DIORITE INTRUSIONS IN GRAYWACKES AND QUARTZITES. 129 



east of Lake Wahnapitse, they have passed almost entirely into pure argil- 

 lites, which are there very extensively developed. To the north of Lake 

 Wahnapitse the quartzites reappear in great force. On the opposite or north- 

 western side of the Sudbury trough this series is represented by a thick 

 band of gray quartzite, which appears to be always characterized by scattered 

 pebbles of white quartz, but it is insignificant in volume compared with the 

 quartzites and gray wackes along the southeastern side of the trough. 



In the gray wacke and quartzite area of the region under consideration the 

 crystalline diorites occur as numerous intruded masses, varying from half a 

 mile to ten miles in length. They are of various forms, but their greatest 

 diameters are approximately parallel with the strike. The rock is generally 

 of a dark or sea-geen color and moderately finely crystalline. Three or four 

 of these masses occur around Lake Panache and nine or ten to the north- 

 east, between this lake and the Canadian Pacific railway line, and seven 

 more beyond that part of the railway between Sudbury and Wahnapitse 

 river. About a dozen small diorite areas have been found in the quartzite 

 and argillite region around Lake Wahnapitae. Besides these massive dio- 

 rites, bands of obscurely stratified varieties of the same rocks, of quartz- 

 diorite and of dioritic and hornblendic schists are sometimes associated with 

 the quartzites and graywackes in the townships of McKim and Denison, in 

 the Geneva lake outlier, along Spanish river and around Lake Wahnapitse. 

 A beautiful and very coarsely crystalline hornblende rock occurs near the 

 Dominion, the Stobie, and the McCounell mines and in a few other localities. 



Bands of compact brown-weathering dolomite, generally whitish and dove- 

 colored, occur locally in the graywacke and quartzite series. They are found 

 in considerable volume on different parts of Lake Panache, and they occur 

 also near Lake Huron in the township of Rutherford, on La Cloche lake, 

 on Wahnapitse river, on Geneva lake, and near Cartier station. Similar 

 dolomite is occasionally found as patches in the finer-grained syenite or 

 altered graywacke. 



Two long and remarkable intrusions of diorite of a gray color and having 

 a coarser texture than those already described are found cutting the gneiss 

 and quartz-syenite areas of this region. They are each about a mile wide 

 in the middle. Both run northeast and southwest, or parallel to the general 

 strike of the stratified portions of the Huronian rocks nearest to them, and 

 diminish to narrow points at the extremities. The first of these commences 

 at Whitson lake, in the township of Blezard, and runs southwestward into 

 Denison, a distance of twenty-four miles, while the second has been traced from 

 the northeastern part of Levack for about eighteen miles southwestward. 

 Most of the heavier deposits of nickeliferous ore, so far discovered, are asso- 

 ciated with these two diorite belts, and they will be again referred to in this 

 connection. A smaller dioritic intrusion, apparently of the same class as 



