The cooling history of Connemara, western Ireland, from K-Ar and Rb-Sr age studies

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doi: 10.1144/gsjgs.145.4.0649
Authors:Elias, E. M.; Macintyre, R. M.; Leake, B. E.
Author Affiliations:Primary:
Univ. Glasgow, Dep. Geol., Glasgow, United Kingdom
Other:
Isot. Geol. Unit, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 145(4), p.649-660. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1988
Note:In English; illus. incl. 4 tables, geol. sketch maps
Summary:K/Ar age determinations are reported on 26 hornblendes, 17 coexisting muscovites and biotites, 9 muscovites and 9 biotites from the Dalradian Connemara schists, metagabbros and gneisses; these are supplemented by 19 Rb/Sr whole-rock-mica ages and four 40Ar/39Ar incremental heating ages on micas. A long (≥75 m.y.) and complex cooling history is indicated. There is an irregular increase of hornblende K/Ar ages (to 480 ± 10 m.y.) with increase of metamorphic grade southwards towards the metagabbros and gneiss. The preservation of the complex cooling pattern is ascribed to the action of syn- and post-metamorphic slides or faults which moved slices of the massif upwards by varying amounts. Rapid cooling (∼30°C/m.y.) at 480 ± 10 m.y. (Arenig-Llanvirn) during a folding phase was followed by slower cooling until 455 ± 10 m.y. (Caradoc), when renewed rapid uplift occurred. Widespread biotite K/Ar and Rb/Sr ages of 440 ± 5 m.y. (end-Ordovician) throughout Connemara and the Dalradian rocks of Scotland are ascribed to the major Taconic event. The importance of very close sampling integrated with structural studies is emphasized. [R.A.H.]
Subjects:Absolute age; Cooling; Dalradian; Dates; Gneisses; History; Inclusions; K/Ar; Metagabbro; Metaigneous rocks; Metamorphic rocks; Ordovician; Paleozoic; Petrology; Rb/Sr; Connemara; Europe; Galway Granite; Galway Ireland; Ireland; Western Europe; Western Ireland
Abstract Numbers:89M/0027
Record ID:1988060144
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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