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Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny

Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny
Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny
The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U–Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a c. 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a c. 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at c. 475 Ma. Metamorphic cooling ages from the Tyrone Central Inlier imply arc–continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus.
0016-7649
837-850
Cooper, M.R.
64aa3faa-3106-4a54-8cb6-7920c5c09f22
Crowley, Q.G.
9886c7c5-bd3a-4640-bac7-9a7c2de50865
Hollis, S.P.
61c30119-6a19-4985-940b-99fcca8da59e
Noble, S.R.
9f757555-802d-4b9d-9248-b4a30dcf03f4
Roberts, S.
f095c7ab-a37b-4064-8a41-ae4820832856
Chew, D.
0e9202f4-dc32-41a8-90dc-0d7c181c58b4
Earls, G.
202c889a-7f3b-458b-96d2-0d827fed94fc
Herrington, R.
40a3682c-debf-4944-b4c7-6cdfee6c79f5
Merriman, R. J.
59443119-e4a9-49c0-b0d4-2214ee9defb7
Cooper, M.R.
64aa3faa-3106-4a54-8cb6-7920c5c09f22
Crowley, Q.G.
9886c7c5-bd3a-4640-bac7-9a7c2de50865
Hollis, S.P.
61c30119-6a19-4985-940b-99fcca8da59e
Noble, S.R.
9f757555-802d-4b9d-9248-b4a30dcf03f4
Roberts, S.
f095c7ab-a37b-4064-8a41-ae4820832856
Chew, D.
0e9202f4-dc32-41a8-90dc-0d7c181c58b4
Earls, G.
202c889a-7f3b-458b-96d2-0d827fed94fc
Herrington, R.
40a3682c-debf-4944-b4c7-6cdfee6c79f5
Merriman, R. J.
59443119-e4a9-49c0-b0d4-2214ee9defb7

Cooper, M.R., Crowley, Q.G., Hollis, S.P., Noble, S.R., Roberts, S., Chew, D., Earls, G., Herrington, R. and Merriman, R. J. (2011) Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny. Journal of the Geological Society, 168 (4), 837-850. (doi:10.1144/0016-76492010-164).

Record type: Article

Abstract

The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U–Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a c. 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a c. 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at c. 475 Ma. Metamorphic cooling ages from the Tyrone Central Inlier imply arc–continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus.

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Published date: July 2011

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Local EPrints ID: 191579
URI: http://eprints.soton.ac.uk/id/eprint/191579
ISSN: 0016-7649
PURE UUID: 3632511c-1b89-439c-9ae0-cfe475965134
ORCID for S. Roberts: ORCID iD orcid.org/0000-0003-4755-6703

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Date deposited: 22 Jun 2011 10:43
Last modified: 19 Nov 2019 02:02

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Author: M.R. Cooper
Author: Q.G. Crowley
Author: S.P. Hollis
Author: S.R. Noble
Author: S. Roberts ORCID iD
Author: D. Chew
Author: G. Earls
Author: R. Herrington
Author: R. J. Merriman

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