcanism in the Lower Carboniferous of the Limerick Basin (SW Ireland). Bulletin of Volcanology, 77 (5), 37. (doi:10.1007/s00445-015-0922-2).

Record type: Article

Abstract



Lead-zinc exploration drilling within the Limerick Basin (SW Ireland) has revealed the deep internal architecture and extra-crater deposits of five alkali-basaltic maar-diatremes. These were emplaced as part of a regional north-east south-west tectonomagmatic trend during the Lower Carboniferous Period. Field relationships and textural observations suggest that the diatremes erupted into a shallow submarine environment. Limerick trace element data indicates a genetic relationship between the diatremes and extra-crater successions of the Knockroe Formation, which records multiple diatreme filling and emptying cycles. Deposition was controlled largely by bathymetry defined by the surrounding Waulsortian carbonate mounds. An initial non-diatreme forming eruption stage occurred at the water-sediment interface, with magma-water interaction prevented by high magma ascent rates. This was followed by seawater incursion and the onset of phreatomagmatic activity. Magma-water interaction generated poorly vesicular blocky clasts, although the co-occurrence of plastically deformed and highly vesicular clasts indicate that phreatomagmatic and magmatic processes were not mutually exclusive. At a later stage, the diatreme filled with a slurry of juvenile lapilli and country rock lithic clasts, homogenised by the action of debris jets. The resulting extra-crater deposits eventually emerged above sea level, so that water ingress significantly declined, and late-stage magmatic processes became dominant. These deposits, largely confined to the deep vents, incorporate high concentrations of partially sintered globular and large ‘raggy’ lapilli showing evidence for heat retention. Our study provides new insights into the dynamics and evolution of basaltic diatremes erupting into a shallow water (20–120 m) submarine environment.

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More information

Published date: April 2015
Keywords: Maar-diatremes, Phreatomagmatic, Lower Carboniferous, Shallow marine environment
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 377708
URI: http://eprints.soton.ac.uk/id/eprint/377708
ISSN: 0258-8900
PURE UUID: 049e9d3a-eab2-449e-a00a-b1eb0517a56b
ORCID for T.M. Gernon: ORCID iD orcid.org/0000-0002-7717-2092
ORCID for S. Roberts: ORCID iD orcid.org/0000-0003-4755-6703

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Date deposited: 03 Jun 2015 10:32
Last modified: 15 Mar 2024 03:36

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Contributors

Author: H.A.L. Elliott
Author: T.M. Gernon ORCID iD
Author: S. Roberts ORCID iD
Author: C. Hewson

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