CRENULATION CLEAVAGE DEVELOPMENT BY PARTITIONING OF DEFORMATION INTO ZONES OF PROGRESSIVE SHEARING (COMBINED SHEARING, SHORTENING AND VOLUME LOSS) AND PROGRESSIVE SHORTENING (NO VOLUME LOSS) - QUANTIFICATION OF SOLUTION SHORTENING AND INTERMICROLITHON-MOVEMENT

An analytical method for determining amounts of cleavage-normal dissol ution and cleavage-parallel shear movement that occurred between adjac ent microlithons during crenulation cleavage seam formation within a d eformed slate is developed for the progressive bulk inhomogeneous shor tening (PBIS) mechanism of crenulation cleavage formation. The method utilises structural information obtained from samples where a divergin g bed and vein are offset by a crenulation cleavage seam. Several samp les analysed using this method produced ratios of relative, cleavage-p arallel movement of microlithons to the material thickness removed by dissolution typically in the range of 1.1-3.4:1. The mean amount of so lution shortening attributed to the formation of the cleavage seams ex amined is 24%. The results indicate that a relationship may exist betw een the width of microlithons and the amount of cleavage-parallel inte rmicrolithon-movement. The method presented here has the potential to help determine whether crenulation cleavage seams formed by the progre ssive bulk inhomogeneous shortening mechanism or by that involving cle avage-normal pressure solution alone.