GEOLOGY OF THE NORTH CREEK QUADRANGLE 



19 



per cent of quartz. By becoming coarse-grained and porphyritic 

 it also passes gradually into the granite porphyry. As in the case 

 of the syenite, the contact against the Grenville is seldom sharp 

 except along the lines of faulting. The area covered by the granite 

 is almost the same as that of the syenite or about two-ninths of 

 the quadrangle. 



This rock, too, is decidedly variable as regards color, granu- 

 larity, structure and mineral composition. The colors range 

 through greenish gray, light gray, and pinkish to almost red. These 

 color varieties are especially well shown in the vicinity of The 

 Glen. Pinkish granites are the most abundant. 



The granularity of the rocks varies from fine to coarse grain, 

 with a medium grain predominating. Coarse-grained types often 

 show a tendency toward porphyritic texture and thus approach the 

 granite porphyry. The granites are almost always highly granu- 

 lated, especially the more gneissoid varieties in which the feldspars 

 are most badly crushed. There is a wide range from poorly 

 gneissoid rocks to those which are highly foliated and almost 

 banded, the latter being particularly true of the commonly occur- 

 ring pink granites. 



The range in mineral composition is well illustrated by the se- 

 lected examples given in table 2. As compared with the granitic 

 syenite, the chief differences are the high quartz content, the com- 

 mon occurrence of microcline, the generally lower content of horn- 

 blende, and the almost constant presence of biotite. 



TABLE 2 

 Granite 









(U 







1 



1 













































•s 



"i 



J= 



<u 



ttJ 























"« 











c 

 







K 



3 



<u 



V 



4-> 



c 



« 







d 



J3 

 u 

 









(30 



at 



3 

 



^ 



K 







(5 



.i2 

 c5 









S 



a 

 < 













01 



















I 



21 



22 



22 





7 

 01 



26 



20 



2 







little 



I 













"> 



35 



7 



30 



18 



3 



28 



8 



I 



1 

 2 



3 



I 



t 



I 



I 



4 



3 



tS 



17 



50 







30 





2 







littk" 



I 









oi-And 

















4 



53 1 



10 



45 



4 



5 

 ( )1-And 



30 



5 







i 



J : 



\ 

















5 



32 



5 



40 





10 

 01 



35 



7 



I 



h 





\ 



I 



little 



6 



31 



10 



18 



14 



10 



1 



35 



6 



2 



I 



I 



\ 



2 



\ 



