368 THE VEKMILION IKON-BEARING DISTRICT. 



Secondary minerals, such as sericite, chlorite, and hoi'nblende occur 

 abundantly in some of the rocks. The rocks have locally been crushed, 

 but the crushing has in no case reached such a degree as to produce schis- 

 tose rocks, although the microscope shows crushing effects reaching even to 

 the granulation of the quartz. The microscopic fractures are healed by 

 quartz and feldspar and also by hornblende when the fractures cross a horn- 

 blende individual. In su.ch a case one can readily distinguish the second- 

 ary needles of nearly colorless hornblende which traverse the fractures and 

 unite the pieces of the old massive green hornblende individual. 



RELATIONS TO ADJACENT FORMATIONS. 



Relations to the Lower Huronian. — The Cacaquabic granite lies adjacent 

 to the Lower Huronian sediments, which very nearly surround it. In the 

 area in which the sediments are wanting the gabbro lies next to the granite. 

 The relations of the granite to the adjacent formations are not nearly so 

 clear here as were the relations described for the Snowbank granite. The 

 granite contains dark-colored chloritic basic inclusions which may have 

 been brought up from the Archean greenstone that underlies the sediments, 

 an anticline of it lying a short distance southeast of the granite, and another 

 north of it. The Cacaquabic gi'anite grows finer grained as the mantle of 

 sediments is approached, and it has been foiuid, moreover, cutting the sedi- 

 ments in dikes which show clearly that it is intrusive in them and of 

 younger age. If it has metamorphosed them, as is probably the case, its 

 metamorphism is concealed by the later metamorphism caused by the gabbro. 



Relations to the gabbro. — The statement that the gabbro is later than the 

 granite is not warranted by any actual contacts that have been found 

 between them, or by the occurrence of any inclusions of the granite in the 

 gabbro, but is based chiefly on. their field relations, shown on the accom- 

 panying map, and on the comparatively youthful age of the gabbro. Thus 

 it will be seen that the granite everywhere, except on the southeastern 

 edge, is surrounded by the sediments. Presumably it was originally 

 completely surrounded by them; but for this narrow area,, however, the 

 gabbro has cut out the sediments and overlaps on the area underlain by 

 granite. 



