W. G. Foye — Nephelite Syenites of Ontario. 431 



the writer that the origin of these rocks was perhaps closely 

 associated with the origin of the nephelite syenites. Column 1 

 of Table I gives the composition of a typical amphibolite de- 

 rived from limestone. Column 2 is the analysis of an average 

 limestone from the same locality. 



SiO, 



Table I. 



1 

 50-00 



2 



2-27 



TiO 



0-82 





A1,0 3 



Fe 0, 



18-84 

 2-57 



1-31 



FeO 



MgO 



MnO 



CaO... 



NaO 



5-51 



4-63 



0-08 



10-65 



4-48 



3-20 



49-88 



KO 



... _ 1-18 





2 



CO 



o-io 



42-73 



s 



CI 



HO 



0-03 



o-io 



1-00 











99-97 99-39 



It will be seen that the limestone lost in the process of its 

 transformation to amphibolite 39 - 2 per cent of lime and 42-6 

 per cent of carbon dioxide. On the other hand, it gained 47*7 

 per cent of silica, 19 per cent of alumina, 6 - 8 per cent of iron 

 oxide, 1*4 per cent of magnesia, 45 per cent of soda, and 1*2 

 per cent of potash, beside other minor elements. 



Table II shows the added oxides and the same oxides from 

 the type canaditeof the Haliburton area (see page 418) recalcu- 

 lated to 100 per cent. 



Table II. 



1 2 



Amphibolite 



from Nephelite 



limestone syenite 



Si0 2 60-4 56-2 



A1 2 3 22-8 20-6 



Fe 2 3 &FeO 8-8 10-8 



MgO 1-7 0-5 



Na 5 5-0 7-6 



KO 1-3 4-3 



loo-o loo-o 



Am. Jour. Sci. — Fourth Series, Vol. XL, No. 238. —October, 1915. 



28 



