A PYRRHOTITIC PERIDOTITE 137 



strated, but the possibility of their existence can hardly be ques- 

 tioned in view of the known occurrence of igneous rocks as rich in 

 sulphides as the one here described. That this rock is itself a dif- 

 ferentiation from a less basic magma is shown by the occurrence 

 about one-quarter mile northeast of the Millers farm of a much less 

 basic rock belonging apparently to the same intrusion but contain- 

 ing relatively small amounts of pyrrhotite. The original characters 

 of this rock are obscured by intense weathering, which has reduced 

 the rock to an irregular aggregate of pale -green chlorite, pale -green 

 or brown amphibole, much of it fibrous, and calcite. 



Sulphide-bearing rocks of the type here described are, however, 

 even more suggestive in their bearing on workable ore deposits when 

 we take into account the possibilities of local sulphide enrichment by 

 aqueous or pneumatolytic action. There is no evidence of such 

 enrichment at the- locality near East Union, nor do the rocks of the 

 surrounding region contain ore veins of any kind. It is evident, 

 however, that such processes acting upon a rock of this type would 

 be fully capable of producing ore deposists of a commercial character. 



Adams,' Coleman,^ and Barlow^ of the Canadian Geological 

 Survey have all attributed the primary concentration in the copper, 

 nickel, and cobalt ores of the Sudbury district of Ontario to mag- 

 matic differentiation in a magma which normally crystallized as a 

 norite or gabbro, while admitting the importance in this region of 

 secondary concentration by aqueous agencies. Vogt has expressed 

 similar views of the genesis of the sulphide ores of the Scandinavian 

 nickel deposits. On the other hand Posepny* has affirmed that the 

 original crystallization of pyrrhotite in any notable quantities is a 

 chemical impossibility, and the views of Adams, Coleman, and Barlow 

 have been challenged by a number of writers partly on theoretical 

 and partly on observational grounds. 



While affirming nothing in regard to the origin of the ore deposits 



1 F. D. Adams, Canadian Mining Bureau, January, 1894, p. 8. 



2 A. P. Coleman, Bureau of Mines Report, Ontario, 1905, Part III, and this 

 Journal, Vol. XV, pp. 759-82, 1907. 



3 A. E. Barlow, Summary Report of the Director of the Geological Survey of Canada, 

 1901. 



4 "The Genesis of Ore Deposits," Transactions of American Institute of Mining 

 Engineers, 1893. 



