Figure G-39 shows a dike and sill complex in which a competent rock, colored black, has intruded into a schist. The horizontal lines represent cleavage in the schist. Consider the cleavage planes to be perpendicular to the minimum principal strain axis. Assume that all structures formed during the same deformational event.

1. What has been the approximate extension e perpendicular to the cleavage?

2. What has been the approximate extension e parallel to the cleavage?

3. Using the two extensions just determined and the structures seen in the dikes and sills, draw a properly proportioned and properly oriented strain ellipse for this rock. Label the zoneswithin the strain ellipse, and give the 1 + e₁: 1 + e₂ ratio.

4. Indicate the zone of the strain ellipse into which each of the two diagonal dike segments falls, and discuss briefly the strain history implied for each.

Figure G-39