NOTES ON A GRANITE CONTACT ZONE. — McINTOSH. 245 



until it crosses the Halifax and Southwestern railway and 

 turns north. The granite is an intrusive of probably Devon- 

 ian age. It evidently cooled and solidified under a great 

 thickness of pre-existing rock, which has since been largely 

 eroded. In the granite are found patches of darker, finer- 

 grained material, which is probably the remains of blocks of 

 the older rock partially assimilated. The effect of the high 

 temperature of the intrusive magma produced a marked 

 change in the overlying and surrounding rock masses. This 

 change consisted largely in the development of new minerals 

 out of some of the original constituents of the rock. As far 

 as surface observations go, for upwards of a mile from the 

 contact the influence of the heat was felt. A belt or zone of 

 metamorphosed rock thus surrounds the igneous mass. 

 Where the intruded rock varied in composition, the resultant 

 metamorhpism differed somewhat. Of this contact zone the 

 part more directly under discussion lies to the northwest of 

 Chocolate Lake. (See map). In the northern and eastern 



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