3«4 



the original shape of the granite boss rather than glacial 

 action. 



On the unnamed island just west of Queer island a trap 

 dyke of probable Keweenawan age cuts an agglomeratic 

 sericite schist. Specimens of this rock, showing the fine 

 grained porphyritic material near the edges and the coarse 

 diabase near the centre, are readily obtained, but it is 

 difficult to get good contact specimens. These latter 

 however may be secured on Slate island, where the same 

 dyke cuts the same type of country rock, and a contorted 

 metamorphosed zone about 30 feet (9 m.) wide is present. 

 This metamorphosed rock closely resembles the rocks 

 mapped as clay slate, etc., but the adjoining unaltered 

 rock is sericite schist and agglomerate containing an abun- 

 dance of carbonates. It is again seen at the contact of the 

 same dyke on Thompson island, though the adjoining 

 rock retains the ellipsoidal structure to a greater extent 

 than on Slate island. Leaving Thompson island the route 

 lies through the Keewatin channel to the north side of Rat 

 Portage bay (on mining location K. 85), where highly 

 altered Keewatin rocks mapped as clay slates, etc., are 

 well developed on the shore. These are principally horn- 

 blende and biotite schists, in some places containing an 

 abundance of garnets and intersected by large veins of 

 pyrrhotite. These rocks are principally developed near 

 the contact with the Laurentian granites. 



Bibliography. 



1, Lawson, A. C. The Geology of the Lake of the Woods 



region: Geol. Surv. Can., Ann. Rep. 



1885, Vol. I, Pt. CC. 

 2 The Geology of the Rainy Lake region, 



Geol. Sur. Can., Ann. Rep., 1887-8, 



Vol. Ill, Pt. F. 

 3. Coleman, A. P., Second report on the Gold Fields of 



Western Ontario: Ont. Bur. Mines, Vol. 



V, pp. 47-106. 

 4 Third report on the West Ontario gold 



region: Ont. Bur. Mines, Vol. VI, pp. 



71-124. 

 5 Fourth report on the West Ontario gold 



region: Ont. Bur. Mines, Vol. VII, pp. 



109-144. 



