332 THEORIES OF ORE DISPOSITION HISTORICALLY CONSIDERED. 



Fresh as he was from his controversy with Sandberger over the 

 lateral-secretion theory, which he had disproved, at least in its appli- 

 cation to the Pfil)rani de]:)Osits. he was inclined to view with disfavor 

 anything that flavored of lateral secretion; hence, while admitting 

 that the presence of minute quantities of the metals in eruptive rocks 

 leads to the surmise that they had brought the Avhole series of hea\y 

 metals up from the barysphere into the lithosphere or upper crust, 

 he preferred to assume, in the cases which the American geologists 

 had explained as derivation from eruptive rocks in the vicinity of the 

 deposits, that the mineral contents had been brought up by thermal 

 Avaters directly from the barysphere. Likewise, in the limestone 

 deposits, which their studies s1k)w to have been formed by metaso- 

 matic replacement, he thought that they nnist have overlooked some 

 evidence of crustification, and still held to the opinion that such 

 extensive deposits must be mainly the filling of open spaces. Al- 

 though not explicitly stated, it is evident that he regarded the water 

 of his deep circulation as mainly of meteoric origin. 



Of great practical value Avas the clear idea conveyed to the mind 

 of his readers of the distinction between the oxidized or altered min- 

 erals and the original or sul])hide minerals of an ore deposit, a dis- 

 tinction i)reviously ])ointed out, though less emphatically, by Em- 

 mons " and others. 



In the same year appeared the first of a series of important articles 

 on the formation of ore deposits by the Norwegian geologist, J. H. L. 

 Vogt, in which, as opposed to Posepny's views, so nnich more impor- 

 tance is given to igneous agencies that their different standpoints 

 recall the antagonisms of the old Neptunist and Plutonic schools. 

 The petrographic studies of Vogt and Brogger had disclosed in basic 

 dikes a tendency of the heavier minerals to concentrate near the 

 borders. P'ollowing out the suggestion offered by this observation, 

 Vogt had i)roved by field study that certain titaniferous iron ores 

 were actual sc^gi'cgations in the eruptive magma previous to its final 

 consolidatiou. leased on pctrogi-aphic studies made by Bnigger and 

 himself, and jjersonal observations on ore deposits, ])rincipally in 

 Norway, \'ogt delined two methods of formation of oi'e deposits as 

 the direct result of igni'ous action: 



1. Viy magmatic segreoation. 



2. Bv eru|)ti\(- aftei-actiou of juieumatolysis (a term first used by 

 Bunsen lo (lescril)e the combined action of gases and water). 



Tn the first class (of a(hnittediy infreiiuent occurrence) are titanif- 

 erous iron ores, chroinite. and otiier metallic segregations in basic 

 eruptive rocks. In the second class, connnencing with tin and apatite 

 veins, he included, as time went on, increasingly mnnerous types of 



o Colorado Scientific Society, vol. u, pt. ii, 1886, p. 99. 



