THE LOWER HURONIAN. 357 



connected in the field directly with the granite dikes which cut the gray 

 Embarrass granite," lying a number of miles to the south, but their general 

 characters are so similar that they are presumed to be of the same age as 

 these dikes, and to have been derived from the same source. Moreover, 

 farther east practically the same granite is found in dikes which are clearly 

 ofFshoots from the Giants Range granite, and those at the extreme western 

 side of the district are likewise supposed to be offshoots connected under- 

 ground with the Griants Range granite mass, although at the surface they 

 are a good many miles distant from it. The metamorphosing effect of the 

 Griants Range granite on these sediments has been described under the 

 description of the sediments themselves (pp. 340-341). 



As we go northeast in the district beyond White Iron Lake, especially 

 along the Kawishiwi River, we find a comparatively small area of sediments, 

 conglomerates, graywackes, and associated slates extending from near the 

 mouth of the Kawishiwi River on Farm Lake, sec. 34, T. 63 N., R. 11 W., 

 eastward into sec. 29, T. 63 N., R. 10 W. The area underlain by these 

 sediments has a north-south extent from the Kawishiwi River to Clear- 

 water Lake of about 1^- miles. These rocks are identical petrographically 

 with the rocks which have been classed with the Lower Huronian sediments 

 and are presumed to be of the same age. They are cut through and 

 through by dikes of the Giants Range granite, and as a result of this 

 intimate intrusion they have been metamorpliosed to their present condition 

 of mica- and hornblende-schists and gneisses. 



Relations to the gabbro. — Within the limits of the map (PL II) the 

 Giants Range granite and the great Keweenawan gabbro are in proximity 

 to each other only along the Kawishiwi River, from sec. 34, T. 63 N., R. 

 10 W., to sec. 19, T. 63 N., R. 9 W. Although the area lying within the map 

 in which the granite and gabbro lie close together is small, nevertheless the 

 relations between the two rocks are sufficiently clear. The gabbro lies 

 obliquely across the northeastern continuation of the Giants Range g-ranite 

 and even overlaps the Archean greenstones and the Lower Huronian 

 sediments, which lie north of the granite. The way in which these rocks are 

 interrupted in their eastern continuation indicates an eruj)tive relationship 

 of the gabbro to them. Moreover that this is the true relationship between 



«The Mesabi iron-bearing district of Minnesota, by 0. K. Leith: Mon. U. S. Geol. Survey Vol. 

 XLIII, 1903, p. 186. 



