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XII.—The Structure and Form of the Granophyric Quartz-Dolerite Intrusion, Centre II, Ardnamurchan, Argyllshire

Published online by Cambridge University Press:  06 July 2012

R. R. Skelhorn ,
R. W. D. Elwell  and
R. C. Tyler
R. R. Skelhorn
Affiliation:
Department of Geology, Sir John Cass College, London
R. W. D. Elwell
Affiliation:
Department of Geology, King's College, London
R. C. Tyler
Affiliation:
Department of Geology, King's College, London.
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Synopsis

The Granophyric Quartz-dolerite is one of a number of intrusions having arcuate outcrops which are concentric with respect to Centre II, Ardnamurchan. It is composed of three rock types: porphyritic dolerite, aphyric dolerite and granophyre. The granophyre extensively net-veins the two kinds of dolerite. However, the development of the net-veining was only the last stage of its intrusive activity. Relationships between granophyre and aphyric dolerite are such as to indicate that at an earlier stage both were in a magmatic state at the same time; that is, they were intruded together, though movement of granophyre magma persisted after the aphyric dolerite had solidified. Evidence is presented to show that intrusion of the porphyritic dolerite was the first episode, and that this provided the host rock for the simultaneous intrusion of aphyric dolerite and granophyre. In its role as host rock, the porphyritic dolerite was at first incompletely crystallized, but for later intrusions it had consolidated. When both dolerites were solid they were net-veined by the granophyre.

The inner contact of the Granophyric Quartz-dolerite was formed by a later intrusion. The outer contact for much of its extent dips fairly gently outwards, and it would seem that where this is so intrusion was more nearly in a horizontal than a vertical sense. Locally, sheeted relationships between the three members of the Granophyric Quartz-dolerite, being gently inclined, support this conclusion. There are several possibilities as to the form the intrusion might have, and these are discussed.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 66 , Issue 12 , 1966 , pp. 285 - 306
Copyright
Copyright © Royal Society of Edinburgh 1966

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