RELATIONS OF GRANULATION AND RECRYSTALLIZATION. 737 



The mechanical process of welding can not take place without strain within 

 the elastic limit. Strain beyond the elastic limit can not occur without 

 strain within the elastic limit and welding. Therefore, where the former 

 occurs all the mechanical processes are involved. The chemical processes 

 of cementation and metasomatism do not occur separately; where one takes 

 place the other is sure to be active. These processes, together, go on with 

 or without injection. But injection, which involves both mechanical and 

 chemical factors, never takes place without involving one or two or all of 

 the other processes. Where it takes place on a large scale it is sure to 

 include all the mechanical processes. Moreover, under such circumstances 

 the exomorphic alterations involve the chemical transformations of cemen- 

 tation and metasomatism on a great scale. 



From the foregoing it follows that in most instances of alteration in the 

 zone of anamorphism it is impracticable to state the relative importance of 

 the mechanical processes among themselves or of the chemical processes 

 among themselves. However, the chemical processes, as a group, and the 

 mechanical processes, as a group, can be better compared. As has been 

 noted, the mechanical processes where important usually produce granula- 

 tion, and the chemical processes where important result in recrystallization; 

 but also mechanical action promotes chemical action. The importance of 

 the relations of these two classes of processes demands full consideration. 



RELATIONS OF GRANULATION AND RECRYSTALLIZATION. 



In a rock the same mineral may be partly granulated and partly 

 recrystallized. Even the individual grains of a mineral may exhibit the two 

 processes in various proportions. In this case the fracturing may be along 

 the borders of the individuals, may extend entirely across them, or may 

 granulate them throughout. The simultaneous solutions and depositions 

 may occur along the borders of the original or the secondary granules, or 

 within the spaces produced by the fracturing, or may regenerate the old 

 mineral particles throughout. Any of the deposited material may occur as 

 independent individuals or as enlargements of original grains or mechan- 

 ical granules. Thus, in the different particles of the same mineral in a 

 given rock granulation or recrystallization may be the dominant process. 

 If this be so, the same is true, to an even greater extent, of the particles of 

 different minerals. 



mon xlvii — 04 47 



