﻿Or... 



• 33-36 ' 



Ab;.. 



. 36.68 



An.... 



. 11. 12 



Co... 



. 1.85 



Qz... 



. 4.14J 



Hy.. 



. 5. OCT 



Mt... 



. 4.18 



Fl ... 



. 0.78 



Ap... 



• i-34. 



GEOLOGY OF THOUSAND ISLANDS REGION 1 83 



Norm of Alexandria syenite, analysis i : 



Class i, persalane 

 Order 5, Canadare 

 87.15 Rang 2, pulaskase 



Subrang 3, pulaskose 



11.30 



The rock itself contains considerable green horblende and biotite 

 which, together with the accessory magnetite, titanite, apatite and 

 pyrite, constitute about 15$ of the rock, (elsewhere they run up 

 to 25 or 30^, carrying the rock into the dosalane class) meaning 

 of course that some of the lime, alumina and potash calculated 

 with the salic minerals of the norm are in the hornblende and 

 biotite. Microcline, microperthite and oligoclase are all present in 

 some quantity, plagioclase being somewhat in excess. Some of the 

 microperthite is secondary after oligoclase. The rock has beautiful 

 cataclastic structure, showing much more crushing than the Picton 

 granite. Chemically it is seen to be very close to the green syenites 

 of similar silica percentage, the chief difference being in the higher 

 magnesia and in the relative proportions of ferric and ferrous 

 iron and of the alkalies. The higher magnesia expresses itself 

 mineralogically in the formation of hornblende and biotite, in- 

 stead of the pyroxenes of the green syenite. The general rock 

 is somewhat more basic, and with a higher percentage of f erro- 

 magnesian minerals than the normal green syenite. 



The augen gneiss of analysis 4 is a much more acid rock, a tosca- 

 nose, suggesting caution in attempting to account for it as a 

 phase of the syenite. The analysis is so close to that of the Picton 

 granite of the last column as to be almost grotesque. Quite cer- 

 tainly it has no relation whatever to the Picton granite, though 

 mimicing it so closely chemically. The green syenites of the region 

 show wide'r range of variation than that shown in this case, never- 

 theless the intrusion here is of such comparatively small size that 

 variation in composition to this amount would be quite unusual. 

 Hence the analyses rather tend to reinforce Smyth's conclusion 

 that we really have here two separate small intrusions, side by side. 



Mineralogically the augen gneiss consists of quartz, feldspars 

 and biotite, with accessory magnetite, titanite and apatite, and 



