A U-Pb age for the late caledonian Sperrin Mountains minor intrusions suite in the north of Ireland: Timing of slab break-off in the Grampian terrane and the significance of deep-seated, crustal lineaments

M. R. Cooper, Q. G. Crowley, S. P. Hollis, S. R. Noble, P. J. Henney

Research output: Contribution to journalArticlepeer-review

Abstract

An intrusion of trachy-andesite, representative of a newly discovered suite of high-K-Ba-Sr, calc-alkaline minor intrusions (termed herein the Sperrin Mountains suite), hosted within the Grampian terrane in the north of Ireland, has been dated by U-Pb zircon at 426.69 ± 0.85 Ma (mid-Silurian; wenlock-Ludlow boundary). Geochemistry reveals a close association with the Fanad, Ardara and Thorr plutons of the Donegal Batholith and the Argyll and Northern Highlands Suite of Scotland. The deep-seated Omagh Lineament appears to have limited eastward propagation of the Sperrin Mountains suite from beneath the main centre of granitic magmatism in Donegal. A Hf depleted mantle model age (TDMHf) of c. 800 Ma for trachy-andesite zircons indicates partial melting from a source previously separated from the mantle. whole-rock geochemistry of the suite is consistent with a model of partial melting, triggered by slab break-off, following thrusting of Ganderia-Avalonia under the Southern Uplands-Down-Longford accretionary prism (i.e. Laurentian margin). The new age constrains the timing of this event in the north of Ireland and is consistent with the petrogenesis of Late Caledonian high-K granites, appinites and minor intrusions across the Caledonides of northern Britain and Ireland.

Original languageEnglish
Pages (from-to)603-614
Number of pages12
JournalJournal of the Geological Society
Volume170
Issue number5
DOIs
Publication statusPublished - 1 Sep 2013

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