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V.—On certain Gneisses with Round-grained Oligoclase and their Relation to Pegmatites

Published online by Cambridge University Press:  01 May 2009

George Barrow
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Extract

In the course of my work in the Highlands of Forfar, I have been much struck with the mode of occurrence of certain light-coloured gneisses, of undoubted igneous origin.

They are intruded into the surrounding rocks in an infinite number of thin bands or sills, generally interlacing, and often not more than two feet thick; sometimes not exceeding an inch. Their bulk in some areas exceeds considerably that of the older rocks, at other times it is far less.

Two points are easily noted; first, they have no selvage edge; secondly, they have a very characteristic aspect, due to rounded grains of oligoclase.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 2 , February 1892 , pp. 64 - 65
Copyright
Copyright © Cambridge University Press 1892

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References

1 See Prof. Sollas’ paper, “Contributions to a Knowledge of the Granites of Leinster,” Trans. Eoy. Irish Acad. vol. xxix. p. 427.Google Scholar