THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 7/ 



As to the possibility of a twofold or multiple invasion of granite 

 in this quadrangle, there is little reason to regard this as capable of 

 substantiation. The normal and uncontaminated granites of all 

 parts of the quadrangle are so nearly identical, and as regards 

 mineral composition and texture vary within such narrow limits, 

 that it is not practical in the field to make any separation or dis- 

 tinction between them. The granite lenticles and sills of the sig- 

 moid area are frequently coarser-grained than the larger masses 

 elsewhere, but as these also grade into the fine-textured normal 

 variety (see plates lo, lower figure, and ii, upper figure), and have 

 the same relations to other formations, it has not been found possi- 

 ble to make any age distinction between them. If they are not 





b 





y^ \ 



— \ 



-vN 



/ 1 



/ , 



/ 



\-\ 



_\' 



/ 



Fig. 12 Dike of white pegmatite cutting amphibolite. (a) Amphibolite ; 

 (6) white pegmatite; (c) surficial covering. 

 One-quarter of a mile south of Harrison creek bridge, left bank of brook. 



exactly synchronous, they at least belong to the same period of early 

 Precambrian granitic invasion. 



Hence if the local relations between the granite and amphibolite 

 as above described are to be interpreted as having any significance 

 at all, they must be regarded as establishing the later age of the 

 pink granite gneisses as a class with respect to the Pyrites and 

 Pierrepont gabbro-amphibolites. This conclusion is supported also 

 by the general abundance of flammen and irregular veins of peg- 

 matitic material in the amphibolite zone of the sigmoid (see plate 

 13, lower figure), in addition to the more normal injected granite; 



