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Nature and origin of banding in the granitic sheets Tremearne, Porthleven, Cornwall

Published online by Cambridge University Press:  01 May 2009

Maurice Stone
Maurice Stone
Affiliation:
Department of Geology, University of Exeter, Exeter, Devon.
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Summary

The granitic sheets of Tremearne are believed to have originated from the roof of the Tregonning granite and to have undergone lateral differentiation from leucogranite to aplite with associated pegmatite in a direction away from this granite. Several types of banding are described from the pegmatite-rich region at the Megiliggar Rocks. Some decimetre-scale banding is the result of intrusion of “magmatic” aplitic material, but coarse pegmatite bands are believed to have grown in solid aplite. A close examination of centimetre-scale banding and fine-banding in aplite (line rock) indicates that this is related to pegmatite development and is metasomatic. The mobility of alkalies and the concentration of potash in pegmatite relative to aplite is discussed.

Type
Articles
Information
Geological Magazine , Volume 106 , Issue 2 , 20 April 1969 , pp. 142 - 158
Copyright
Copyright © Cambridge University Press 1969

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