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Multiple intrusive phases in the Leinster Batholith, Ireland; geochronology, isotope geochemistry and constraints on the deformation history

Tobias Fritschle, J. Stephen Daly, Martin J. Whitehouse, Brian McConnell and Stephan Buhre
Multiple intrusive phases in the Leinster Batholith, Ireland; geochronology, isotope geochemistry and constraints on the deformation history
Journal of the Geological Society of London (October 2017) 175 (2): 229-246

Abstract

The formation of granite batholiths, commonly by incremental assembly of small magma batches, and their correlation with tectonic events, on both local and regional scales, is crucial to understanding the evolution of the Earth's continental crust. However, these correlations often rely on assumptions about the detailed relationship and timing of mapped units. Here we report how an integrated geochronological, structural and isotope geochemical study in only one key locality from the late Caledonian Leinster Batholith in SE Ireland provides the potential for unravelling essential questions on batholith petrogenesis. The Northern Unit of the Leinster Batholith intruded incrementally, as demonstrated by three crosscutting granite varieties at Glenmacnass Waterfall. The oldest, foliated granite, yielded a zircon U-Pb age of 417.4 + or - 1.7 Ma. Following deformation, equigranular granite intruded at 409.8 + or - 1.9 Ma and was cut by megacrystic granite at 404.9 + or - 2.6 Ma. Hence, batholith formation lasted up to 16.8 myr, challenging the widely accepted 405 Ma age for the entire batholith. Multi-isotope geochemical investigations permit derivation of the three granites from the same sources, including both Mid- to Upper Ordovician peri-Gondwanan arc-related magmatic and Lower to Mid-Ordovician Ribband Group metasedimentary rocks. Zircon inheritance and Lu-Hf isotope geochemistry also reveal reprocessing of older granite wall rock in the younger magmas. Supplementary Material: Data tables are available at https://doi.org/10.6084/m9.figshare.c.3898330


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 175
Serial Issue: 2
Title: Multiple intrusive phases in the Leinster Batholith, Ireland; geochronology, isotope geochemistry and constraints on the deformation history
Affiliation: University College Dublin, School of Earth Sciences, Dublin, Ireland
Pages: 229-246
Published: 20171012
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 122
Accession Number: 2017-090073
Categories: Igneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N52°55'00" - N53°04'60", W06°34'60" - W06°15'00"
Secondary Affiliation: Swedish Museum of Natural History, SWE, SwedenIreland, Geological Survey, IRL, IrelandJohannes Gutenberg-Universitaet, DEU, Germany
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201747
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