REPORT OF TEE CHIEF ASTRONOMER 463 



SESSIONAL PAPER No. 25a 



Table XXIX. 



Showing chemical relation of Similkameen and Cathedral haiholiths. 



— 



1 



2 



3 



4 



SiO„ 



47-76 



6B55 



71 



41 



71-21 



TiO„ 



220 



•40 





00 



16 



A1 2 3 



18-58 



16 21 



15 



65 



15 38 



Fe 2 3 



2.19 



1-98 



1 



92 



•25 



FeO 



9-39 



180 





00 



147 



MnO 



•29 



12 





07 



06 



MgO 



415 



132 





61 



■33 



CaO 



939 

 03 

 •02 



3 86 

 •01 

 •03 



2 



47 

 00 

 04 



137 



SrO 



None. 



BaO 



•09 



Na.O 



361 

 "47 



4 07 



2-84 



4 

 3 



19 

 44 



4-28 



K 2 



4 85 



H 2 0- 



12 

 ■53 



•78 



01 

 •24 

 15 





00 

 16 

 00 

 04 



•02 



ELO+ 



43 



P„0 5 



05 



















99 51 



99 59 



100 00 



99 95 



1. Analysis of Ashnola gabbro. 



2. Analysis of Similkameen granodiorite. 



3. Result of subtracting one-fifth part of each oxide shown in Col. 1 from the amount of the 

 corresponding oxide in Col. 2, and recalculating to 100 per cent. 



4. Analysis of Cathedral granite. 



The divergence of the oxide proportions in the calculated residue from 

 those in the Cathedral granite is inconsiderable except in the case of potash 

 and lime and even those differences are no greater than those often observed in 

 two analyses from any one batholith in other regions. It may fairly be claimed 

 that the gravitative separation of non-silicic and subsilicic constituents (gab- 

 broid mixture) making up about one-fifth by weight of the Similkameen grano- 

 diorite, would leave, in the upper part of the magma-chamber, a more silicious 

 magma quite like that of the Cathedral granite. The composition of the less 

 dense residue would be the same whether the separation took place through 

 fractional crystallization or through true magmatic splitting. 



Obviously, little stress can be laid on the actual figures resulting from the 

 calculation just described. It has rather been intended as offering a concrete 

 illustration of the hypothesis. On the other hand, the general principles under- 

 lying the hypothesis are, in the writer's belief, worthy of attention, for they 

 seem to be among the most promising among all the principles of modern 

 petrology.- The calculation sbows that it is not unreasonable to retain the con- 

 ception that the Cathedral granite is a gravitative differentiate from the Simil- 

 kameen granodiorite magma, and that a magma allied to gabbro or diabase and 

 thus matching the basaltic and other dikes actually cutting the Cathedral 



