128 R. BELL NICKEL AND COPPER DEPOSFIS OF SUDBURY. 



In the district under consideration the main line of the Canadian Pacific 

 railway crosses, almost at right angles, the narrowest part of the Huronian 

 belt proper, which has here a width of only about twenty-four miles. The 

 strike is therefore northeast and southwest, and in this pinched portion of 

 the trough the rocks on the opposite sides dip at high angles toward the 

 center. Sudbury Junction is situated southeast of the center of the trough, 

 and from it the Sault Ste. Marie branch of the railway runs upon the gen- 

 eral strike of the Huronion rocks throughout almost its entire length. At 

 thirty-three miles northwest of Sudbury Junction, or near Geneva lake, the 

 main line enters upon an outlying basin of stratified Huronian rocks meas- 

 uring eight miles in width on the railway by seventeen in length from north- 

 east to southwest, and having a long point running Avestward into the town- 

 ship of Craig. This, for convenience, may be called the Geneva lake outlier. 

 At the southern extremity of Onaping lake, a few miles to the north of this 

 outlier, there is a smaller one, measuring only three miles in width by four 

 in length. 



The various members of the Huronian system in the Sudbury district are 

 of much interest in connection with questions relating to metamorphism and 

 the origin of crystalline rocks, and also as illustrations of the general char- 

 acter of the system in this part of Canada. They consist principally of gray- 

 wackes and quartzites, various forms of diorites, quartz-diorites and horn- 

 blende schists, mica schists, diabases, argillaceous sandstones, black and 

 drab clay slates, together with volcanic breccias, in addition to the gneiss 

 and quartz-syenite already referred to. 



The rocks which occur in greatest quantity in the stratified Huronian belt 

 between lakes Huron and Wahnapit^e, and which constitute the lowest 

 members of the series, are quartzose graywackes and quartzites, with occa- 

 sionally a little felsite. Thick bands of quartzites, mostly very light in 

 color and standing at high angles, form the conspicuous range of La Cloche 

 mountains overlooking Lake Huron and the long narrow points projecting 

 into that lake between Spanish river and Killarney. The fact that this 

 great local development of quartzites happens to occur at the most accessible 

 part of our principal Huronian belt has given rise to the erroneous notion 

 that the Huronian rocks of Canada in general consist mostly of these rocks. 

 The quartzites of the region about La Cloche appear to belong to three or 

 four belts which double around in a synclinal form, and are thus repeated 

 within comparatively narrow limits. Quartzite constitutes the principal 

 rock all around Lake Panache and along the lower parts of Vermilion and 

 Spanish rivers, but further to the northeastward, or in the contracted part 

 of the belt of the Sudbury district, the corresponding rocks, with a greatly 

 diminished volume, are much mixed with felspathic and argillaceous matter, 

 constituting massive graywackes ; while still further on, or in the country 



