NATURE OF BATHOLITHlC INTRUSIONS 



365 



density of the materials successively irrupted and crystallized is rigidly 

 followed. 



For a new reason, therefore, it is profitable to regard the many intru- 

 sive bodies as forming a single composite batliolith. Favoring that con- 

 cept, the chemical and physical nature of the unit masses, systematically 

 variable as these are, and the general geological structure of the Okanagan 

 Eange alike command attention. To the petrographical systematist the 

 inclusion of such rocks as peridotites and gabbros with nepheline syenites 

 and malignites may be like classifying bats with birds, but the geological 

 and even genetic connection of both alkaline and non-alkaline types is 

 here manifest. 



Nature of batholithic Intrusions 



REPLACEMENT THEORY AND ILLUSTRATION 



Year by }rear 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 Okan- 



+ '+ + *++;++•,+ + 



f fHHfiH! 

 + + + + + + + + + +. 



+ + + + • -f + + + + "+ jP5 

 +•++ + +■+. + ■++■ + 



+ * + f +,+ +'*■ -h + 

 + + ++ + + + + + + + 



-f + + + + + + + + + -H 

 + + + + + + + + + + + 



Figure 8. — Contact Surface between the Castle Peak Cranodiorite and tilted Cretaceous 



Sandstones and Argillites. 



The section is shown in the wall of a glacial cirque at the eastern end of the stocky the 

 point marked "A" in figure 7. Scale, 1 inch to 175 feet. 



agan Composite batholith repeatedly illustrates this truth. The writer 

 is frankly unable to conceive that the huge Cathedral batholith, for ex- 

 ample, could have been formed by any process of simple injection without 

 leaving abundant traces of prodigious rending and general disorder in the 



