312 VAN HISE—METAMORPHISM OF ROCKS AND ROCK FLOWAGE. 
granulation. The slower the deformation the more likely is the read- 
justment to be by recrystallization. 
ZONE OF COMBINED FRACTURE AND FLOWAGE 
In the middle zone of combined fracture and flowage, the alterations 
may combine those of fracture and of flowage. Preparatory to under- 
standing the phenomena in this zone, we may consider ourselves as seeing 
the phenomena of deformation in an imaginary rock of homogeneous 
character, composed of a single mineral which extends from the surface 
to an indefinite depth. Near the surface the rock is broken into blocks 
by faults and joints. There is no marked deformation of the individual 
particles, except in thin layers along the fractures. The textures of the 
rocks are for the most part preserved. Deeper down the fractures are 
closer together, and at sufficient depth the layers may be no thicker than 
leaves. Still deeper down every particle takes part in the deformation. 
This is the zone in which granulation is predominant, although with it 
there may be some recrystallization. Still deeper down recrystallization 
is more and more important, and when this process becomes dominant a 
coarsely crystalline schist is produced. It is therefore clear that there is 
every gradation between the phenomena of deformation of the various 
zones. 
The transition above described for a single formation takes place at 
different depths for different formations and for different minerals of the 
same formation, and hence it is that in heterogeneous formations all of 
the phenomena discussed under both the zone of fracture and the zone 
of flowage occur close together. 
At a given depth the stronger or less readily recrystallized rocks may 
be largely deformed by fracture, and the weaker or more readily recrys- 
tallized rocks be largely deformed by flowage. The result is that original 
textures and structures may be more or less preserved in the former, while 
in the adjacent layers original textures and structures may be entirely de- 
stroyed and the rocks become crystalline schists. It very often happens 
that the alternating beds which show original textures and structures and 
those in which they are obliterated may not be more than a few inches 
thick. 
In the intermediate zone many of the beds are deformed by combined 
mass fractures and fractures of the individual mineral particles, so that 
in the same rock in which joints, faults, fissility, etcetera, and the alter- 
ations attending these phenomena occur, there are also found between 
the major fractures all grades of deformation by interior movement, from 
the earliest stages of peripheral granulation of the grains to complete 
granulation or recrystallization extending throughout the mineral parti- 
