VKRMILIOK DISTRICT OF MINNESOTA 9 



The second paper was by the same author. 



VERMILION DISTRICT OF MINNESOTA 

 BY .1. MORGAN CLEMENTS 



[Abstradl 



The Vermilion district occurs in northeastern Minnesota, extending from Ver- 

 milion lake north 70 degrees east to Gunflint lake, on the international bonndary. 

 As described, the district is about 80 miles long by 4 to 10 miles in width. The 

 area surveyed comprises nearly 1,000 square miles. The stratigraphic succession 

 is as follows, given in descending order: 



Pleistocene Glacial drift. 



Keweenawan Great gabbro and Logan sills. 



(Unconformity.) 



Upper Huronian (Animikie series), confined to r- Upper slate formation, 

 east end of district (Gunflint formation (iron-bearing formation). 



(Unconformity.) 



flntrusives. 



I Knife slates. 



Lower Hnronian <^ ^ -,-r ..... 



Lower Huronian iron-bearing formation. 



[Ogishke conglomerate. 

 (Unconformity.) 



f Intrusive granites, porphyries, and greenstones. 



. , ,-, .,. • V ! Soudan formation (the iron-bearing formation). 



Archean (\ermilion series) ■{ „, ^ ,,• -j ,, j u • 



I Ely greenstone, an ellipsoidally parted basic 



I igneous and largely volcanic i-ock. 



The structure is complex. The Vermilion district is broadly a great complex 

 synclinorium bounded on the north by the Archean granite and on the south by 

 Huronian granite, Keweenawan gabbro, with the Upper Huronian slates coming 

 in for a short distance. The ores are high grade hematites occurring in structural 

 basins. First, the iron comes froui preexisting rocks, and it is deposite4 to form 

 the sedimentary iron-bearing formations. In the case of the Archean Soudan iron- 

 bearing formation the iron comes from the Archean greenstone (basic and inter- 

 mediate intrusives and volcanics). Second, after the folding the iron is leached 

 from the iron-bearing formation chiefly, and after being carried down by descend- 

 ing meteoric waters is precipitated as the oxide in places favorable for its accumu- 

 lation, thus forming the ore deposits. 



The paper was illustrated by lantern slides. Remarks were made b}^ 

 C. Pv..Van Hise and U. S. Grant. 



The following paper was presented : 



PACIFIC MOUNTAIN SYSTEM IN BRITISH COLUMBIA AND ALASKA 

 BY ARTHUR C. SPENCER 



Remarks were made by B. K. Emerson. The paper is printed in this 

 volume. 



II— TUnj, Gkoi,. 8or. Am,, Vol. 14, 19U2 



