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Silicate mineralogy of the Behelvie cumulates, N E Scotland

Published online by Cambridge University Press:  05 July 2018

W. J. Wadsworth
W. J. Wadsworth*
Affiliation:
Department of Geology, The University, Manchester M13 9PL
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Abstract

Ultramafic, troctolitic and gabbroic rocks at the northern end of the Belhelvie layered intrusion display progressive cryptic variation over a stratigraphic thickness of approximately 800 m in steeply-dipping cumulates, which young from W to E. This variation is shown by olivine (Fo87−77), orthopyroxene (En87−79), clinopyroxene (Ca45Mg48Fe7 to Ca44.5Mg45.5Fe10) and plagioclase (An81−75). The Belhelvie succession is believed to be equivalent to the poorly-exposed and structurally complex Insch Lower Zone. A laterally impersistent hypersthene-gabbro unit within the main sequence is re-interpreted as a downfaulted block of slightly more evolved cumulates. A repeat sequence of peridotites, troctolites and gabbros on the eastern side of the intrusion, and separated from the underlying main succession by a thin septum of country rock, is believed to represent a fresh influx of magma.

Keywords

silicatescryptic variationcumulatesBelhelvieScotland
Type
Research Article
Information
Mineralogical Magazine , Volume 55 , Issue 378 , March 1991 , pp. 113 - 119
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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