REPORT OF THE CHIEF ASTRONOMER 



527 



SESSIONAL PAPER No. 25a 



Analysis of Sumas granite. 



Si0 2 



Ti0 2 



ALA, 



Pe,O s 



FeO 



MnO 



MgO 



CaO 



BaO 



Na^O 



K 2 



H 2 at 110°C.. . 

 H,0 above 110°C. 



P=0 5 



CO, 



Sp. gr. 



The calculated norm is:- 



Quartz 



Orthoclase.. .. 



Albite 



Anorthite 



Corundum . . 

 Hyper sthene. . . 



Magnetite 



Ilmenite 



Apatite , 



Water and CO,. 



100-27 

 2-651 



Mol. 



71-24 1 



187 



•42 



005 



14-11 



138 



1-75 



011 



1-23 



017 



tr. 





1-07 



027 



2-87 



051 



•09 



001 



2-37 



038 



3-97 



042 



•11 





•59 





•17 



001 



•28 





34-86 



23-35 



19-91 



13-62 



•92 



2-83 



2-55 



•76 



•31 



•98 



100-09 



In the Norm classification the rock enters the sodipotassic subrang, riese- 

 nose, of the alkalicalcic rang, riesenase, in the persalane order, columbare; but 

 it is very close to amiatose, the corresponding subrang of the order britannare. 



In the older classification it is obviously a common type of biotite granite. 

 The specific gravities of two of the freshest specimens are 2-651 and 2-653. On 

 account of the alteration of the rock a iiseful determination of the actual 

 mineralogical composition by the Rosiwal method is practically impossible. The 

 mode is in this case not very different from the norm. 



Diorite. — The dioritic rock of the intrusion-breccia is also considerably 

 altered, as if by weathering. Its essential minerals are green hornblende and 

 plagioclase, averaging basic andesine. Orthoclase is an abundant accessory and 

 some interstitial quartz is always present. Much epidote with some chlorite and 

 kaolin are the secondary minerals. 



The smaller diorite xenoliths in the granite have been more or less com- 

 pletely recrystallized and modified in composition by the granitic magma. The 

 hornblende there characteristically occurs in long idiomorphic blades shot 

 through the feldspar and other constituents. In one thin section of a xenolith, 

 potash feldspar and quartz are so abundant as to cause the rock to simulate a 

 granodiorite ; in that case it seems probable that the original diorite has been 



