Rapid tectonic exhumation, detachment faulting and orogenic collapse in the Caledonides of Western Ireland

Peter Dominic Clift, J. F. Dewey, A. E. Draut, D. Chew, M. Mange, P. D. Ryan

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Collision of the oceanic Lough Nafooey Island Arc with the passive margin of Laurentia after 480 Ma in western Ireland resulted in the deformation, magmatism and metamorphism of the Grampian Orogeny, analogous to the modem Taiwan and Miocene New Guinea Orogens. After similar to 470 Ma, the metamorphosed Laurentian margin sediments (Dalradian Supergroup) now exposed in Connemara and North Mayo were cooled rapidly (> 35degreesC/m.y.) and exhumed to the surface. We propose that this exhumation occurred mainly as a result of an oceanward collapse of the colliding arc southwards, probably aided by subduction rollback, into the new trench formed after subduction polarity reversal following collision. The Achill Beg Fault, in particular, along the southern edge of the North Mayo Dalradian Terrane, separates very low-grade sedimentary rocks of the South Mayo Trough (Lough Nafooey forearc) and accreted sedimentary rocks of the Clew Bay Complex from high-grade Dalradian meta-sedimentary rocks, suggesting that this was a major detachment structure. In northern Connemara, the unconformity between the Dalradian and the Silurian cover probably represents an eroded major detachment surface, with the Renvyle-Bofin Slide as a related but subordinate structure. Blocks of sheared mafic and ultramafic rocks in the Dalradian immediately below this unconformity surface probably represent arc lower crustal and mantle rocks or fragments of a high level ophiolite sheet entrained along the detachment during exhumation.

Orogenic collapse was accompanied in the South Mayo Trough by coarse clastic sedimentation derived mostly from the exhuming Dalradian to the north and, to a lesser extent, from the Lough Nafooey Arc to the south. Sediment flow in the South Mayo Trough was dominantly axial, deepening toward the west. Volcanism associated with orogenic collapse (Rosroe and Mweelrea Formations) is variably enriched in high field strength elements, suggesting a heterogeneous enriched mantle wedge under the new post-collisional continental arc. (C) 2004 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)91-113
Number of pages22
JournalTectonophysics
Volume384
Issue number1-4
DOIs
Publication statusPublished - 2004

Keywords

  • caledonides
  • exhumation
  • detachment
  • Ireland
  • ARC-CONTINENT COLLISION
  • DELANEY DOME FORMATION
  • IRISH CALEDONIDES
  • SOUTH-MAYO
  • GEOCHEMICAL EVOLUTION
  • EXTENSIONAL COLLAPSE
  • GRAMPIAN OROGENY
  • DALRADIAN ROCKS
  • EASTERN TAIWAN
  • OKINAWA TROUGH

Cite this

Rapid tectonic exhumation, detachment faulting and orogenic collapse in the Caledonides of Western Ireland. / Clift, Peter Dominic; Dewey, J. F.; Draut, A. E.; Chew, D.; Mange, M.; Ryan, P. D.

In: Tectonophysics, Vol. 384, No. 1-4, 2004, p. 91-113.

Research output: Contribution to journalArticle

Clift, Peter Dominic ; Dewey, J. F. ; Draut, A. E. ; Chew, D. ; Mange, M. ; Ryan, P. D. / Rapid tectonic exhumation, detachment faulting and orogenic collapse in the Caledonides of Western Ireland. In: Tectonophysics. 2004 ; Vol. 384, No. 1-4. pp. 91-113.
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AB - Collision of the oceanic Lough Nafooey Island Arc with the passive margin of Laurentia after 480 Ma in western Ireland resulted in the deformation, magmatism and metamorphism of the Grampian Orogeny, analogous to the modem Taiwan and Miocene New Guinea Orogens. After similar to 470 Ma, the metamorphosed Laurentian margin sediments (Dalradian Supergroup) now exposed in Connemara and North Mayo were cooled rapidly (> 35degreesC/m.y.) and exhumed to the surface. We propose that this exhumation occurred mainly as a result of an oceanward collapse of the colliding arc southwards, probably aided by subduction rollback, into the new trench formed after subduction polarity reversal following collision. The Achill Beg Fault, in particular, along the southern edge of the North Mayo Dalradian Terrane, separates very low-grade sedimentary rocks of the South Mayo Trough (Lough Nafooey forearc) and accreted sedimentary rocks of the Clew Bay Complex from high-grade Dalradian meta-sedimentary rocks, suggesting that this was a major detachment structure. In northern Connemara, the unconformity between the Dalradian and the Silurian cover probably represents an eroded major detachment surface, with the Renvyle-Bofin Slide as a related but subordinate structure. Blocks of sheared mafic and ultramafic rocks in the Dalradian immediately below this unconformity surface probably represent arc lower crustal and mantle rocks or fragments of a high level ophiolite sheet entrained along the detachment during exhumation.Orogenic collapse was accompanied in the South Mayo Trough by coarse clastic sedimentation derived mostly from the exhuming Dalradian to the north and, to a lesser extent, from the Lough Nafooey Arc to the south. Sediment flow in the South Mayo Trough was dominantly axial, deepening toward the west. Volcanism associated with orogenic collapse (Rosroe and Mweelrea Formations) is variably enriched in high field strength elements, suggesting a heterogeneous enriched mantle wedge under the new post-collisional continental arc. (C) 2004 Elsevier B.V. All rights reserved.

KW - caledonides

KW - exhumation

KW - detachment

KW - Ireland

KW - ARC-CONTINENT COLLISION

KW - DELANEY DOME FORMATION

KW - IRISH CALEDONIDES

KW - SOUTH-MAYO

KW - GEOCHEMICAL EVOLUTION

KW - EXTENSIONAL COLLAPSE

KW - GRAMPIAN OROGENY

KW - DALRADIAN ROCKS

KW - EASTERN TAIWAN

KW - OKINAWA TROUGH

U2 - 10.1016/j.tecto.2004.03.009

DO - 10.1016/j.tecto.2004.03.009

M3 - Article

VL - 384

SP - 91

EP - 113

JO - Tectonophysics

JF - Tectonophysics

SN - 0040-1951

IS - 1-4

ER -