Quantitative structural analyses and numerical modelling of ...

PRECURSOR AND RHEOLOGY OF VARISCAN GRANULITES 119Fig. 12. Quantitative microstructuralanalysis of the degree of grain boundarypreferredorientation v. contact frequenciesfor like and unlike boundaries of feldspars.Numbers at individual data points refer tothe evolution stages defined in the sectionGranular microstructures.Fig. 13. Crystal size distribution curves for both feldspars. Values of slope and upper intercept of linear regression are plotted togetherin the inset showing an evolutionary trend for both the feldspars. Numbers at individual data points refer to the evolution stagesdefined in the section Granular microstructures.whereas the like–like contacts are negative where thephases tend to be regularly distributed.Crystal size distributions measured in metamorphicrocks yield quantitative information about crystalnucleation and growth rates, growth times and thedegree of overstepping of reactions during metamorphism(Cashman & Ferry, 1988). The CSDs aredescribed as the population density function of thecumulative number of crystals per unit volume perlinear crystal size. The data are plotted in log-normalspace and a linear regression of points is the characteristic.The intercept values (N0) are proportional tothe nucleation density of the examined phase at theonset of nucleation (size 0), and the slope (Gt) is proportionalto the modification of original grain-sizedistribution by a variety of coarsening processes suchÓ 2010 Blackwell Publishing Ltd357