THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 79 



foliation of the country rock. Some are thus true dikes, and others 

 are more properly to be regarded as small sills. The latter are 

 occasionally seen to bifurcate, the individual parts, often several 

 feet in thickness, occupying different horizons in the schists. The 

 most instructive example of this phenomenon is seen one and 

 eight-tenths miles east-northeast of Eddy on the side of a knoll 

 adjacent to the amphibolite border of the granite, where the rela- 

 tions are roughly those shown in the diagram (figure 14). The dike 

 is coarse-grained (crystals one-half to three-quarters of an inch 



a 







b 





c 



d 





e 







/ / 



' / I / / 





5^g 



' ' '<["! ^' 





/><^- 



/// / / / 



////// 



////// 



Fig. 14 Sheared pegmatite dike in Grenville gneiss. The sketch is some- 

 what diagrammatic, but there is small doubt that the dike bifurcates one or 

 more times. (a) Grenville gneiss, weathering rusty; (&) garnet gneiss; 

 (c) amphibolite cut by and injected with granite; ((i) pink granite gneiss 

 with contact halo of amphibolite and garnet gneiss; (<?) sheared white 

 pegmatite cutting rusty gneiss. 



One and eighth-tenths miles east-northeast of Eddy. 



in diameter) at the base, but becomes finer-grained upward; a 

 marked schistosity has in places developed an augen pegmatite 

 gneiss whose deformation is undoubtedly closely related to the 

 strong contortions in the intruded garnetiferous rusty gneiss. 



The pegmatites of this area are remarkably free from those rarer 

 minerals which one is accustomed to regard as at home in this kind 



