1050 A TEEAT1SE ON METAMORPHISM. 



origin of certain ore deposits, the}?- hold that far more numerous and impor- 

 tant ore deposits" are of contact-metamorphic origin instead of the result of 

 direct igneous action. This view is an old one supported by von Cotta,' 

 von Groddeck," de Launay, d and many others. Still others have used the 

 word "contact after-action" apparently as marking a grade of deposit 

 between contact metamorphic deposits and deposits laid down by aqueous 

 solutions. 



Lindgren, considering the phenomena of pegmatitization under the 

 principle already mentioned, that liquid rock and water are miscible in all 

 proportions, has suggested a relation between pegmatite veins and ore 

 deposits; but he is careful to say that the relation between the pegmatites 

 and quartz veins must be proved, and that this has not yet been done. 

 He further says that the California, Idaho, and Oregon gold-quartz veins 

 show no relation whatever to pegmatitic dikes. He also calls attention to 

 the auriferous quartz veins of North Carolina, described by Pratt, which 

 occur together with barren lenses of pegmatitic quartz." 



Thus Lindgren, who has studied the gold-quartz veins of the United 

 States more extensively than any other geologist, recognizes the fact that 

 so far as his observations go the productive auriferous gold-quartz veins, 

 even if associated with and possibly dependent upon pegmatitic action, are 

 not the deposits which have ordinarily been referred to as pegmatites. 

 Although strongly holding that the majority of fissure veins are "genetically 

 connected with bodies of intrusive rocks," 7 Lindgren states that in those 

 great fissure veins which he has studied in the West he has not been able 

 as yet to identify the igneous rocks with which the veins are connected 

 genetically. Further, he says that the waters which deposited gangue min- 

 erals of the gold-quartz veins and gold "are chiefly surface waters, which, 

 after a circuitous underground route, have found in a fissure an easy path 

 on which to return." 3 



« Vogt, J. H. L., Problems in the geology of ore deposits: Trans. Am. Inst. Min. Eng., vol. 31, 

 1902, pp. 137-140. 



b Cotta, B. von, Erzlagerstiitten im Banat und in Serbien, Wien, 1864. 



« Groddeck, A. von, Die Lehre von den Lagerstatten der Erze, Leipzig, 1879, p. 260. 



a Launay, L. de, Traite des gites mineraux et metalliferes, Paris, vol. 2, 1893, pp. 245-258. 



« Lindgren, Waldemar, Character and genesis of certain contact deposits: Trans. Am. Inst. Min. 

 ■Eng., vol. 31, 1902, pp. 243-244. 



/ Lindgren, Waldemar, Metasomatic processes in Assure veins: Trans. Am. Inst. Min. Eng., vol. 30, 

 1901, p. 691. 



(/Lindgren, cit., p. 691. 



