[ADAMS A BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 1» 



them. The occurrences in question are the nepheline syenites of the 

 Sivamaiai series of India ^ and that of the Island of Alno - in Sweden. 

 A similar association has been noted in the occurrences at Kussa in the 

 Ural Mountains^ and in the nepheline rocks of the Kaiserstuhl in 

 Baden.* 



Concerning the calcite in the Indian occurrences, Holland says : — 

 '' ^'he caJcite occurs in granular crystals with apparently as much right 

 as any of the others to be considered a primary constituent. The crys- 

 tals form isolated granules, and there are no signs of secondary decom- 

 position the low silica percentage in this group of rock removes 



the chief theoretical difficulty to its crystallization from a molten magma 

 as u normal constituent of an igneous rock.'* The Alno rock contains 

 large masses of crystalline limestone as well as scattered granules of 

 calcite and micropegmatitic intergrowths of calcite with nepheline, 

 aegerine or feldspar, and Hoghom believes that the limestone has been 

 fused in the magma without decomposition and was, during the process 

 of solidification, crystallized out of the magma in precisely the same way 

 as the other minerals. In neither of these cases does limestone now oc- 

 cur in the immediate vicinity of the syenite, but it may, especially in 

 the latter case, have sunk down into it from overlying beds, since re- 

 moved by erosion. 



This is also considered by Graeff to be the true explanation of the 

 origin of the limestone inclusions in the Kaiserstuhl occurrence. Of 

 the crystalline limestone associated with the Kussa nepheline syenite, 

 Arzruni says that its " austreten unaufgeklart geblieben ist." 



^ Holland, T. H. — The Sivamaiai Series of Elseolite Sytnite and Corundum 

 Syenites in the Coimbatore District, Madras Presidency— Mem. Geol. Survey 

 of India, Vol. XXX— part 3, 1901, p. 197. 



^ Hogbom, A. G.— Ueber das Nephelinsyenitgebiet auf der Insel Alno^ 



Geol. Foren i. Stockholm Forh. Bd, 17. Heft 2. 1S95, s. 118. Also Abstract in 



Min. Mag. Vol. XI. (1897), p. 350, and Rosenbusch Mikr. Phys. (1896), pp. 

 169 and 171. 



•Arzruni, A. — Die Mineralgruben bei Kussa and Miass — (In the Livret — 

 Guide for the Ural Excursion of the International Congress of Geologists, St. 

 Petersburg Meeting, 1900.) 



*Graeff, — Zur Géologie des Kaiserstuhlgebriges — Mitt, der Bad. Geol. 

 Landesanst. Bd. II, 1892. 



Knop, — Der Kaiserstuhl im Breisgau — Leipzig, 1892; also Hogbom, A. G. 

 (loc. cit.) 



