38 Canadian Record of Science. 



SUMMARY. 



In the writer's opinion, the following conclusions may 

 be drawn from the foregoing pages : 



The district exhibits a development of Grenville lime- 

 stone pierced by intrusions of gneissic granite which con- 

 tain masses of dioritic rock. 



Considerable deformation took place during the 

 intrusion. 



Between the limestone and the granite is a highly brec- 

 ciated zone, holding large amounts of lime-rich silicates 

 which are eminently characteristic of contact meta- 

 morphism. 



Diagenesis took place. 



To a great extent, however, the elements, other than the 

 lime necessary for the formation of these minerals, came 

 from the intrusion and its accompanying exhalations. 



The metamorphism, then, was largely also metasomatic. 



In the gray gneisses and in the granite are dark basic 

 masses which represent fragments broken off from the 

 limestone series and floated away into the igneous mass 

 They have been still more highly metamorphosed than the 

 rocks from which they came, and have been more or less 

 dissolved and changed in character by the granite. In 

 other words, they have been partially " granitized." 



The gray gneisses, which have the composition of 

 quartz diorites, may represenD an intermediate phase of 

 this " granitization " — between the inclusions and the 

 granite. This theory may account for the large amount 

 of plagioclase feldspar found in the granite itself. 



Dr. Adams is now making a more extended examination 

 of the rocks of this area, working on a greater number of 

 specimens, from a wider range of localities, and it is 

 expected that his studies will throw additional light on 

 the actual processes which have been at work. 



Petrographical Laboratory, 



McGill University, Montreal. 



