Laurentian crustal recycling in the Ordovician Grampian Orogeny : Nd isotopic evidence from western Ireland

View/ Open
Date
2004-04-21Author
Draut, Amy E.
Concept link
Clift, Peter D.
Concept link
Chew, David M.
Concept link
Cooper, Matthew J.
Concept link
Taylor, Rex N.
Concept link
Hannigan, Robyn E.
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/211As published
https://doi.org/10.1017/S001675680400891XDOI
10.1017/S001675680400891XAbstract
Because magmatism associated with subduction is thought to be the principal source for continental crust generation, assessing the relative contribution of pre-existing (subducted and assimilated) continental material to arc magmatism in accreted arcs is important to understanding the origin of continental crust. We present a detailed Nd isotopic stratigraphy for volcanic and volcaniclastic formations from the South Mayo Trough, an accreted oceanic arc exposed in the western Irish Caledonides. These units span an arc–continent collision event, the Grampian (Taconic) Orogeny, in which an intra-oceanic island arc was accreted onto the passive continental margin of Laurentia starting at [similar] 475 Ma (Arenig). The stratigraphy corresponding to pre-, syn- and post-collisional volcanism reveals a progression of [varepsilon]Nd(t) from strongly positive values, consistent with melt derivation almost exclusively from oceanic mantle beneath the arc, to strongly negative values, indicating incorporation of continental material into the melt. Using [varepsilon]Nd(t) values of meta-sediments that represent the Laurentian passive margin and accretionary prism, we are able to quantify the relative proportions of continent-derived melt at various stages of arc formation and accretion. Mass balance calculations show that mantle-derived magmatism contributes substantially to melt production during all stages of arc–continent collision, never accounting for less than 21% of the total. This implies that a significant addition of new, rather than recycled, continental crust can accompany arc–continent collision and continental arc magmatism.
Description
Author Posting. © Cambridge University Press, 2004. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Geological Magazine 141 (2004): 195-207, doi:10.1017/S001675680400891X.
Collections
Suggested Citation
Geological Magazine 141 (2004): 195-207Related items
Showing items related by title, author, creator and subject.
-
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. (2008-06-23)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 ... -
Western South Atlantic holocene and glacial deepwater hydrography derived from benthic foraminiferal Cd/Ca and stable carbon isotope data
Horowitz, Michael (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1999-01)Today, deep waters produced in the North Atlantic are exported through the western South Atlantic. Antarctic intermediate water AAJW also enters the Atlantic in this region. Circumpolar deep water (CDW) fills the depths ... -
Carbon dynamics in the western Arctic Ocean : insights from full-depth carbon isotope profiles of DIC, DOC, and POC
Griffith, David R.; McNichol, Ann P.; Xu, Li; McLaughlin, Fiona A.; Macdonald, Robie W.; Brown, Kristina A.; Eglinton, Timothy I. (Copernicus Publications on behalf of the European Geosciences Union, 2012-03-28)Arctic warming is projected to continue throughout the coming century. Yet, our currently limited understanding of the Arctic Ocean carbon cycle hinders our ability to predict how changing conditions will affect local ...