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A Pre-Cambrian Glass from St. Alexis-des-Monts, Quebec *

Published online by Cambridge University Press:  01 May 2009

A. R. Philpotts
Affiliation:
A. R. P. Department of Mineralogy and Petrology, Cambridge.
J. A. Miller
Affiliation:
J. A. M. Department of Geodesy, and Geophysics, Cambridge.

Abstract

The Pre-Cambrian rocks north of Three Rivers, Quebec, are cut by a major fault in which glassy pseudotachylites have been developed. The glass, which is dark brown in thin section, has a specific gravity of 2.76 and a refractive index of 1.567. It has a similarcomposition to the quartz monzonite in which it occurs. Absolute dating by the potassium-argon method indicates that the glass is 975 million years old. The persistence of thisglass indicates how sluggish devitrification can be when the environment is cool and dry.

Type
Articles
Copyright
Copyright © Cambridge University Press 1963

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Footnotes

*

Published by permission of the Deputy Minister, Department of Natural Resources, Quebec, Canada

References

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