306 THE VERMILION IRON-BEAflING DISTRICT. 



tlie Ogislike cong-lomerate and, as in the preceding cases, the conglomerate 

 is found to be penetrated by offshoots from this granite massive. At other 

 places in the district, where the conglomerate is distant from the granite 

 massive, it is cut by dikes of rhyolite-porphyries or granite-porphyries, or 

 possibly of both. In all cases, however, the relationship is clearly that of 

 intrusion, the conglomerates being intruded and metamorphosed by the 

 granites. Hence the conclusion that the conglomerates are of greater age 

 than the granites which penetrate them. 



Relations to certain basic and intermediate dikes of Lower Huroniaii age. — 

 At numerous places dikes of slightly varying character — altered basalts 

 and lamprophyres — have been found cutting the Lower Huronian rocks. 

 None of these dike rocks are found as dikes in the overlying Upper 

 Huronian series. Hence they are believed to have been intruded in the 

 Lower Huronian rocks at about the time when they were being folded and 

 intruded by the aforementioned granites. Certainly some of the dikes are 

 later than some of the granites, as they are found cutting the granites. 



RELATIONS TO THE UPPER HURONIAN .SERIES. 



It was found that the most difficult problem of relation to be solved 

 was that of the relationship between those rocks which are here classed as 

 the Lower Huronian (consisting of the Ogishke conglomerate, the Agawa 

 formation, and the Knife Lake slates) and the Upper Huronian (Animikie) 

 rocks. These rocks come closest together in the vicinity of Gobbemichi- 

 gamma Lake, and here, if at all, their relations were to be determined. 

 A considerable time was therefore spent in the study of the rocks in this 

 vicinity. Unfortunately where the rocks of the series come closest together 

 the Lower Huronian is represented by conglomerates which give no good 

 strikes and dips, and the Animikie is represented by the metamorphosed 

 iron formation which lies at its base in this district. 



In the area referred to the Lower Huronian rocks are extremely folded, 

 and where this series is in contact with the Animikie, the vertical or very 

 steeply dipping rocks of the Lower Huronian were found to strike in such 

 a direction on the east side of Gobbemichigamma Lake as to bring them 

 very nearly at right angles against the Animikie, which has a very low dip 

 to the south, with a strike slightly, north of east. Only in two places 

 were the Ogishke conglomerate of the Lower Huronian and the iron- 

 bearing formation of the Upper Huronian series observed in contact, and 



