REPORT OF THE CHIEF ASTRONOMER 



493 



SESSIONAL PAPER No. 25a 



figures and text illustrating this stock in the preliminary paper will be fully 

 reproduced in the present chapter. 



Finally, the stock merits attention as it throws light on the problem of the 

 age of the petrographically similar Similkameen batholith and therewith aids 

 in discovering the difficult geological chronology of the whole Okanagan com- 

 posite batholith. 



Dominant Phase. — The staple rock of the Castle Peak body is a fresh, light 

 gray, granitic type of medium grain. In the ledge the mass of dominant 

 quartz and feldspar is speckled with fairly abundant, lustrous-black hornblende 

 and biotite. Under the microscope the principal feldspar is seen to be 

 plagioclase, often zoned and averaging andesine, Ab 3 An 2 . Orthoclase, probably 

 sodiferous, is a less abundant essential. The hornblende is deep green and is 

 sensibly identical with that of the Similkameen granite. A few of the horn- 

 blende crystals contain small cores of augite or of felted uralite apparently 

 derived from augite. No free pyroxene is present. Magnetite or ilmenite, 

 apatite and titanite are the accessories. 



A typical fresh specimen (No. 1441), collected on the southwest spur of 

 Mt.- Frosty, has been analyzed by Mr. Connor, with result shown in Table 



xxxn, Coi. i. 



Table XXXII. 



Analyses of the Castle Peak and Similkameen granodiorites. 



SiO, 



Tio; 



ALA 



Fe-A : . 



Feb.' 



MnO 



MrO 



CaO 



SrO 



BaO 



Na,0 



KA 



H,0 at 105°C. . 

 H 2 above 105°C. 

 PA 



1. Mol. 



2. 



66-55 1 



109 



66.55 



•60 



008 



•40 



15-79 



155 



16-21 



•15 



001 



1-98 



3-08 



043 



1-80 



•06 



001 



•12 



2-14 



053 



1-32 



3-47 



062 



3-86 



•01 





•01 



•03 





•03 



4-39 



•071 



4-07 



2-80 



030 



2-84 



•05 





•01 



•40 





•24 



•04 





•15 



Sp.gr 



The calculated norm is: 

 Quartz. 



99-56 



2-678 



Orthoclase. 

 Albite.. .. 



Anorthite.. . 

 Hyper sthene. 

 Diopside. . . . 

 Ilmenite. . . . 

 Magnetite. . . 

 Water 



99-59 

 2-693 



18-24 



16-68 



37-20 



15-01 



9-02 



1-71 



1-21 



•23 



•45 



99-75 



