HR: 11:50h
AN: T42A-07    [Abstracts]
TI: New geochemical and isotopic constraints on magmagenesis in an Ordovician arc-continent collision, Ireland: The Tyrone Igneous Complex
AU: * Draut, A E
EM: adraut@usgs.gov
AF: U.S. Geological Survey, 400 Natural Bridges Dr., Santa Cruz, CA 95060, United States
AU: Clift, P D
EM: p.clift@abdn.ac.uk
AF: Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen, AB24 3UE, United Kingdom
AU: Hannigan, R E
EM: HANNIGAN@astate.edu
AF: Department of Environmental Science, Arkansas State University, Jonesboro, AR 72401, United States
AU: Blusztajn, J
EM: jblusztajn@whoi.edu
AF: Woods Hole Oceanographic Institution, (WHOI), Woods Hole, MA 02543, United States
AU: Amato, J M
EM: amato@nmsu.edu
AF: Department of Geological Sciences, New Mexico State University, Las Cruces, NM 88003, United States
AU: Schouten, H
EM: hschouten@whoi.edu
AF: Woods Hole Oceanographic Institution, (WHOI), Woods Hole, MA 02543, United States
AB: The Tyrone Igneous Complex (TIC) of County Tyrone, Northern Ireland, has previously been identified as an ophiolite dating to 471 Ma. Although this age suggested along-strike equivalence with igneous and volcaniclastic units of Connemara and the South Mayo Trough in western Ireland, no detailed petrologic or geochemical analyses were previously available from the TIC to substantiate this inference. We present new trace-element and Nd isotopic analyses from 37 spatially and lithologically comprehensive samples of the TIC, including gabbros, basaltic sheeted dikes, a tonalite pluton, and felsic lavas. The geochemical affinity of these samples compares favorably to western Irish plutons and volcanogenic sediments of similar age. Felsic TIC units, in particular, display rare-earth-element enrichment and other trace-element patterns (including relative high-field- strength-element depletion) characteristic of supra-subduction-zone magmatism. Together, the TIC and western Irish units correspond to pre-, syn-, and post-collisional phases of an Early Ordovician collision between an intra- oceanic island arc and the Laurentian continental margin during the closure of the Iapetus Ocean. The new data improve constraints on the magmatic evolution and timing of tectonic events (e.g., initial collision, subduction of continental sediment) within an evolving arc-continent collision zone, processes important for the production of continental crust.
DE: 8104 Continental margins: convergent
DE: 8178 Tectonics and magmatism
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting