CLEAVAGE, CRENULATION

Crenulation Cleavage is formed due to microfolding of an existing foliation (commonly a slaty or phylitic cleavage or schistosity), typically due to shortening of foliation along an axis parallel to its layering. The processes involved are initial pressure solution, followed by establishment of chemical gradient and ionic transfer. The material in the limbs of gentle buckles goes into solution and migrates to the hinge region, this being the easiest direction for such a transfer and at advanced stages, the one in the hinge region partially migrates to limb areas. The hinge zones are quartz rich while limbs get enriched in the phyllosilicate minerals.