VOLUME XXXI NUMBER 3 



THE 



JOURNAL OF GEOLOGY 



April-May ig2j 



THE FINAL CONSOLIDATION PHENOMENA IN THE 

 CRYSTALLIZATION OF IGNEOUS ROCK 



R. J. COLONY 

 Columbia University, New York City 



Pyrogenetic processes may, for convenience, be divided into 

 {a) t5ects produced within the igneous rock mass itself, and {h) 

 effects produced by the end-stage consolidation products (aqueo- 

 igneous matters) upon the neighboring rocks into which these 

 matters have been forced. 



The effects produced within the igneous rock itself are due in 

 part to molecular changes taking place in the various individual 

 minerals which crystallize during consolidation, some of them 

 possessing one or more different allotropic forms into which they 

 pass as the temperature of the rock-mass falls through the various 

 critical ranges where such inversions are effected; in part to actual 

 reactions occurring between some of the component minerals of 

 the rock already crystallized and the remaining still-molten magma ;^ 

 and in part to reactions due to adjustments of equilibrium between 

 the extreme end-stage, highly concentrated "mo.ther-liquor" 

 which, by selective freezing, has been enriched with the more 

 volatile gases usually termed "mineralizers," among which water 



^ N. L. Bowen, "The Reaction Principle in Petrogenesis," Jour. Geol., Vol. XXX 

 (1922), pp. 177-98. 



169 



