20 



Brought forward 94 '2 



Titanite I 



Epidote 3 



Chlorite 



Calcite 



Kaolin and Muscovite 



ioo -o 



This rock is more closely related to the diorites than 

 the granites, and might appropriately be called a quartz 

 diorite or tonalite. 



The basic bands included in the granodiorites are 

 made up mostly of dark micaceous and hornblendic schists 

 and fine grained gneisses. They are considered to repre- 

 sent unabsorbed, in places partially absorbed, portions of 

 the intruded rocks, but have been so intensely altered and 

 completely recrystallized that all traces of their original 

 character have disappeared. They often alternate with, or 

 are cut across by bands, of granodiorite, and in some 

 instances have a brecciated appearance due to the number 

 of granitic, aplitic, and pegmatitic dykes crossing them in 

 all directions. Near the basic areas, the granodiorites 

 are usually strongly and regularly banded, the dark bands 

 closely resembling varieties of the included schists. 



The basic schists dip at various angles, but in one 

 area are nearly horizontal. The direction of schistosity 

 conforms as a rule with that of the enclosing gneissic rocks. 



Aplitic and pegmatitic dykes occur everywhere cutting 

 both the granodiorities and the included schists, but are 

 especially abundant along the western margin of the range. 

 The pegmatite dykes are often of large size, and, as a rule, 

 are very coarsely crystalline. The ordinary constituents are 

 white orthoclase, light pink microcline, quartz, and dark 

 and white mica. Secondary garnets are occasionally pre- 

 sent. It is noteworthy that the acid dykes, although 

 belonging to the closing stages of the intrusion, are nowhere 

 schistose themselves. In the western portion of the range 

 they usually cut the schistose granodiorites almost at 

 right angles. 



Small basic dykes, younger than the aplites and peg- 

 matites, occur in the range, but are nowhere plentiful in the 

 Skeena section. The common varities are diabases and 

 hornblende lamprophyres. 



