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Hornblendes from some basic hornfelses in the New England region, New South Wales

Published online by Cambridge University Press:  14 March 2018

R. A. Binns*
Affiliation:
Department of Geology, University of New England

Summary

With progressive increase in grade of contact metamorphism, aluminous hornblendes in some New England basic hornfelses change from a pale blue-green variety with ragged actinolitic habit, to a deeper bluish-green variety, then to a deeply coloured brownish type with granular habit. At all stages the coexisting plagioclase is appreciably calcic. No outer aureole of albite-epidote-actinolite hornfels has been recognized. The higher grade hornblendes are richer in alkalis and titanium, and poorer in octahedrally co-ordinated aluminium than those formed at low grades. Two analysed hornblendes display an unusual excess of calcium, which occupies the Y site, and another has a very high content of ferrous iron and potassium.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1965

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