Detrital U-Pb zircon dating of Lower Ordovician syn-arc-continent collision conglomerates in the Irish Caledonides

Peter D Clift (Corresponding Author), Andrew Carter, Amy E Draut, Long Van Hoang, David M Chew, Hans A Schouten

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Abstract

The Early Ordovician Grampian Orogeny in the British Isles represents a classic example of collision between an oceanic island arc and a passive continental margin, starting around 480 Ma. The South Mayo Trough in western Ireland preserves a complete and well-dated sedimentary record of arc collision. We sampled sandstones and conglomerates from the Rosroe, Maumtrasna and Derryveeny Formations in order to assess erosion rates and patterns during and after arc collision. U–Pb dating of zircons reveals a provenance dominated by erosion from the upper levels of the Dalradian Supergroup (Southern Highland and Argyll Groups), with up to 20% influx from the colliding arc into the Rosroe Formation, but only 6% in the Maumtrasna Formation (~ 465 Ma). The dominant source regions lay to the northeast (e.g. in the vicinity of the Ox Mountains, 50 km distant, along strike). The older portions of the North Mayo Dalradian and its depositional basement (the Annagh Gneiss Complex) do not appear to have been important sources, while the Connemara Dalradian only plays a part after 460 Ma, when it supplies the Derryveeny Formation. By this time all erosion from the arc had effectively ceased and exhumation rates had slowed greatly. The Irish Grampian Orogeny parallels the modern Taiwan collision in showing little role for the colliding arc in the production of sediment. Negligible volumes of arc crust are lost because of erosion during accretion to the continental margin.
Original languageEnglish
Pages (from-to)165–174
Number of pages10
JournalTectonophysics
Volume479
Issue number1-2
Early online date30 Jul 2008
DOIs
Publication statusPublished - 10 Dec 2009

Keywords

  • collision
  • erosion
  • zircon
  • caledonides
  • Grampian

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    Clift, P. D., Carter, A., Draut, A. E., Hoang, L. V., Chew, D. M., & Schouten, H. A. (2009). Detrital U-Pb zircon dating of Lower Ordovician syn-arc-continent collision conglomerates in the Irish Caledonides. Tectonophysics, 479(1-2), 165–174. https://doi.org/10.1016/j.tecto.2008.07.018