THE PRECAMBRIAN ROCKS OP THE CANTON QUADRANGLE 83 



the garnet gneiss are cut at right angles by tourmaHne-bearing 

 quartz-orthoclase pegmatite veins (see figure 17), sometimes 

 sheared, which are altogether separate and independent from the 

 other pegmatites and evidently belong to a later period or phase of 

 granitic activity. Though parallel at this point to the average 

 trend of formations (northeast), they cut directly across, or inter- 

 cept at a large angle, the boundaries of the interbanded strips of 

 garnet gneiss, amphibolite and granite-pegmatite. This peculiarity 



/ N" 





i'.-«'; 



Fig. 17 Granite-ainphibolite injection gneiss cut by tourmaline-pegmatite 

 dike. Such dikes are as a rule perpendicular to the older formations, what- 

 ever orientation these may have, (a) Amphibolite; (b) fine-grained pink 

 granite gneiss; (c) tourmaline-pegmatite dike, two or three inches thick. 

 Left is w^est, right is east. 



Same locality as shown in figure 16. 



of high-angle intersection is common to most of the dikes of this 

 class, and together with their clearly defined boundaries and ina- 

 bility to produce intimate injection, serves as a basis for regarding 

 them as to distinct though not widely differing age from those 

 previously described. An interesting group of these dikes is found 

 on the west side of the Canton belt of granite, one and three-fifths 

 6 



