THE IRON BEARING MEMBER. 273 



therefore, the strike of the dike, if the iron rocks were turned back to a 

 horizontal })osition, vvouhl be east and west. At the IVnce mine tlie strike 

 of the Iro'n-bearino- rocks is about 25° north (if east, wliih^ tlie dike in the 

 mine has an eastern comixincnt of 35°. The (hke would, then, if the Iron- 

 bearing rocks were turncil to a liorizoiital j»osition, strike about east (iU° 

 nortli. It is for the present assumed that the dikes cut throiitili the iron 

 formation before their uplifting. If this is the ca.se, it would follow that, 

 upon the average, the dip of the dikes was !I0°, that is, they were per- 

 pendicular to the strata through whicli they came, and that the strike of 

 the dikes varied iVoiii east and west to east (iO^ north. Tiie average strike 

 of the larger nunii)er of dikes would be about northeast and southwest. 



'i'he thickness of tlie.se dikes varies gieath', rumnng from a few 

 inches to nearly !)() feet. In most of the mines in which the deposits 

 of ore are of any consideralde size, the main dikes are generally 

 six or more feet in thickness, while it is noticeable that genei'ally the 

 larger mines have thick dikes, although in the same mines tliere are 

 often one or more smaller dikes. The main (_'olbv dike is nearly 1)0 

 feet thick; tlie main Noirie dike, 35 feet thick. The onl\ ore de])osit 

 west of Sunday lake, the development of whicli lias found no <l\ke, is the 

 main Ironton-Federal bodv. This ore bodv pitches to the east, just as is 

 later seen of the dejiosits associated with dikes. It is possible that when the 

 workings of these mines penetrate deeper thev will come in contact with a 

 dike; one is known to come to the surface 300 or 400 feet west. As to 

 the mines east of Sunday lake, it has already been note(l that their cliarac- 

 ter is (juite exceptifmai, and they may for the present l)e excluded from this 

 discu.ssion. 



From the eastern jiitcli of the dikes, with reference to' the rocks of the 

 iron formation, it is .evident that they nuist, if the\' continue in tlu'ir 

 observed directions, come to the surface to the west of the workinj^s of each 

 of the nunes in which they are foinid. As the present workings are. in 

 most ca.ses, Imt a few hundred feet deep, it follows that, when these pitches 

 are high, the dikes would reach tlie surface but a short distance from the 

 ore ilejiosits. It thus l)ecomes probable that there are as many dikes in the 

 lower horizons of the Iron-l)earing member as are seeu in all of the difi'er- 

 MON XIX 18 



