352 R. A. DALY — THE OKAKAGAtt COMPOSITE BATHOLITH 



uncrushed Cathedral and Similkameen batholiths and the Kruger body 

 also suggest that all three belong to one eruptive epoch of several stages — 

 an epoch long subsequent to the intrusion of the Osoyoos and Eemmel 

 batholiths. The Similkameen granite is clearly intrusive into the Kruger 

 alkalines, which may owe their strained and often granulated condition to 

 the forceful entrance of that immense and immediately adjoining body of 

 granite (see figure 3). 



Three complete chemical analyses of types from the body have been 

 made, which clearly show that the rare family of malignites is here repre- 

 sented on a large scale. The analyses are not given or discussed in this 

 paper, as their details are scarcely relevant to the main purposes of the 

 geological inquiry. 



SIMILKAMEEN GRANITE BATHOLITH 



General character and mineral constituents. — The staple rock of the 

 Similkameen batholith is a medium to coarse grained, light pinkish-gray 

 soda granite. Its essential constituents are hornblende, biotite, quartz, 

 basic oligoclase (averaging Ab 7 An 3 ), and the alkaline feldspars, micro- 

 perthite, microcline, microcline-microperthite, and orthoclase. The last 

 named is characteristically rare; microperthite is the most abundant of 

 the alkaline feldspars. The accessories are magnetite, apatite, and beau- 

 tifully crystallized titanite. Allanite is a rare accessory ; epidote is occa- 

 sionally present, but apparently is secondary. The structure and order 

 of crystallization are normal for granites, though microperthite is often in 

 phenocrystic development. A determination of the weight percentages of 

 the constituents found in a type specimen collected in the Similkameen 

 River valley was made by the Rosiwal method. It gave : 



Per cent 



Oligoclase 29.8 



Microperthite 27.0 



Quartz 22.0 



Orthoclase and microcline 0.7 



Biotite 5.5 



Hornblende , 4.2 



Magnetite , . . . , 1 .8 



Titanite 1.1 



Epidote 1.1 



Apatite 8 



100.0 



This calculation is rough, though it gives a calculated specific gravity 

 for the rock (2.682) that checks well with the observed specific gravity 

 (2.693). 



