REPORT OF THE CHIEF ASTRONOMER 437 



SESSIONAL PAPER No. 25a 



granite, which now, as illustrated on full three miles of contact line, projects 

 strongly into the body of the Complex. A large block of the latter formation, 

 measuring about 400 yards in length by 200 yards in width, was found within 

 the Park granite mass itself; it may represent a roof -pendant in the stock, and 

 thus a small analogue to the larger basic body in its relation to the Eemmel 

 batholith. 



The Basic Complex is made up of a remarkable assemblage of basic plutonic 

 rocks of at least three different periods of intrusion. The oldest types are 

 coarse-grained. They include highly irregular bodies of hornblendite, which in 

 the field is often seen to be transitional into a labradorite-bearing homblende- 

 augite peridotite; this in its turn merges into hornblende-augite gabbro. All of 

 these rocks are believed to be of contemporary origin. Their occurrence is so- 

 sporadic that it is difficult to say how much of the whole basic area they really 

 cover — possibly one-quarter of it by rough estimate. These rocks are cut by 

 many large dikes and more irregular masses of hornblende-gabbro, augite-horn- 

 blende gabbro, and hornblende-biotite-quartz gabbro. Such types are of medium 

 to coarse grain. Their specific gravity varies from 2-873 to 2-986. 



As there is no discoverable system in the differentiation of the earliest 

 intrusive members, varying as they do most capriciously from ledge to ledge, so 

 there is no discoverable system in the trends or occurrence of the coimtless later 

 injections of the gabbros. The complication has been still further increased by 

 the intrusion of thousands of narrow and broader dikes of granite. Much of 

 the granite is apophysal or aplitic from the Remmel batholith; some of it is 

 apophysal from the magma supplying the Park granite stock, while many dikes 

 of acid pegmatite locally traverse the whole mass. The complication was finally 

 made perfect through the enormous crushing which the Basic Complex iinder- 

 went, both during the intrusion of the granites and during the orogenic revolu- 

 tion when the Eemmel granodiorite itself was sheared into banded gneisses. 



In the shearing of the Basic Complex its material was metamorphosed and, 

 in part, it migrated. The mode of migration is believed to be that which will be 

 briefly discussed in connection with the petrographic descriptions of the crushed 

 Osoyoos and Bemmel batholiths. The metamorphism has developed many schis- 

 tose phases, among which hornblende-biotite-diorite gneiss (specific gravity, 

 2-766 to 2-863) and well foliated hornblendite are common. 



As a result of this long and varied history, scarcely any two ledges within 

 the area of the Complex accord in composition. The constitution of what 

 appears to be the commonest phase of the Complex, the augite-hornblende gabbro, 

 and the peculiar fawn colour of its feldspar, furnish a probable correlation of 

 part of the whole mass with the Ashnola gabbro. There is no certainty of similar 

 correlation with the basic rocks of Mount Chopaka. 



Nodule-bearing Peridoiiie Dike. — The Complex is cut by a remarkable forty- 

 foot dike which is excellently well exposed on the north slope of Park moun- 

 tain. The exact locality is found on the divide west of the Ashnola river, about 

 1,500 yards southeast of the Line monument and on the 7,'250-foot contour. The 

 dike is sensibly vertical and strikes east-southeast. Its wall-rocks are typical 



