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Constraints on the development of magmatic layering in a syntectonic mafic-ultramafic suite, NW Connemara, Ireland

B. O'Driscoll, D. G. R. Powell and R. J. Reavy
Constraints on the development of magmatic layering in a syntectonic mafic-ultramafic suite, NW Connemara, Ireland
Scottish Journal of Geology (November 2005) 41, Part 2: 119-128

Abstract

The Dawros-Currywongaun-Doughruagh Complex of NW Connemara comprises a deformed and metamorphosed suite of syntectonic mafic to ultramafic intrusions within folded, lower amphibolite grade metasediments of the Dalradian Supergroup. Field observations and thin-section petrography have identified examples of exceptionally well-preserved modal layering and primary igneous (cumulus) textures in central areas of two of the intrusions (Dawros and Currywongaun), together with macroscopic graded bedding, slumping, and scour structures that allow layer formation to be attributed to magmatic sedimentation. Layering is occasionally chaotically folded and deformed, and as evidence of associated solid state or plastic deformation is absent, this is thought to be due to synmagmatic deformation. A magmatic fabric that is observed almost everywhere throughout the intrusions generally increases in intensity towards their margins, giving a poorly defined internal strain zonation in both. The presence of layering in these relatively small syntectonic intrusives offers insights into the way that magma chamber processes operate in tectonically active environments by highlighting the structural and petrological constraints these environments impose on layer development. This has significant implications for perceived restrictions on layer development in terms of the types of intrusions they develop in.


ISSN: 0036-9276
EISSN: 2041-4951
Coden: SJGEAX
Serial Title: Scottish Journal of Geology
Serial Volume: 41, Part 2
Title: Constraints on the development of magmatic layering in a syntectonic mafic-ultramafic suite, NW Connemara, Ireland
Affiliation: Trinity College Dublin, Department of Geology, Dublin, Ireland
Pages: 119-128
Published: 20051101
Text Language: English
Publisher: Scottish Academic Press, Edinburgh, United Kingdom
References: 29
Accession Number: 2006-055368
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 plate, geol. sketch maps
N53°15'00" - N53°40'00", W10°19'60" - W09°00'00"
Secondary Affiliation: University College Cork, IRL, Ireland
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200615
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