Relations of 1 the; Rocks. 



Keewatin Series. 



As the legend on the map shows, the oldest series known 

 in the region is called the Keewatin. It consists for the 

 greater part of basic volcanic rocks, now represented by 

 schists and greenstones, together with more acid varieties 

 such as quartz-porphyry. Associated with the Keewatin is 

 considerable sedimentary material, consisting of schistose 

 greywacke, jaspilyte, or iron formation, and crystalline lime- 

 stone, which is, however, not seen in large exposures in any 

 of the three mining areas. These sedimentary rocks are 

 believed to represent the Grenville series of southeastern 

 Ontario. 



Laurentian Granite and Gneiss. 



The rocks next younger than the Keewatin are grey gran- 

 ite and gneiss. They are well exposed along the railway 

 north of North Bay, and are called Laurentian. 



Temiskaming Series. 



After the intrusion of the Laurentian into the Keewatin, 

 there was a prolonged period of erosion, during which a 

 thick series of sediments consisting of conglomerate, grey- 

 wacke and other rocks was deposited. To this series in the 

 Cobalt and Porcupine areas the name Temiskaming has 

 been given. It is known in other areas to the north, south 

 and west of Cobalt and appears to be represented at 

 Sudbury by what Dr. Coleman has called the Sudbury 



series. 



Lorrain Granite. 



After the deposition of the Temiskaming sediments an 

 intrusion of granite, characteristically pink in color, took 

 place. This granite, which occupies large areas, is known 

 as Lorrain. The relations of this granite to both the older 

 and younger rocks are clearly shown at Cobalt. The granite 

 which gave rise to the gold deposits at Porcupine appears 

 to be of the same age. 



