Coleman — Nepheline and other Syenites in Ontario. 147 



Art. XYIII. — JVepheline and other Syenites near Port Cold- 

 well^ Ontario ; by A. P. Coleman. 



A FEW years ago some very interesting dikes of a rock con- 

 taining analcite named "heronite" or analcite tingiiaite were 

 described by the writer from the north shore of Lake Superior 

 between Heron Bay and Peninsula on the Canadian Pacific 

 railway;^ and the opinion was expressed that nepheline 

 rocks should be found connected with them somewhere in the 

 region. Dr. Adams also has suggested the same idea, basing 

 his belief on some rock specimens from the region of Peninsula 

 in the Geological Survey collection. They are augite syenites 

 of an nnusual kind often associated with nepheline syenites. f 



In connection with an excursion to the iron range of the 

 Slate Islands an opportunity was taken to examine the railway 

 and shore near Port Coldwell, and it was intended to visit Pic 

 Island a few miles off shore, where Professor Pirsson and others 

 have suggested that nepheline rocks would probably be found, 

 but unfortunately no suitable boat could be got at that little 

 harbor, and this had to be given up. 



No syenites of any kind were found between Heron Bay 

 and a point three miles east of Peninsula, where augite syenite 

 had been obtained a few years before ; but west of Peninsula, 

 more than half way to Port Coldwell, considerable stretches of 

 nepheline syenite were discovered. So far as the study of the 

 specimens has gone one can say that a great area of syenites 

 and associated rocks rich in alkalies, derivatives of a magma 

 differentiated into a whole series of related species, like those 

 so elaborately described by Brogger in the Christiania region 

 of IN^orway, occurs in this region. 



The first rock of the group, going west, is the dark augite 

 syenite which commences three miles east of Peninsula, and 

 with some interruptions of red syenite and more basic rocks 

 extends to a long trestle at mile 818, a distance of nine or ten 

 miles, with an unknown width. From the trestle west to a 

 catting beyond Peninsula, the prevalent rock is a gray or 

 purplish gray nepheline syenite, having an extent of about four 

 miles. It is probable that detailed mapping of this little 

 explored region would show large areas of this syenitic group 

 of rocks, including Pic Island, and it is hoped that in the 

 future these interesting eruptives may be studied more at 

 length. 



The only previous references to this group of syenites are to 



* Bureau Mines, Ontario, 1899, pp. 172-174; and 1900, pp. 186-191. 

 f Jour. Geol., vol. viii, No. 4, pp. 322-325. 



