[harvie] palaeozoic breccia of the vicinity op MONTREAL 267 



photographs 9 and 10.) The heat of the intrusive has baked the adjacent 

 limestone so that it is now much more compact and also lighter in colour. 

 'A section from the unaltered limestone to the intrusive shows this 

 baking increasing with approach to the igneous rock, furthermore the 

 limestone is increasingly shattered till a point is reached at which the 

 fragments drop off into the fused material where they form the bulk of 

 the inclusions. In this process of shattering by which the action of 

 stoping went forward, every gradation is visible, from the solid unaltered 

 limestone to the fragments finally frayed off and held in suspension in 

 the breccia. The circulation of the materials of the intrusive has evi- 

 dently been very vigorous since fragments of other rocks, granites, etc., 

 are found carried up to the top of the stope within one foot of the un- 

 shattered limestone. The magma has not exerted any pronounced 

 solvent action on the inclusions, either the basic limestones or the more 

 acid granites; neither has the heat greatly affected the limestone, which 

 one would expect to find in the crystalline state. 



The breccia showing in the west wall (slide No. 1), extends across 

 the road passing in front of the quarry. It is cut by the two dykes shown 

 in figure 11. The larger is two feet wide and nearly vertical. In cross- 

 ing the quarry, it is found to split into about fifteen "smaller dykes and 

 these cut the breccia dyke in the rear wall near the top of the face. 

 Examination under the microscope shows this dyke to be a variety of 

 camptonite. The second dyke is eight inches thick and dips to the south- 

 east at an angle of 35°. It cuts the masses of breccia in the west wall 

 and northwest corner, also the vertical dyke just mentioned. It is con- 

 tinued in the northeast wall where it was seen to include several frag- 

 ments of a dark coloured rock like essexite. In the upper portion the 

 dyke is much decayed to a brownish granular earth; undecomposed 

 material suitable for a section was, however, obtained near the bottom. 

 This also is a camptonite. 



The breccia in the northwest corner is much decomposed, but ap- 

 pears to consist of two phases, — the first (slide No. 6), having numerous 

 inclusions in a fine grained paste is found as a border phase; the second 

 (slide No. 23), is largely coarse grained igneous material with few frag- 

 ments, apparently the pure paste forming the interior of the mass. The 

 breccia is cut by a vertical dyke four feet wide which is found in the 

 bottom of the quarry. This dyke can be traced for over nine chains to 

 the northwest, being five feet wide where it crosses Summit Avenue. 

 It belongs to the bostonite group. 



The breccia dyke in the rear wall of the quarry is connected with 

 the patch in the north corner. Little can be seen of the relations of the 

 breccia except in the small section exposed by the quarry. The only 



