PRE-CAMBRIAN CLASSIFICATION IN ONTARIO 599 



epochs, the Loganian, Animikean, and Timiskamian, but is of 

 economic importance only in the former two. Certain deposits 

 of titaniferous and non-titaniferous magnetites, not now being 

 worked, are associated with basic intrusives that appear to be of 

 pre-Algoman age. Arsenic occurs in two epochs and has been 

 produced in economic quantities from the rocks of both. In so 

 far as is known, gold occurs in economic quantity only in the 

 Algoman, although small quantities are obtained in refining the 

 copper-nickel ores, and certain auriferous quartz deposits, not now 

 productive, appear to be genetically connected with Keweenawan 

 intrusives. Nickel, as has been shown in the preceding table, 

 was deposited in economic quantities in two epochs. Cobalt, 

 silver, and copper are produced only from deposits of Keweenawan 

 age. Platinum, palladium, mercury, and other metals are found 

 in small quantities with Keweenawan ores. Zinc and lead have 

 been mined in the province, but the age relations of some of the 

 deposits are in doubt. 



RELATIVE ECONOMIC IMPORTANCE OF VARIOUS EPOCHS 



In Ontario in 19 13, the metal production from ore deposits of 

 various pre-Cambrian epochs was as follows: Keweenawan (silver, 

 copper, nickel, cobalt, arsenic), $36,559,688; Algoman (gold), 

 $4,543,690; Keewatin-Grenville (iron and iron ore), $1,195,150. 

 A comparatively small quantity of the nickel and copper credited 

 to the Keweenawan should be assigned to deposits that are asso- 

 ciated with basic eruptives of pre-Algoman, and probably post- 

 Timiskamian age, but the value is not definitely known. 



While at present in Ontario there is no production from deposits 

 of Animikean or Timiskamian age, millions of tons of iron ore are 

 mined from deposits of these epochs in the state of Michigan. 



It is to be understood that the ages given for the deposits do 

 not refer to secondary concentration, as, for instance, in the case 

 of iron ores, but to the epoch in which the metals were first 

 deposited. 



In a paper entitled " Metallogenetic Epochs in the Pre- 

 Cambrian of Ontario," presented before the Royal Society of 

 Canada, May, 191 5, the authors discuss more fully the age and 

 genetic relations of the ore deposits of the province. 



