558 N. L. BOWEN 



state of Connecticut there occurs a group of rocks showing a striking 

 resemblance to the Cortlandt series/ With these are associated 

 nickeliferous sulphide deposits of magmatic origin.' This associa- 

 tion is highly characteristic, examples of norite and related rocks 

 with nickeHferous sulphides being too familiar to require special 

 enumeration. It seems possible that the incorporation of slaty 

 rocks may be of importance not only in connection with the forma- 

 tion of norite but also of the sulphide deposits, for slaty rocks are 

 very commonly pyritic. At first thought it might seem that the 

 addition of pyrite to a basic magma would not account for the 

 separation from it of the sulphides commonly found in such nickel 

 deposits. However, if pyrite, say as globules of immiscible liquid, 

 remained long immersed in a basic magma it would be subject to the 

 same kind of modification of composition as is any other foreign 

 matter. In short, it would have its composition changed to such 

 sulphides as are particularly insoluble^ in such magma. Thus if 

 iron, nickel, copper sulphides could separate from such a magma 

 by normal processes, were they present in sufficient amount, then 

 immersed pyrite would be changed to just such iron, nickel, copper 

 sulphides. It seems worthy of consideration, therefore, that the 

 sulphide deposits associated with norites may often be reconstituted 

 deposits having their ultimate origin in the incorporation of pyritic 

 slates. Indeed at Sohland and Schweidrich on the Saxony-Bohemia 

 border typical ores of this kind are intimately associated with 

 masses representing what we have termed the transient state of slate 

 inclusions, that is, with masses rich in spinel, sillimanite and 

 corundum.'' 



In connection with the formation of norite and perhaps of sul- 

 phide deposits, through the influence of absorbed slates, it should be 

 realized that the action is probably an emphasis upon normal pro- 

 cesses. It may very well be, however, that if there were no argil- 

 laceous sediments norites would be of much rarer occurrence than 

 they are. 



' W. H. Hobbs, Festschrift v. H. Roscnbusch., pp. 25-48. Stuttgart, 1906. 



^ Ernest Howe, Economic GeoL, Vol. X (1915), p. 330. 



3 Probably as liquid, i.e., immiscible. 



"Beyschlag, Vogt, Krusch, Truscott, Ore Deposits, Vol. I, p. 299, London, 1914- 



