A Lower Devonian age for the Corvock Granite and its significance for the structural history of South Mayo and the Laurentian margin of western Ireland

John R. Graham, Nancy R. Riggs

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The Silurian Croagh Patrick succession, which crops out just south of a fundamental Caledonian structural zone near Clew Bay, western Ireland, is a series of psammites and pelites with a strong penetrative cleavage. These rocks are intruded by the Corvock granite. A suite of minor intrusions associated with the granite contains the regional cleavage whereas the Corvock granite is undeformed. New U–Pb dates are 413 +7 / –4 Ma for a strongly cleaved sill and 410 6 4 Ma for the main granite, and closely constrain the age of crystallization of the granite and coeval cleavage formation as Lower Devonian (Lochkovian or Pragian), implying syn-to late-kinematic granite emplacement. These data are consistent with evidence for strong sinistral shear shown by the Ox Mountains granodiorite just to the northeast dated at 412.3 6 0.8 Ma. This Devonian cleavage is superimposed on Ordovician rocks of the South Mayo Trough. The localisation of the strong deformation is interpreted as being due to its position at a restraining bend during regional sinistral motion on a segment of the Fair Head – Clew Bay Line to the north. Contemporaneous deformation in the syn-kinematic Donegal batholith suggests a transfer of sinistral motion to this intra-Grampian structure rather than simple along-strike linkage to the Highland Boundary Fault in Scotland. Our new data indicate diachronous deformation during the late Silurian and early Devonian history of the Irish and Scottish Caledonides and also support previous interpretations of diachronous deformation between these areas and the Appalachian orogens.

Original languageEnglish (US)
Pages (from-to)1-11
Number of pages11
JournalCanadian Journal of Earth Sciences
Volume59
Issue number1
DOIs
StatePublished - 2022

Keywords

  • Caledonides
  • Cleavage formation
  • Devonian
  • Geochronology
  • Granites
  • Ireland

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Fingerprint

Dive into the research topics of 'A Lower Devonian age for the Corvock Granite and its significance for the structural history of South Mayo and the Laurentian margin of western Ireland'. Together they form a unique fingerprint.

Cite this