REPORT OF THE CHIEF ASTRONOMER 447 



SESSIONAL PAPER No. 25a 



The darker bands have not been systematically examined with the micro- 

 scope but their field habit is that of common mica gneiss, often passing over 

 into feldspathic mica schist; they never seem to carry any hornblende. They 

 occupy probably no more than five per cent of the area covered by the Eastern 

 phase. 



These zones were regarded in the field as located along planes of maximum 

 shearing. They accord very faithfully in attitude with a strike of N. 2° to 25° 

 W. and a dip nearly vertical, but sometimes 75° or more to the east-riortheast — 

 structural elements induced by regional orogenic« movements in the Cordillera. 

 It is improbable that the banding represents peripheral schistosity about the 

 Cathedral batholith. The chief reason for excluding this view is that peripheral 

 schistosity is lacking in the great Similkameen batholith, which is also cut by 

 the Cathedral granite. It appears, on the other hand, that the Rem m el bath- 

 olith was already crushed and its banding produced before either the Simil- 

 kameen or Cathedral granite was intruded. 



Interpretations of the Two Phases. — Three interpretations of the two phases 

 are conceivable. They may be supposed to be distinct intrusions of two differ- 

 ent magmas; or, secondly, original local differentiation products in the one 

 batholith; or, thirdly, distinguished in their present compositions because of 

 the unequal dynamic metamorphism of a once homogeneous magma. Against 

 the first view is the fact that the two phases, where in contact, seem to pass 

 insensibly into each other. In favour of the third view are several facts which 

 do not square with the second hypothesis, and the writer has tentatively come to 

 the conclusion that the third hypothesis is the correct one. Among those facts- 

 are the following: 



1. The Eastern phase covers that part of the Remmel body which has 

 suffered the greatest amount of dynamic stresses exhibited either in the Remmel 

 or in any other of the larger components of the Okanagan composite batholith. 

 It has been seen that the less intense though still notable dynamic metamor- 

 phism of the Osoyoos granodiorite led to the special excretion of most or all 

 of the hornblende, apatite, magnetite, and titanite from that rock and the secre-" 

 tion of those leached-out compounds in the free spaces of the shear zones. The 

 biotite was similarly segregated, but its mobility was found to be considerably 

 less than that of the hornblende. If the metamorphism had been yet more 

 energetic in the Osoyoos body, the more soluble compounds would have been 

 carried away completely and the whole would have crystallized in the form of 

 acid biotitic gneiss banded with especially micaceous schists in the zones of 

 maximum shear. Such appears to the writer to be the best explanation of the 

 Eastern phase of the Remmel batholith. 



2. The composition of the rock and the fact that, as above mentioned, it 

 seems to have been thoroughly recrystallized into a strong, well knit, banded 

 gneiss without cataclastic structure agree with this view. 



3. The conclusion is substantiated in the study of more moderate shearing 

 in the "Western phase itself. There the strongly granulated and not reerystal- 



