REPORT OF THE CHIEF ASTRONOMER , 443 



SESSIONAL- PAPER No. 25a 



granodiorite because of the loss in heavy constituents (specific gravity, 2-692). 

 A further stage of granulation and energetic . shearing led to the formation of 

 perfect schistosity in rock made up of the quartz-feldspar ruins of the original 

 rock, cemented by very abundant biotite and epidote — the biotite-epidote gneiss 

 (specific gravity, 2-783). The fissures and fluid-filled cavities developed in the 

 zones of maximum shear are now occupied by the strongly schistose hornblende 

 gneiss (specific gravity, 2-939) and similar products of complete solution, 

 migration, and subsequent complete recrystallization. 



The granodiorite has thus become not only mechanically crushed, but to a 

 large extent rendered heterogeneous. It is now not only gneissic, but banded 

 in zones of new rock markedly varied in composition. The schistosity and 

 banding everywhere agree in attitude; the strike varies from N. 10° W. to N. 

 75° W., but over large areas, as indeed over the whole batholith east and 

 west of Osoyoos lake, averages N. 45° W. almost exactly. Neglecting minor 

 crumplings, the dip varied from 70° N.E. to 90°, averaging about 82° N.E. 

 This average attitude is close to that observed in the schists cut by the grano- 

 diorite, but represents an exceptional strike among the main structural axes of 

 the Cordillera. It may be noted that shearing is much more manifest on the 

 «ast side of Osoyoos lake than on the west side. 



Eemmel Batholith. 



From the Pasayten river to the western base of Cathedral Peak the larger 

 part of the Boundary belt is underlain by the Remmel batholith. This granitic 

 body is like the Osoyoos batholith in exhibiting a well- developed gneissic and 

 banded structure, along with a great heterogeneity in chemical and mineralogical 

 composition. The causes of this variable constitution are here again two in 

 number. The one is original or magmatic; the other is secondary and due to 

 metamorphism. The metamorphic action has been most marked in a band 

 immediately adjoining the Cathedral batholith. This part, comprising one- 

 seventh of the total area in the Boundary belt, is called the Eastern phase. The 

 rest of the body as exposed in the belt is called the Western phase. Each phase 

 is variable in itself but the two are contrasted by general characteristics which 

 persist throughout most of each area. At the Pasayten river the batholith is 

 unconformably overlain by the Lower Cretaceous Pasayten series of strata. 



Western Phase. — The least metamorphosed part of the batholith is to be 

 found in the Western phase. None of the collected specimens can, however, be 

 confidently regarded as illustrating the precise average of this phase or of the 

 batholith as a whole. The writer has, however, selected for analysis one fresh 

 specimen which approximates the probable average rock of the Western phase 

 a3 originally constituted. The specimen was taken from a ledge two miles south 

 of the Boundary line and 2,000 yards from the contact with the Ashnola 

 gabbro. 



This rock has the look of a medium- to coarse-grained, slightly porphyritic, 

 gray granite. Lustrous black biotites in conspicuous, often quite idiomorphic 



