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Petrofabrics of laminated gabbros from the Centre 3 igneous complex, Ardnamurchan, Scotland

Published online by Cambridge University Press:  05 July 2018

N. J. Fortey
N. J. Fortey*
Affiliation:
Institute of Geological Sciences, 64-78 Gray's Inn Road, London WCI X 8NG
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Summary

Petrofabric analysis of five specimens of laminated gabbro from the Centre 3 igneous complex, Ardnamurchan, was carried out by measuring orientations of grains of plagioclase, olivine, and augite with a Universal-stage. Linear alignments of primary precipitate mineral grains within the laminar fabrics were revealed by plots of data for coexisting plagioclase and olivine or augite. The plagioclase grains involved have tabular forms elongated parallel to their a-axes (rather than their c-axes). The olivine grains have flattened ovoid forms and the augite grains have sub-ophitic forms developed about prismatic primocrysts. In all specimens plagioclase displayed alignment of long grain-axes directed approximately down the dip of the lamination, save for one case in which a weak oblique alignment was observed. These lineations were reproduced by accompanying olivine and augite. The alignments are tentatively ascribed to flowage of a viscous boundary zone to the magma body in which crystal growth was taking place.

Type
Research Article
Information
Mineralogical Magazine , Volume 43 , Issue 332 , December 1980 , pp. 989 - 994
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1980

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