Arc–continent collision and the formation of continental crust : a new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland
Draut, Amy E.
Clift, Peter D.
Amato, Jeffrey M.
Blusztajn, Jerzy S.
Schouten, Hans A.
MetadataShow full item record
Collisions between oceanic island-arc terranes and passive continental margins are thought to have been important in the formation of continental crust throughout much of Earth’s history. Magmatic evolution during this stage of the plate-tectonic cycle is evident in several areas of the Ordovician Grampian-Taconic Orogen, as we demonstrate in the first detailed geochemical study of the Tyrone Igneous Complex, Ireland. New U–Pb zircon dating yields ages of 493 ± 2 Ma from a primitive mafic intrusion, indicating intra-oceanic subduction in Tremadoc time, and 475 ± 10 Ma from a light-rare-earth-element (LREE)-enriched tonalite intrusion that incorporated Laurentian continental material by early Arenig time (Early Ordovician, Stage 2) during arc-continent collision. Notably, LREE enrichment in volcanism and silicic intrusions of the Tyrone Igneous Complex exceeds that of average Dalradian (Laurentian) continental material which would have been thrust under the colliding forearc and potentially recycled into arc magmatism. This implies that crystal fractionation, in addition to magmatic mixing and assimilation, was important to the formation of new crust in the Grampian-Taconic Orogeny. Because similar super-enrichment of orogenic melts occurred elsewhere in the Caledonides in the British Isles and Newfoundland, the addition of new, highly enriched melt to this accreted arc terrane was apparently widespread spatially and temporally. Such super-enrichment of magmatism, especially if accompanied by loss of corresponding lower crustal residues, supports the theory that arc-continent collision plays an important role in altering bulk crustal composition toward typical values for ancient continental crust.
Author Posting. © Geological Society of London, 2009. This is the author's version of the work. It is posted here by permission of Geological Society of London for personal use, not for redistribution. The definitive version was published in Journal of the Geological Society 166 (2009): 485-500, doi:10.1144/0016-76492008-102.
Suggested CitationPreprint: Draut, Amy E., Clift, Peter D., Amato, Jeffrey M., Blusztajn, Jerzy S., Schouten, Hans A., "Arc–continent collision and the formation of continental crust : a new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland", 2008-06-23, https://doi.org/10.1144/0016-76492008-102, https://hdl.handle.net/1912/2831
Showing items related by title, author, creator and subject.
Clift, Peter D.; Schouten, Hans A.; Vannucchi, Paola (2008-02-13)Subduction zones are both the source of most new continental crust and the locations where crustal material is returned to the upper mantle. Globally the total amount of continental crust and sediment subducted below ...
Draut, Amy E.; Clift, Peter D. (Geological Society of London, 2002)Dalradian meta-sediments of the Laurentian margin and mafic intrusions thereof in SW Connemara, Ireland, tectonically overlie meta-rhyolites of the Delaney Dome Formation. The two units are separated by the Mannin Thrust. ...
Detrital U–Pb zircon dating of lower Ordovician syn-arc-continent collision conglomerates in the Irish Caledonides Clift, Peter D.; Carter, Andrew; Draut, Amy E.; Long, Hoang Van; Chew, David M.; Schouten, Hans A. (2008-04-15)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 ...