CONDITION OF WATER IN BELT OF CEMENTATION. 569 



it is conceivable that as a result of deformation itself the temperature of 

 the rocks may become so high as to convert the water present into the form 

 of gas, but, from investigations upon metamorphism, it is believed to be 

 probable that this condition of affairs rarely obtains, since, as shown on 

 pages 690-692, long before the critical temperature of water is reached 

 solution and deposition of rock material, or recrystallization, readily takes 

 place, and in this change the work converted into heat is far less than in 

 mechanical granulation. 



In conclusion the general statement may be made that in the belt 

 of cementation water is commonly in the form of liquid, and only excep- 

 tionally in the form of gas. 



AMOUNT OF WATER IN BELT OF CEMENTATION. 



It has already been suggested that the belt of cementation might be 

 called the belt of saturation. This implies that the openings in the belt of 

 cementation normally are filled with water solutions; therefore, the answer 

 to the question as to the amount of openings in the belt of cementation 

 approximately answers the question as to the amount of water there 

 contained. It has been seen that in the belt of weathering the openings 

 vary from a small amount to 40 or 50 per cent or more. In the belt of 

 cementation the amount of pore space varies from zero to a maximum as 

 high as 28.28 per cent, the actual amount of pore space found by Buckley 

 in the Dunnville sandstone of Wisconsin. The mechanical sediments, 

 especially sandstones which have not been much cemented, contain very 

 large amounts of pore space. The volcanic fragmental rocks also furnish 

 considerable pore space. The very dense rocks, especially the plutonic 

 igneous rocks, have a very small amount of pore space unless they have 

 been fractured. Wherever the rocks have been deformed above the zone 

 of anamorphism fractures of all classes are produced, including joints, 

 faults, bedding partings, fissility, and brecciation fractures. The amounts 

 of openings which are thus produced may vary from a fraction of a per 

 cent to as large a per cent as in the porous sandstones, as, for instance, in 

 breccias. But the openings which originally existed in the rocks or which 

 have been produced by deformation are in all stages of cementation. Also 



a Buckley, E. B., Building and ornamental stones of Wisconsin: Bull. Geol. and Nat. Hist. Survey 

 Wisconsin No.- 4, 1898, table v, p. 403. 



