320 X. H. WINCHELL ORIGIN OF LAKE SUPERIOR IRON ORPJS 



the iron itself was due, not so ol'teii to direct sedimentation, but to "the 

 decomposition in situ of basic eruptives by the dismemberment of sili- 

 cates, followed by the concentration of ferric and magnetic oxides/^ This 

 would exempt them from any intermediate or initial stage of sedimenta- 

 tion, and seems to fall in line with the laterite ores.^ This fundamental 

 suggestion is more important, perhaps, than Kimball imagined. Yet it 

 was another form of the earlier idea of Whittlesey, who had argued that 

 the Lake Superior ores were due to segregation and concentration under 

 the operation of "metamorphism/^ Newberry, as well as Le Conte and 

 others, while assuming sedimentation as the prime agent in the accumu- 

 lation of these ores, appealed to the action of decaying organic matter as 

 the chief force that extracted the iron in soluble form from preexisting 

 rocks. It is evident, however, that no discussion of the ways and means 

 of accumulation, whether chemical or mechanical, by sedimentation or 

 segregation, whetlier by "metamorphism^^ or by the action of organic 

 matter, touches the main question unless it distinctly involves the ques- 

 tion of the source of the ore — that is, unless it points out the place of the 

 iron in its primary condition in the rocks of the crust. 



C'haeles Whittlesey's Theory of Segregation 



To Charles Whittlesey is due, however, the earliest amply clear state- 

 ment of the theory of segregation,^ as follows : 



•'If the metamorphism of the Laurentiau and Huronian formations shall be 

 regarded as an established geological fact, the separation of the oxides of iron 

 from these roclss into veins, beds, and masses can be easily accounted for. All 

 sedimentary strata contain tlie oxides of iron, and any agent jjowerful enough 

 to change the crystalline form of the rock would bring about a concentration 

 of their minerals. Metals, their oxides and salts, iwssess an inherent quality 

 of segregation. Whenever the condition of the enclosing strata is such as to 

 allow of motion among particles having the affinity of segregation, they must 

 obey this affinity and become more concentrated. . . . The belief in a wide- 

 spread, almost a universal, metamorphism of the rocks is rapidly gaining 

 ground. In this mystei'ious but aclvuowledged force, which produces a new 

 crystalline arrangement, have we not all the required agencies to produce 

 masses of any mineral which existed in the strata prior to the change? Is not 

 something more necessary to account for the result — some cause more universal 

 than local chemical action?" 



This suggestion of Whittlesey^s, excluding his supposed cause of such 

 segregation, completes the trio of natural forces and processes to which 

 we must appeal. However vague and insufficient was Whittlesey's com- 



s American Institute of Mining Engineers, vol. xiii, 1884. 



" Proceedings of tlie American Association for the Advancement of Science, 1867, p. 

 101. 



