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Epitaxic relations between coexisting pyroxenes

Published online by Cambridge University Press:  05 July 2018

J. Tarney
J. Tarney*
Affiliation:
Department of Geology, The University, Birmingham 15
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Summary

Many examples of epitaxic relations between coexisting pyroxenes are found in the picritic dykes that cut the Lewisian gneisses of the Lochinver area, Sutherland. In some dykes augite forms oriented overgrowths on the (100) face of orthopyroxene; in others orthopyroxene forms similar overgrowths on augite. A number of unusual variants of the first case are described together with a complex ‘induced’ twinning found in the augite overgrowths. Analyses of the coexisting pyroxenes suggest that the overgrowth relation has been facilitated by increased solid solution between the pyroxenes, so reducing the crystallographic misfit along the c-axis. However, crystallization of the pyroxenes in an ordered sequence rather than simultaneously also seems to have been an important factor.

Type
Research Article
Information
Mineralogical Magazine , Volume 37 , Issue 285 , March 1969 , pp. 115 - 122
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1969

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