434 THE PENOKEE IRON BEARING SERIES. 



been found, tlie l)t'lt always being luirntw, so that the amount of iron iu 

 the carbonate present was insufficient when concentrated to form large ore 

 bodies. 



The srreenstone-conolomerate area ^•aries from a material Avhich is a 

 basic eruptive amygxlaloidal flow, through various volcanic or seraivolcanic 

 elastics, to rocks which are wholly water-dei)osited. 



North and east of the greenstone-conglomerate is a continuous \^•ide 

 belt of fragmental rocks, which extends nearly to Gogebic lake. The i-ocks 

 south of this belt vary in their character, being in the western part a- por- 

 phyrite of such a nature as to indicate that it is a surface flow; through the 

 central \r<irt of the area, greenstone-conglomerate, and in the eastern part of 

 the area, the gneisses and granites of the Southern Complex. North of the 

 belt are the eruptives of the Keweenaw series. At one place, just west of 

 Gogebic lake, the Eastern sandstone is the overlying rock. It seems prol)- 

 able that this l»elt of fragmentals is the equivalent of the northern part of 

 the Iron-bearing m(Mnl)er with perhaps the lower part of the Upper slate 

 member to the westward. If it extends farther east than Gogebic lake, it 

 probably passes under tlie Eastern sandstone. 



The rocks of this licit are very largely clay-slates which have an 

 apparent southern dij). In places, however, they become strongly ferrugi- 

 nous, when a northern dip is usually found. The latter are believed to 

 represent true liedding and the southern dips to lie secondary cleavage 

 induced l)v pressure. The rocks have a wide variation in lithological 

 character, running from those which are purely fragmental to those which 

 are purely nonfragmental sediments. The phases intermediate between these 

 two exti-emes are those most abundant. The fragmentals are very much 

 like those north of the iron-bearing belt in the main area. The mingled 

 nonfragmental materials are the various oxides of iron, siderite, and chert. 

 The rocks, then, vary from those which lithologically belong to the Iron- 

 bearing membei- to those which are tyjiical of the Upper slate. The iron 

 varies in its coml)inntion from an oxide in tlie western part of the area to 

 a siderite in tlie eastern part. This is another case in whicli the widespread 

 occurrence of iron <ixide is due to tlie alteration of a ferriferous carl>onate. 

 The basal portion at several places in the eastern part of the belt are 



