476 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



the Cathedral granite and the Basic Complex. These dikes represent essentially 

 the same common basic type which forms the Ashnola gabbro and other of the 

 oldest intrusives of the range. As the phitonic energies became exhausted in 

 the formation of the Cathedral granite, the original heat-carrier has alone 

 survived in the molten state and is capable of injection on the small, dike scale. 

 In this feature the history of the composite batholith is similar to that of many 

 other batholithic provinces, where the latest granite is diked by common basalt 

 or by its hypabyssal, chemical equivalent. 



Finally, it will be noted that the conditions of crystallization underwent a 

 decided change during the long interval between the intrusion of the Osoyoos- 

 Remmel granodiorite and the Kruger alkaline body. Magmatic stages la to 8b 

 inclusive, afforded non-alkaline rocks rich in hornblende and carrying plagio- 

 clase, either basic or of medium acidity, as the dominant feldspar. These bodies 

 may be regarded as belonging to one consanguineous series. Magmatic stages 

 A to 7 inclusive, afforded alkaline rocks bearing nephelite in the most basic 

 phases and microperthite (orthoclase in 6b and 7) as the dominant feldspar 

 throughout the series except in certain basified contact-zones. This group 

 belongs to a second consanguineous series. The youngest of all the intrusives, 

 the basalt and andesite dikes, belong to a third consanguineous series, closely 

 allied in mineralogical and chemical composition with the earlier members 

 of the first series. The first and third series each began with a magmatic type 

 which is chemically equivalent to the commonest of extrusive lavas (basalt). 

 The second series began with a basic magma which may have been a peculiar 

 differentiate of the same original basaltic couch e or, as seems more probable, 

 of that couche locally modified and controlled in its differentiation by some 

 absorption of sedimentary terranes into which the Kruger body was injected. 



METHOD OF INTRUSION. 



Year by year the conviction has been growing ever stronger in the minds 

 of many able geologists that such a batholith as any one of those here described 

 has assumed its present size and position by actually replacing an equal or 

 approximately equal mass of the older, solid rock. The Okanagan composite 

 batholith repeatedly illustrates this truth. The writer is unable to conceive 

 that the huge Cathedral batholith, for example, could have been formed by any 

 process of simple injection, without leaving abundant traces of prodigious rend- 

 ing and general disorder in the granites alongside. We have seen, on the 

 contrary, that the Similkameen granite on the east is notably free from such 

 records of orogenic turmoil, while the shear zones of the Remmel batholith on 

 the west most probably antedate the Cathedral granite intrusion. The very 

 scale of these great bodies is suggestive of bodily replacement; it is hard to 

 visualize an earth's crust which would so part as to permit of the laccolithic or 

 chonolithic injection of a mass as great as a batholith. 



The problem will be discussed at length in chapter XXVI., in which the 

 many facts won from the study of the Boundary section will be correlated with 

 ihe essential facts of the field in other parts of the world. 



