REACTIONS OF ZONE OF ANAMORPHISM. 169 



As illustrations of the process of silication may be mentioned the 

 formation of wollastonite from pure limestone, of tremolite from dolomitic 

 limestone, of actinolite from ankerite, and of griinerite from siderite. (See 

 pp. 239, 241, 243, 244.) In the impure limestones under deep-seated con- 

 ditions, where numerous bases are present, various complicated silicates 

 form, such as other pyroxenes and amphiboles, tourmaline, chondrodite, etc. 



The process of dehydration involves the liberation of water. This 

 reaction, it is safe to say, is one which is controlled by pressure. The 

 combined water is actually squeezed out of the hydrated mineral particles, 

 transforming- them to less hydrous and to anhydrous forms in a manner 

 similar to that in which free water is pressed from a sponge. 



Whether or not pressure in the zone of anamorphism is sufficient to 

 deoxidize compounds is uncertain. Certainly it can not be asserted that 

 the pressure is sufficient to squeeze out a part of the oxygen of hematite, 

 thus transforming it to magnetite. So far as deoxidation occurs, probably 

 the oxygen abstracted from the rocks usually unites with the elements of 

 organic compounds, thus producing carbon dioxide and water. Thus the 

 chief products liberated by silication, dehydration, and deoxidation are car- 

 bon dioxide and water. These join the interstitial water in the subcapillary 

 spaces and probably slowly escape into the zone of katamorphism above. 

 (See pp. 665-667.) This results in loss of material, and since the specific 

 gravity of the minerals is increased on the average, the volume of the 

 rocks is decreased. 



Besides the above processes, condensation may also be accomplished 

 by recrystallization, although this process generally takes place in connec- 

 tion with them. The process of recrystallization produces a rearrangement 

 of the elements in such a way as to form compounds of higher specific 

 gravity. This is well illustrated by the devitrification of glass. 



The minerals produced in the zone of anamorphism are numerous, 

 definite, stable, crystalline, of high specific gravities, and probably have 

 complex molecules. The rocks formed are compact and strong. The 

 lower zone may therefore properly be called the zone of anamorphism, or 

 anamorphic zone. This use of the term anamorphism is parallel to the use 

 of the term anabolism in biology to designate those chemical changes in a 

 living body which result in the production of complex compounds from more 



