THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 75 



granite in the Canton quadrangle may appear as an unnecessary at- 

 tempt to demonstrate the obvious. It nevertheless serves the pur- 

 pose of showing how, in the absence of definite and specific intrusive 

 phenomena, more indirect evidence and general analogies must be 

 used to estabUsh its true character. 



The determination of the relative ages of the gabbroic and 

 granitic intrusions rests on an even more indefinite basis, and for the 

 same reasons as those that obscure the structural relations between 

 the granite and Grenville. In the western half of the sheet the 

 two formations are never found in contact, but the gabbro in the 

 Pyrites and adjacent vicinity is found squeezed in between the 



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Fig. II Granite gneiss cutting and including fragments of amphibolite; 

 the filling between the broken parts of the inclusion has a tendency to 

 become pegmatitic, but such material grades into ordinary granite gneiss, 

 (a) Pink granite gneiss grading into {h) , quartz-orthoclase pegmatite; 

 (c) amphibolite country rock and xenoliths ; {d) surficial covering. Look- 

 ing east. 



One and four-tenths miles southwest of Pierrepont, right bank of brook. 



granite masses. In the Pierrepont or sigmoidal area, on the other 

 hand, the association has the very intimate character of an injec- 

 tion gneiss, as already described. The two rocks are found inter- 

 banded with each other in a conformable manner and, except in 

 the instance now to be described, do not exhibit structural rela- 

 tionships which allow the later intrusive to be distinguished from its 

 country rock, 



