REPORT OF THE CHIEF ASTRONOMER 455 



SESSIONAL PAPER No. 25a 



The average specific gravity of thirteen fresh specimens of the Kruger bodv 

 is 2-750. 



Metamorphism. — Few of the specimens collected are free from signs of 

 crushing. This has sometimes induced a decided gneissic structure, and almost 

 always the microscope shows fracture and granulation. The abundant develop- 

 ment of metamorphic melanite and biotite and perhaps also the occasional pro- 

 duction of large poikilitic scapolites indicate ' some recrystallization through 

 dynamic metamorphism. The abundance of microcline and the corresponding 

 subordinate character of the orthoclase is another, yet more familar, relation 

 brought about through the crushing. The mechanical alteration of these rocks 

 is far from being as thorough as in the case of the Osoyoos batholith. This is a 

 principal reason for believing that the alkaline mass was intruded after the 

 Osoyoos granodiorite had been itself well crushed. No other definite field evidence 

 for or against that view has been discovered. However, the magmatic relationships 

 between the 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 batho- 

 liths. 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 28). 



Similkameen Batholith. 



General Character. — The staple rock of the Similkameen batholith (Plate 

 40) is a medium- to coarse-grained, light pinkish-gray soda granite. Its 

 essential constituents are hornblende, biotite, quartz, basic oligoclase (averaging 

 Ab 7 Arij), and the alkaline feldspars, microperthite, microcline, microcline- 

 microperthite, and orthoclase. The last named is characteristically rare; micro- 

 perthite is the most abundant of the alkaline feldspars. The accessories are 

 magnetite, apatite, and beautifully crystallized titanite. Allanite is a rare 

 accessory; epidote is occasionally present, but apparently is secondary. The 

 structure and order of crystallization are normal for granites, though micro- 

 perthite is often in phenocrystic development. 



A type specimen collected on the wagon-road following the west side of the 

 Similkameen river valley, at a point three miles north of the Boundary slash, 

 was studied microscopically and chemically. 



A total analysis of this specimen (No. 1355) was made by Mr. Connor, 

 with result as follows : — 



