19-t B. A. Daly — Secondary Origin of Certain Granites. 



average gabbro from the many sills of the Boundary belt. A 

 comparison of cols. 2, 4 and 7, Table II, shows that col. 4 

 corresponds to a rock-type intermediate between the two types 

 actually analyzed. It is planned that a rather complete set of 

 total analyses of the various phases of the Moyie sill will be 

 published in the final report of the Chief Commissioner for 

 Canada on Boundary Surveys. 



Partially absorbed inclusions of the quartzite occur also in 

 the upper, granitic zone of the intrusive. 



Next to the peculiar granite-gran ophy re is a hundred-foot 

 (thick) zone of intermediate rock which, with rapid transition, 



js; 



Fig. 3. Photograph of specimens showing contrast of color between a 

 basic and a normal phase of the gabbro of the British Columbia sills and 

 between both of these and two phases of the Moyie Sill granophyre-granite 

 shown on the left. 



replaces the acid rock as the section is thus carried inwards 

 through the sill. The mineralogical composition of this inter- 

 mediate rock is shown in Tables I and II. 



The structure is again hypidiomorphic-granular with con- 

 tinual gradations into the granophyric. The grain varies from 

 medium to rather coarse. 



The intermediate rock grades imperceptibly into the normal 

 gabbro of the internal part of the great intrusive body. 



The variation in mineral composition among the zones of 

 granite, intermediate rock and gabbro are shown in Table II. 



