Arc-continent collision and the formation of continental crust: a new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland

Amy E Draut (Corresponding Author), Peter D Clift, Jeffrey M Amato, Jerry Blusztajn, Hans Schouten

Research output: Contribution to journalArticle

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Abstract

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 that 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.
Original languageEnglish
Pages (from-to)485–500
Number of pages16
JournalJournal of the Geological Society
Volume166
Issue number3
DOIs
Publication statusPublished - May 2009

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arc-continent collision
continental crust
Ordovician
collision
magmatism
terrane
rare earth element
melt
Dalradian
tonalite
plate tectonics
orogeny
island arc
continental margin
volcanism
zircon
subduction
thrust
fractionation
crystal

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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 (Corresponding Author); Clift, Peter D; Amato, Jeffrey M; Blusztajn, Jerry; Schouten, Hans.

In: Journal of the Geological Society , Vol. 166, No. 3, 05.2009, p. 485–500.

Research output: Contribution to journalArticle

Draut, Amy E ; Clift, Peter D ; Amato, Jeffrey M ; Blusztajn, Jerry ; Schouten, Hans. / Arc-continent collision and the formation of continental crust : a new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland. In: Journal of the Geological Society . 2009 ; Vol. 166, No. 3. pp. 485–500.
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