434 



DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



Within the area covered by the Commission map (Figure 31), the present writer 

 has found no pyroxenite, but has referred all the massive intrusives of the 

 Chopaka pendant (excluding dikes) to two rock types and their metamorphic 

 derivatives. 



Most of the rock within the area is feldspathic and seems to belong to a- 

 fairly steady type — normal gabbro transitional to metagabbro. It is a dark 

 gray-green, medium-grained, hypidiomorphic-granular rock, originally composed 

 of essential labradorite (Ab x An x ) and diallage and accessory apatite, with a 

 little magnetite. Crush metamorphism, supplemented by ordinary weathering, 

 has largely changed the diallage into actinolitic amphibole, both compact and j 

 smaragditic. The specific gravity of the least altered rock is 2-959. 



V V V V V 



Figure 32. — Map showing relations of the Cathedral and Remmel batholiths and the 

 Ashnola gabbro. The Younger Phase of the Cathedral granite is shown by stippling. 

 The remarkably straight contact line of the Cathedral granite lies sensibly parallel to the 

 gneissic banding in the Remmel batholith, Eastern Phase. Scale : — 1 : 118,000. 



That common rock type is associated with a large body of a dark greenish- 

 gray, fine-grained rock of which several specimens show the composition very 

 clearly. It was originally made up entirely of granular olivine without any 

 certain accessory constituent. No trace of chromite has been found. Serpen- 

 tine, talc, tremolite, and magnetite are present in most of the thin sections, but 

 apparently in all cases as decomposition products of the olivine. The specific 

 gravity of the rock varies from 3-100 to 3-173. It is a dunite without chromite. 



The field relation of the gabbro and olivine rock has not been determined. 

 They may belong to distinct intrusions or they may be due to differentiation! 



