A microstructural and fabric study of the Galway Granite, Connemara, western Ireland

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doi: 10.1017/S0016756804000378
Authors:Baxter, S.; Graham, N. T.; Feely, M.; Reavy, R. J.; Dewey, J. F.
Author Affiliations:Primary:
National University of Ireland, Department of Earth & Ocean Sciences, Galway, Ireland
University of California at Davis, United States
University College, United Kingdom
Volume Title:Geological Magazine
Source:Geological Magazine, 142(1), p.81-95. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:2005
Note:In English. 46 refs.; illus., incl. sects., geol. sketch maps
Summary:A detailed field and microstructural investigation of mineral fabrics in the late-Caledonian Galway Granite Batholith (approximately 400 Ma) provides insights into the relationship between emplacement-related deformation and crystallization state. These relationships are used to infer the regional instantaneous strain pattern at the time of intrusion. A Marginal Deformation Zone occurs in the granite along part of its northern sector, where planar fabrics are contact-parallel and dip steeply to the north. Within the Marginal Deformation Zone, the granite has similar patterns of pre- and post-RCMP (Rheologically Critical Melt Percentage) fabrics on either side of the NNE-trending Shannawona Fault Zone, which separates the Western and Central blocks of the batholith. Oblate pre-RCMP fabrics, which intensify towards the contact, are overprinted in a down-temperature continuum of deformation by co-axial post-RCMP fabrics that also become more intense towards the contact. At the southern edge of the Marginal Deformation Zone, deformation ceased before the granite reached its RCMP whereas, close to the contact, deformation ceased at approximately c 500°C. Within the Central Block, oblate fabrics also developed parallel with internal granite facies boundaries. Throughout the batholith, the fabrics formed by co-axial deformation as a result of lateral expansion operating in successive magma batches at the emplacement level. These intrusion-related fabrics are consistent with other evidence that indicates the Galway Granite was emplaced into a transtensional setting at the end of the Caledonian Orogeny.
Subsections:General; Igneous petrology
Subjects:Batholiths; Caledonian Orogeny; Crystallization; Deformation; Emplacement; Fabric; Foliation; Granites; Igneous rocks; Intrusions; Orogenic belts; Paleozoic; Petrofabrics; Plutonic rocks; Schistosity; Structural analysis; Style; Syntectonic processes; Tectonics; Connemara; Europe; Galway Granite; Galway Ireland; Ireland; Western Europe; Shannawona fault zone
Coordinates:N532000 N532000 W0093000 W0093000
Abstract Numbers:05M/1506
Record ID:2005027074
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Cambridge University Press, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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