OEE DEPOSITS OP UPPER HURONIAN. 



177 



87°. The severe deformation is clearly shown by the plication of the beds, 

 and by faults whose extent can not be determined, but which are accom- 

 panied by rather extensive reibiing-sbreccias. The breccias are cemented 

 b}' iron oxide. 



THE AMASA AREA. 



The Amasa deposits must of necessity be very briefly described, as I 



have been unable to obtain much information concerning the relations of 



the rocks as shown in the closed mine. In the early days of the mine it 



was thought by the 



mine captain that the 



volcauics formed the 



foot wall of the ore, 



and on his authority 



Van Hise says, "The 



ore of the Hemlock 



mine rests upon a 



stratum consisting of 



surface volcanic mate- 

 rial 1 ''■*■ Fig. 11. — Profile section illustratiDg results of diamond-drill TTork. 



Probably this is a mistake, for the section from west to east (fig. 11), 

 i. e., from the higher to the lower beds, obtained in two drill holes, is as 

 follows : 



Feet. 



Gray sericitic slate, discolored by iron 115 



Chert and jasper 59 



Pyritiferous black slate and quartzite 180 



Ore i'ormatioii 30 J 



Magnetitic slate 42 



Mottled slates, red and green, containing iron. Drilling ceased after passing through 70 



The thickness of the beds given is the true one and not the thickness 

 passed through by the drill, which cut through the beds at an angle. These 

 beds projected to the surface are found to be immediately underlain by 

 greenstone, in some places massive, in others tufaceous. Moreover, an 

 identical section is shown by a drill hole 4 miles southeast of Amasa, in sec. 

 26, T. 44 N., K 33 W. It was carried deeper, however, and after passing 

 through the mottled slate was bottomed in gTeenstone. From these diill 



'The iron ores of the .Marquette district uf Michigan, by C. K. Van Hise: Am. Jour. Sci., vol. 

 43, 1892, p. 130. 



MON XXXVI 12 



