Abstract

Simple two-dimensional techniques are used to make an estimate of the total shortening across a narrow greenstone belt in northwestern Ontario. The techniques are based on the basic principle of restoring the predeformational geometry of a horizontal traverse across the belt. Depending on the technique used this traverse is a string of line elements or a chain of finite elements. The strain ratios available for the restoration are minimal values and need to be increased significantly to obtain realistic results. Depending on the strain values selected for the restoration, amounts of horizontal shortening range from 17 to 49%. The actual amount remains unknown, but is thought to be < 50%.In view of the apparent variation in longitudinal strain along the greenstone belt, a three-dimensional treatment seems to be necessary. This would require that strain measurements be taken systematically throughout, rather than along a single traverse across, a greenstone belt segment.

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