PERRTTGINOUS YKINS IN THE NOIITHEEN COMPLEX. 187 



known l()c;ility at which these rocks are found is in the northern i)art 

 of the city of Marquette, a short distance west of Light-House Point. The 

 largest masses of the feiTugiuous rocks are seen on Michigan street, from 

 which ])hxce they extend east and west for some distance. At ilicliigau 

 street the rocks are separated into two parts 1>a- a Liver of green schist. A 

 short distance to the east but a single mass is found, and this, as it is followed 

 farther east, becomes mucli smaller. It finally disappeai's at the end of one 

 outcrop sejDarated from others by an interval of 10 feet. The feiTuoinous 

 rocks at this place have a strike and dip closely corresponding with those 

 of the foliation of the schists with which they are associated, biat when 

 examined minutely the two are found to be discordant. 



East of this 2^1ace, t)n the neck of Light-House Point, various 

 narrow seams of iron-bearing rock, from a fiew inches to a foot wide, are 

 found. These ai-e interlaminated with the green schist of tlie point. One 

 of them can be traced for a distance of 100 feet or more, while the other 

 smaller ones disappear witliiu a short distance. Some of these narrow 

 masses have become soft and liydrated, and such resemble the ferruginous 

 material taken out from the Eureka mine 2 or 3 miles to the west. The 

 Eureka ore is a soft hematite in the green schist. 



The belt of green schists from the Eureka mine to Light-House Point, 

 in common with the entire green-schist area, shows evidence of extensive 

 dynamic action, the rocks all having- a schistosity, and in some places being 

 broken up into lozenge-shaped blocks, between which solutions might 

 readily pass. It is believed that all of the ferruginous deposits of this area, 

 in their banding, in their relations to the surrounding green schists, in tlieir 

 great vai-iability in thickness, and in tlie rapidity with which tliev die out, 

 coiTespond in every respect to infiltrated veins, and are, therefore, secondary 

 to the countrv rock. 



In sec. 2, T. 48 X., R. 27 W., just north of the old Ilolyoke mine, 

 outside of the area mapped, there are also found within the green schist of 

 the Northern Complex various masses of sideritic slate, ferruginous slate, 

 ferruginous chert, and griinerite-magnetite-schist. In tlieir relations t() the 

 surrounding rocks they in all respects resemble those adjacent to Marcpiette.^ 



'In one of the Archean islands, in sec. 2.3, T. 47 N., R. 26 W^., are also found narrow veins of 

 jasper, the widest l>eing less than a foot thick. 



