104 THE ROYAL SOCIETY OF CANADA 



Sturgeon Lake. Turning northward from Seine river, gold has 

 been found in many veins in the rocks around the shores of Sturgeon 

 Lake. The veins are of quartz with calcite and siderite, carrying free 

 gold, pyrite, chalcopyrite, sphalerite and galena. The rocks of the 

 area are schistose and massive greenstones, representing altered dia- 

 base or andésite, quartz porphyries and coarse porphyrites, often 

 with large phenocrysts of plagioclase, all of which are typical of the 

 Keewatin complex throughout central Canada. Intimately mixed 

 with these are some small areas of sedimentary graywacke and dolo- 

 mite, which may possibly represent the Temiskamian in this district. 

 These rocks are intruded by the Sturgeon Lake granite and associated 

 porphyries which Dr. Moore^ considers to be newer than the Laurentian 

 and which are therefore probably of Algoman age. At the St. Anthony 

 mine the main vein is close to the contact between the schist and gray- 

 wacke and the granite which has been intruded into them, the north 

 end of the vein being wholly in the granite, and the south end wholly 

 in the schist and graywacke. 



On the Barnard Claim the veins occur at the contact of green- 

 stone (Keewatin) and quartz-porphyry, which is regarded by Dr. 

 Moore as a phase of the Sturgeon Lake granite. The veins occur not 

 only on the contact itself, but they run out into both rocks. Speaking 

 of the quartz stringers in the quartz porphyry Dr. Moore writes that 

 they suggest "that the fissures had been developed at the time of cool- 

 ing and contraction of this rock." 



Everywhere throughout the Sturgeon Lake District the gold-bear- 

 ing veins are more or less closely associated with the occurrence of 

 quartz-porphyries or feldspar poiphyrites. Such porphyries may be 

 both of Laurentian and Algoman ages, though the latter are the ones 

 genetically connected with the gold veins. 



Michipicoten District. In the Michipicoten District, which lies 

 North-east of Lake Superior, gold-bearing veins occur in the Pre- 

 Cambrian rocks over a very considerable area. 



The veins are composed chiefly of quartz, though the quartz is 

 often associated with a large amount of Ankerite. They usually 

 exhibit a streaked or banded appearance, with irregular lighter and 

 darker bands, the lighter bands being of fairly pure quartz, while the 

 colour of the darker bands is usually accounted for by the presence of 

 chlorite or tourmaline. In one place the quartz was darkened by the 

 presence of molybdenite or graphite. Pyrite and pyrrhotite are the 

 principal metallic minerals present, but these are not so abundant in 

 the veins carrying quantities of ankerite, as in those in which this latter 



1 E. S. Moore. The Sturgeon Lake Goldfield. 20th Ann. Rep. Ont. Bur. Min. 

 1911. p. 138. 



