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Plagiogranites in the Coolac ophiolite suite, New South Wales, Australia

Published online by Cambridge University Press:  01 May 2009

P. M. Ashley ,
B. J. Franklin  and
A. S. Ray
P. M. Ashley
Affiliation:
Minerals Department, Esso Australia Ltd, G.P.O. Box 4047, Sydney, N.S.W. 2001, Australia
B. J. Franklin
Affiliation:
Department of Applied Geology, The N.S.W. Institute of Technology, Sydney, N.S.W. 2007, Australia
A. S. Ray
Affiliation:
A. C. I. Technical Centre Pty Ltd, 813 South Dowling Street, Waterloo, N.S.W. 2017, Australia
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Summary

Plagiogranites occur mainly as intrusive bodies and tectonic inclusions within mafic and ultramafic members of the Coolac ophiolite suite. Quartz diorites and trondhjemites appear to represent localized late-stage felsic differentiates of subalkaline tholeiitic magma, with their formation dominantly controlled by fractionation of hornblende and plagioclase. Albitites are interpreted as altered equivalents of quartz diorites and trondhjemites. Chemical data, while emphasizing the similarity of these rocks to ‘oceanic plagiogranite', also indicate that variation in the latter may be broader than previously defined. The Coolac rocks show less marked Fe-enrichment, higher Ni and Cr, and lower Y and Zr than many ophiolitic plagiogranites. These data are consistent with weak calc-alkaline tendencies demonstrated in the Coolac ophiolite suite.

Type
Articles
Information
Geological Magazine , Volume 120 , Issue 1 , January 1983 , pp. 1 - 20
Copyright
Copyright © Cambridge University Press 1983

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References

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