CIRCULATION IN ZONE OF FLOW AGE. 1G29 



they approach those of subcapillary size which are characteristic of the 

 zone of flowage. But because of variations in the nature of the rocks 

 this change does not take place uniformly, but irregularly. Hence one 

 would expect that in formations where the deformation is mainly by 

 fracture the movement of the water would be similar to that of the zone of 

 fracture, but less vigorous, and that where the deformation is mainly by 

 flowage the movement of the water would be unimportant. 



CIRCULATION IN ZONE OF FLOWAGE, OR ZONE OF ANAMORPHISM. 



In the zone of flowage, which corresponds to the zone of anamorphism, 

 the circulation of water is very different from that in the belt of cementa- 

 tion. While much of the water in the upper parts of this zone is probably 

 liquid, in the deeper parts of it, and in those parts where recent orogenic 

 movements or great batholithic intrusions have occurred the solutions prob- 

 ablv reach a temperature higher than 365°, and therefore are in the gaseous 

 condition. 



The openings of the zone of anamorphism are for the most part sub- 

 capillary and discontinuous. They are not only small in size, but small in 

 total volume. In the zone of anamorphism, therefore, the quantity of free 

 water at any one time is very small as compared with the zone of fracture. 

 So far as the solutions in the zone of anamorphism are aqueous they are 

 mainly glued to the walls of the subcapillary openings, and the circulation 

 under conditions of quiescence is extremely slow. If there were no addi- 

 tions to the free water, doubtless the circulation would be unimportant so 

 far as ores are concerned. But it is shown (pp. 662, 679-680) that one 

 of the most characteristic reactions of the metamorphism of this zone 

 is liberation of the combined water by dehydration, thus continually 

 adding to the amount of free water. It is certain that this excess of free 

 water is squeezed out of the zone of anamorphism, and it is shown 

 (pp. 665-667) to be highly probable that the major movement of this 

 liberated water is upward into the zone of fracture rather than downward 

 into the centrosphere. This highly heated water carries with it carbon 

 dioxide liberated by the process of silication and as much mineral material 

 as it is able to transport. 



This upward movement may be largely as gaseous rather than as 

 liquid solutions. So far as this is true the laws of these solutions apply 

 rather than those of aqueous solutions. 



