258 THE VERMILION IRON-BEAKING DISTRICT. 



GRANITES OF TROUT, BURNTSIDE, AND BASSWOOD LAKES. 



DISTRIBUTION, EXPOSURES, AND TOPOGRAPHY. 



Distribution. — The rocks described under the above heading occur 

 along the northern edge of the VermiHon district, and extend from Vermihon 

 Lake on the west to the east side of Basswood Lake on the east, where they 

 cross the international boundary. Observations made on Hunters Island, 

 Province of Ontario, Canada, show that similar rocks are present in that 

 province and that they possess the same geographic and geologic relation- 

 ship to the members of the Kaministiquia iron range, which is the continua- 

 tion of the Vermilion iron range of Minnesota to the northeast, as do their 

 Minnesota analogues to the various members of the Vermilion iron range of 

 Minnesota. They are for this reason presumed to belong geologically with 

 the granite of Basswood Lake. While it is known that the granites of 

 Trout, Burntside, and Basswood lakes extend at least as far northeast- 

 southwest as the limits of the area mapped, these granites — or granite 

 closely related to them — are presumed to have a very much greater areal 

 extent, as upon the Canadian maps granites are shown covering large areas 

 in portions of Ontaiio which are continuous with the Vermilion range. 

 The Minnesota and Canadian maps and a traverse made by canoe show 

 that granite extends a considerable distance north of the international 

 boundary. Since the prime object of the survey whose results are here 

 described was to study the Vermilion district from an economic point of 

 view, no attempt has been made to- study the outlying granite more closely 

 than was requisite to determine its relations to the rocks of the district. 

 Moreover, observations have been confined almost altogether to a very 

 narrow area bordering the main mass of granite. The traverses usually 

 ended as soon as we were sure that the limits of' the granite had been 

 passed. 



Exposures. — The exposures are, as a rule, very numerous, and the line 

 of contact between the main granite area and the area of the Vermilion 

 range proper is usually marked by a topographic break of some kind. 

 Either a valley and stream are present or else a lake or chain of lakes lies 

 along the contact. In either case as soon as the depression is crossed, if 

 one comes from the south, for instance, the granite exposures usually begin, 

 and they continue in great number as far north as we have been. 



