DIABASE AND GRANOPHYRE OF THE GOWGANDA 

 LAKE DISTRICT, ONTARIO 



NORMAN L. BOWEN 

 Massachusetts Institute of Technology 



INTRODUCTION 



The rich silver deposits of Nipissing and Temiskaming districts 

 of Ontario are believed to be genetically connected with intrusive 

 diabases. Chiefly on this account, these diabases have received con- 

 siderable attention from many Canadian geologists. 



During the summer of 1909 special opportunity for studying these 

 rocks was afforded by the Ontario Bureau of Mines, to the writer, 

 while working in the vicinity of Gowganda Lake. 



The results of this study form the basis of this paper. 



GENERAL GEOLOGIC RELATIONS 



A brief resume of the geologic history of the Gowganda district^ 

 will be given in order that general relationships may be well under- 

 stood. 



The oldest rocks consist of a complex of chloritic and hornblendic 

 schists (altered basic volcanics), cut by quartz porphyries; together 

 with a minor quantity of jasper-iron formation and its associated 

 schists. This schist series (Keewatin) was subjected to intense 

 folding and its schistose character induced before the intrusion of the 

 great granite batholiths which in numerous places in the area are 

 seen cutting the series. This complex (Archaean) suffered a long 

 period of erosion before the deposition of the sedimentary series 

 now lying upon it. The lower series is made up of conglomerates, 

 quartzites, and slates of varying thickness. This in turn suffered 

 erosion, but apparently little disturbance, before the deposition of the 

 conglomerate-arkose-quartzite series lying upon it. These series 

 have been called Lower and Middle Huronian respectively. Into 



^ See also forthcoming report and map by A. G. Burrows, Ontario Bureau of 

 Mines, 191 o. 



658 



