Section IV., 1915 [24i] Trans. R.S.C. 



Métallo genetic Epochs in the Pre- Cambrian of Ontario. 



By WiLLET G. Miller, F. R.S.C, and Cyril W. Knight. 

 (Read May Meeting, 1915.) 



A few years ago Waldemar Lindgren in an instructive paper 

 gave what he called "an epitome of the principal epochs of the segre- 

 gation of metals over our continent.^" He showed that North 

 American "metalliferous deposits have been formed [at various 

 epochs] since the earliest times of geological history." The deposits 

 are grouped by him under the headings pre-Cambrian, Palaeozoic, and 

 so forth. 



In describing the pre-Cambrian deposits, Lindgren said: "The 

 pre-Cambrian period embraces a very long time and many differing 

 epochs of ore formation; but for our present purposes it will be 

 necessary to consider it as a whole." 



During the last decade, owing to the great progress that has been 

 made in the production of metals in Ontario, special facilities have 

 been provided for the study of pre-Cambrian rocks. Our information 

 has been much increased concerning the age relations of the rocks 

 that represent various epochs of this great period, and the ore deposits 

 that are associated with them. It has seemed to the authors that it 

 might now be of interest to present a more detailed classification, 

 than that of Lindgren, of the pre-Cambrian ore deposits of the Prov- 

 ince, showing the various metallogenetic epochs into which the period 

 may be divided. In no other part of the continent, or of the world, 

 has the pre-Cambrian proved to be of greater economic interest, 

 and in no other country are these rocks known to be represented 

 by more important metallogenetic epochs. The variety of metals 

 produced here is greater than elsewhere. The Province has not only 

 the world's greatest deposits of nickel, among which have been de- 

 veloped mines that compare favorably in economic importance with 

 those of any other metals found elsewhere, but the gold mines and 

 the cobalt-silver areas are also recognized as being among the greatest 

 of the world. 



From the following table it will be seen that there have been 

 at least four great metallogenetic epochs during the pre-Cambrian 

 period in Ontario — Grenville, Algoman, Animikean and Keweenawan. 

 A fifth epoch of minor importance should probably be added to repre- 



ijour. Can. Mining Inst., 1909, pp. 102-113. 



