REPORT OF THE CHIEF ASTRONOMER 267 



SESSIONAL PAPER No. 25a 



just south, of Summit creek. There belt E has already passed into the collar 

 of contact metamorphism belonging to the Bayonne batholith. On the Dewdney 

 trail all trace of the normal spangled schist is lost and the rocks which appear 

 to represent it are relatively very coarse-grained, crinkled muscovite-biotite 

 schist, alternating with micaceous quartzite. So complete is the recrystalliza- 

 tion that it has proved impossible to separate the contact-metamorphosed part 

 of belt E from the similarly altered schists of belt G. For this reason belt E 

 is, in the map, represented as ending in an arbitrary line drawn to indicate 

 the northernmost limit of the schist which actually shows the spangling with 

 biotite. From near the Kootenay river flat to a point four miles up Summit 

 creek, the coarse, glittering mica schists with their quartzitic intercalations 

 represent the utmost crystallinity and a very striking parallel to typical mica 

 schists in the great pre-Cambrian field of eastern Canada. This spectacular 

 exomorphic collar is more than two miles wide as measured outward from the 

 Bayonne granite. Within the collar the schists are powerfully crumpled and 

 the strike of both schistosity and bedding has been forced around so as to be 

 sensibly parallel to the contact-line of the Bayonne granite. The dip averaged 

 about 75° to the north but is quite variable. 



Petrography of Belt F. — East of the zone of spangled schist good outcrops 

 are specially rare for several miles. These sections were run across belt F but, 

 on account of the heavy forest cover, the information was but meagre. The 

 net result of these traverses went to show that the zone is, like belt D, com- 

 posed of sheared quartzite with subordinate interbeds of mica schist. The 

 quartzite is here usually much more schistose than that in belt D and is chiefly 

 a true quartz schist. Sericite or well developed muscovite, biotite, and chlorite, 

 all in minute foils giving by reflexion point-like scintles of light from the planes 

 of schistosity, are the micaceous minerals formed by the dynamic metamorph- 

 ism. The intercalated mica schists are much like those of belts A to D, but 

 almost never show the biotite spangles characteristic of the rocks of belt E. 

 In both the quartz schists and the mica schists there is, close to the Rykert 

 granite, an increase in the size of the mica foils and usually some development 

 of reddish garnets. These features are regarded as due to special contact- 

 metamorphism. A band of garnet-bearing amphibolite, 125 feet wide, and 

 apparently following the bedding-planes of the schistose quartzite near the 

 Rykert granite, is another example of greatly metamorphosed basic intrusives 

 in the Priest River terrane. 



Peripheral schistosity was developed in the belt by the Rykert granite 

 intrusion. On the north slope of Boundary creek near the contact, the strike 

 of bedding and schistosity was observed to run from [N". 25° E. to N. 45° E., 

 with dips varying from 30° to 45° N. W. 



On the top of the ridge and a mile from the contact the average strike is 

 about K 30° W. and the dip varies from 75° E. N. E. to 75° W. S. W. Farther 

 west the dip is northerly and flattens to 20° or less. Toward the western limit 

 of belt F, on the same ridge, the strike is about N. 25° E. and the dip nearly 

 vertical. In all these cases the strike and dip refer to the banding of the 



