23 



camptonite and essexite. The camptonites are the prin- 

 cipal dykes of the area. They are composed chiefly of 

 hornblende, biotite, feldspar, magnetite, some pyrite, 

 very little apatite and secondary calcite. 



RELATIVE AGES OF CHIEF TYPES. 



According to Brgoger, the rocks of the Norwegian sye- 

 nite area were derived from a common magma basin, 

 through a succession of irruptions beginning with the basic 

 rocks and forming a continuous series to the most acid 

 granites. He also states his belief that the later basic 

 dykes found cutting the main rock mass represent the final 

 depletion of the original magma basin. According to 

 Kerr, the oldest rocks of the Port Coldwell complex are the 

 basic picrites, olivine gabbros and essexites; while as in 

 Norway, the youngest rocks of the region are the narrow 

 basic dykes, camptonites, etc. Next in order of age to the 

 oldest basic intrusives are the augite syenite or laurivikite, 

 the red hornblende syenite, and the nepheline syenite. 



The difficulties of assigning a definite succession, for the 

 whole area can be understood only by those who have 

 made the attempt in other districts. To the writer of this 

 account, which is an epitomized statement of Kerr's con- 

 clusions, it seems that the general succession proceeding 

 from the oldest to the youngest was as follows : — ■ 

 i. Picrite, olivine gabbro and essexite. 



2. Augite syenite or laurivikite. 



3. Nepheline syenite. 



4. Red hornblende syenite 



5. Quartz syenite. 



6. Camptonites, etc. 



These syenites are all intrusive into the greenstones and 

 greenstone schists of the Keewatin and, so far as can be 

 judged, merge without any sharp line of delineation into 

 granites usually classified as Laurentian. 



BIBLIOGRAPHY. 



1. Logan, Sir Wm. E. Report of Progress, Geol. Survey of 



Canada, 1846-47. pp. 29-30. 



2 Geology of Canada, 1863, pp. 80-81, 



480, 647. 



