The geology of the Roundstone ultrabasic complex, Connemara

Saved in:
Authors:Bremner, D. L.; Leake, B. E.
Source:Proceedings of the Royal Irish Academy, Section B: Biological, Geological and Chemical Science, 80(20), 39p. Publisher: Royal Irish Academy, Dublin, Ireland. ISSN: 0035-8983
Publication Date:1980
Note:In English. 24 refs.
Summary:This highly metamorphosed syntectonic intrusion has five principal components, given in order of age: 1) peridotite lumps from a disrupted early layer (with rare harrisite and orbicular structures) enclosed in basic bytownite to anorthite-bearing metagabbro, collectively called the Errisbeg group; 2) more differentiated metagabbros (the south-east gabbros) which enclose Errisbeg group rocks as xenoliths and grade eastwards into 3) the still more differentiated epidiorite group of amphibolites which also inject and stope off Errisbeg group rocks. The epidiorite group is itself soaked and injected by a filter-pressed or immiscible differentiate which crystallized as a separate, slightly later phase; 4) the quartz diorite gneiss, which grades into 5) granitic gneiss. The structure and igneous history have been unravelled by detailed mapping; 131 rocks were analysed for major and trace elements, with 153 microprobe analyses of minerals, including olivine (Fo80-?90), orthopyroxene (En80), plagioclase (up to An96), amphiboles and clinopyroxenes. During folding and metamorphism, the Errisbeg group rocks were rolled or balled up in an envelope of younger differentiates so that the overall structure of the thrice-folded body is a near-recumbent, slightly downward-facing anticline, with the SE gabbros and the epidiorite group being inverted, the structure pre-dating the final consolidation of the quartz diorite gneiss. [T.R.]
Subjects:Genesis; Geochemistry; Gneisses; Igneous rocks; Intrusions; Layered intrusions; Metagabbro; Metaigneous rocks; Metamorphic rocks; Mineral composition; Peridotites; Petrology; Plutonic rocks; Trace elements; Ultramafics; Connemara; Europe; Galway Ireland; Ireland; Western Europe; Ballyconneely Amphibolites; Epidiorite Group; Errisbeg Group; Roundstone
Coordinates:N532500 N533000 W0095000 W0101000
Abstract Numbers:83M/0811
Record ID:1982004644
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
Tags: Add Tag
No Tags, Be the first to tag this record!