108 THE ROYAL SOCIETY OF CANADA 



The character of the gold-bearing veins of the Porcupine district 

 has been described in detail by Mr. A. G. Burrows^ and need not 

 be repeated here, father than to draw attention to the mineials 

 associated with the gold, namely Pyrite, Pyrrhotite, and occasionally 

 Arsenopyrite, and gangue minerals such as Scheelite, Tourmaline, 

 and Feldspar (plagioclase ?) , and to the conclusion that the veins 

 were formed at considerable depth. 



The rocks in which the quartz veins occur are greenstones and 

 greenstone schists, quartz- and feldspar-porphyries, and quartzites 

 of the Iron Formation, all of Keewatin age; conglomerates and gray- 

 wacke of Temiskamian age; and quartz-porphyries and granites be- 

 longing to the Pre-Cambrian Complex but of uncertain age. 



In the vicinity of the Hollinger Mine the greenstones and quartz- 

 porphyries have been folded, sheared and altered by lateral pressure, 

 and at a subsequent period, when the direction of pressure had changed 

 to some extent, veins were formed as a number of lenses en echelon, 

 in a series of overlapping fissures, the individual lenses running with 

 the foliation of the schist, while the whole vein system varies from it 

 at an angle of 10° to 20°. On the Hollinger property the oblique 

 pressure would appear to have caused the various layers of the schist 

 to slide on each other, and in places to separate, producing channels 

 for the circulation of mineral-bearing solutions, while on some other 

 properties the layers of rock broke under the pressure, and gave rise 

 to faults in and near which the gold-bearing solutions were able to 

 circulate. 



The majority of the veins occur in the green schist, although as a 

 rule they are within a short distance of the schistose porphyry. 



Gold occurs not only in the quartz veins themselves, but in the 

 rock of the adjoining country for some distance on both sides of the 

 veins, almost invariably associated with pyrite, the two minerals hav- 

 ing replaced portions of the wall rock. 



In the vicinity of the Dome Mine, Temiskamian slates and con- 

 glomerates occur closely folded in with the greenstones, schists, and 

 porphyries of Keewatin age, and th*^ gold-bearing veins occur in the 

 conglomerates as well as in the greenstones and schists. The veins 

 were evidently formed after the conglomerate had been subjected to the 

 diastrophic forces which reduced it to its present condition, for they 

 have not participated to any material extent in the deformation. At 

 the same time there is no evidence to indicate that the veins in the con- 

 glomerate are different in age from those in the greenstone, so that 

 they may all be considered as post-Temiskamian or Algoman in age. 



1 A. G. Burrows. The Porcupine Gold Area. 21st Report Ont. Bur Min. 1912, 

 pp. 205-249. 



