RECRYSTALLIZATION LAGS BEHIND DEFORMATION. 697 



would show important strain shadows or even granulation. The texture 

 characteristic of the schists (described on pp. 688-690) is itself further 

 evidence of continuous recrystallization during deformation. It is a tex- 

 ture peculiar to the schists. If the minerals were not readjusted in a 

 continuous fashion they must have become granulated by the mechanical 

 forces. If they had become fused into a magma, from that state the 

 material would have recrystallized with textures peculiar to the igneous 

 rocks. The regular arrangement of the mineral particles, with then- 

 longer axes in definite planes is just what would be expected if the con- 

 tained water were taking material into solution and depositing it largely 

 at the borders of the mineral particles, and thus continuously building 

 them out laterally. 



Further evidence that recrystallization may nearly keep pace with 

 deformation is found in the porphyrinic minerals which frequently occur in 

 the schists Some of the more common of these minerals (mentioned on 

 page 700) are garnet, staurolite, andalusite, feldspar, hornblende, chlori- 

 toid, chlorite, and mica. Such porphyritic minerals ordinarily show no 

 perceptible strain. They frequently lie with their longer axes or readiest 

 cleavage across the schistosity. This is true even of mica and chloritoid, 

 the cleavage of the porphyritic constituents cutting directly across the 

 cleavage of the abundant small individuals of mica which accord with 

 the schistosity. It is maintained (p. 702) that such minerals have 

 developed mainly under static conditions after mass movement ceased. 

 These porphyritic minerals seem to be evidence that the differential 

 stresses of static conditions are ordinarily not sufficient to control the 

 orientation of the mineral particles; that in order to do this the differential 

 stresses must be sufficient to produce actual movement throughout the 

 mass of the rocks. If this be so we must suppose that the orientation of 

 the minerals producing schistosity occurred during the movement itself, 

 or, in other words, that recrystallization nearly kept pace with the 

 movements. 



During movement, in some cases the tendency for large individuals to 

 grow at the expense of smaller ones may control, and properly oriented 

 individuals grow to a porphyritic size. For instance, porphyritic feldspars 

 may show a marked tendency toward crystallographic orientation, the 

 cleavages of the feldspars corresponding with the cleavages of the rocks. 



