RELATIONS BETWEEN ZONES OF DEFORMATION. 1013 



It is highly probable that upon the average the openings of the zone of 

 fracture gradually decrease in number and size as depth increases, until in 

 the zone of flowage the openings are, as already explained, microscopic or 

 nonexistent If such a gradation exists, it is a necessary corollary that the 

 deformations of the zone of fracture must have their equivalents in the 

 deeper-seated zone of flowage. This point is fully discussed elsewhere." 

 It is explained that with depth, faults are replaced by flexures, and that 

 any deformation of a large mass of a given rock from one form to another 

 by fracturing may be imitated by similar changes of form in the zone of 

 flowage, the result being there accomplished by granulation of the mineral 

 particles or by their recrystallization, or by both. 



Where rocks have been deformed in the zone of flowage and are now 

 at the surface there is superimposed upon the effects of the deep-seated 

 deformation the deformation by fracture resulting- from earth movements 

 during the time the rock was slowly migrating through the zone of fracture 

 to the surface. 



EFFECTS OF DEFORMATION AND CHEMICAL CHANGES UPON TEMPERATURE. 



It has been pointed out in previous chapters that deformation results 

 in the liberation of heat which may considerably raise the temperature of 

 the rocks. Indeed, Mallett holds (see pp. 99-100) that deformation may 

 actually produce enough heat to fuse the rocks. While I dissent from this 

 conclusion, this view illustrates the importance of the rise of temperature 

 which may follow from mechanical action. 



It has been shown further that a moderate rise in temperature may 

 increase the activity of the solutions to an amazing extent. Indeed, in a 

 chemical laboratory a slight rise in temperature is often sufficient to inau- 

 gurate a reaction which otherwise would not take place, and to increase the 

 speed of the reaction many fold. It is therefore clear that deformation is 

 favorable to the segregation of ore deposits in two different ways, first, by 

 forming openings for a vigorous circulation, and second, by heating the 

 solutions and thereby greatly increasing their activity. 



In the zone of katamorphism the chemical reactions liberate heat, cause 

 an increase of temperature in the zone in which the ores are mainly segre- 



«See Chapter VIII (pp. 776 et seq). See also Principles of North American pre-Cambrian 

 geology, cit., pp. 674-676, 694-698. 



