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Scapolite compositional change in a metamorphic gradient and its bearing on the identification of meta-evaporite sequences

Published online by Cambridge University Press:  01 May 2009

T. A. P. Kwak
T. A. P. Kwak
Affiliation:
Department of Geology, La Trobe University, Bundoora, Victoria, Australia
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Summary

Scapolite occurs in the NE Mt Lofty area of South Australia in rocks of bulk compositions as diverse as sulphide-rich veins, meta dolerite, scapolite (pelitic) schists, calc-silicate rocks and impure marbles. Scapolites analysed from all these rocks show with increasing grade a linear to near-linear change in composition from Me50 and Me66. Some scatter around these values is attributed to local perturbations of fCl/fCo2 in the fluid phase during metamorphism. Sulphur values as SO3 are below the 0.02 level even when scapolite occurs in contact with sulphides in a vein in a small copper mine; here, however, an interpreted FeO value of 2.58 weight % was recorded. The values in this study are comparable with those of Heitanen (1967), and are believed to be representative of products of normal metamorphic fluids evolved from non-evaporitic metamorphic rocks under a greenschist–amphibolite facies gradient; they can thus be used as a standard in assessing the possible significance of meta-evaporites in other areas.

Type
Articles
Information
Geological Magazine , Volume 114 , Issue 5 , September 1977 , pp. 343 - 354
Copyright
Copyright © Cambridge University Press 1977

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