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

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.

This publication has 6 references indexed in Scilit: