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Regional and tectonic implications of parallel Caledonian and Permo-Carboniferous lamprophyre dyke swarms from Lismore, Ardgour

Published online by Cambridge University Press:  03 November 2011

M. A. Morrison
Affiliation:
Department of Geological Sciences, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, U.K.
G. L. Hendry
Affiliation:
Department of Geological Sciences, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, U.K.
P. T. Leat
Affiliation:
Department of Geology, Imperial College of Science and Technology, Prince Consort Road, London, SW7 2BP, U.K.

Abstract

Geochemical data are presented for 166 minor intrusions collected across the axis of the Ardgour swarm in the Isle of Lismore. The intrusions can be divided into: an alkali basalt-camptonite-monchiquite group resembling other Scottish Permo-Carboniferous dykes; a group of calc-alkaline (shoshonitic) lamprophyres, diorites and porphyrites with affinities to the late Silurian-early Devonian appinite suite of Scotland; and Tertiary dolerites. The different groups cannot be unambiguously distinguished in the field and secondary alteration precludes petrographic division in many cases. The data indicate that Caledonian and Permo-Carboniferous lamprophyres have probably been confused in previous accounts of dyke distributions in the region. In Lismore the two groups have identical azimuths but the Caledonian intrusions appear to have a greater aggregate volume. The implications for tectonic and regional models of the area are discussed.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1987

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