CHAPTER XII. 



THE RELATIONS OF METAMORPHISM TO ORE DEPOSITS." 



PART I. GENERAL PRINCIPLES. 

 INTRODUCTORY. 



The principles of metamorphism, discussed somewhat fully in the 

 previous chapters, have a direct bearing upon ore deposits, as it will be 

 shown in this chapter that the deposition of most ores is but a special case 

 of metamorphism of exceptional interest to man. Through the preceding 

 chapters are scattered the principles applicable to ore deposits; but as many 

 persons interested in ores may not care to study in detail all the principles 

 which concern metamorphism, it seems advisable to give here a brief sum- 

 mary of the more important principles and conclusions directly applicable 

 to ore deposits. In order not to make the extension too great, only the 

 principles will be repeated; for evidence showing their correctness the reader 

 may turn to the previous chapters. 



From this discussion are excluded all the nonmetallic economic 

 products which are used without reduction to the metallic form, as apatite, 

 clay, salt, etc., and the very rare and unimportant metals. Thus the 

 treatment is confined to those important ores the metals of which are 

 commonly used in the metallic rather than in the combined form. Thus 

 circumscribed, the chapter is chiefly restricted to ores of iron, aluminum, 

 cobalt, nickel, manganese, lead, zinc, copper, tin, mercury, silver, gold, 

 and platinum. Arsenic, antimony, bismuth, chromium, molybdenum, and 

 tungsten are not considered at all, or are only incidentally mentioned. 



f 'This chapter in a less mature form was published in time for distribution at the Washington 

 meeting of the American Institute of Mining Engineers in February, 1900, as a pamphlet of 126 pages. 

 A revised pamphlet edition of 151 pages was published during the summer of 1900. This edition appears 

 as pages 27 to 177 of Volume XXX of the Transactions of the American Institute of Mining Engineers. 

 This paper was republished in 1902 by the Institute in the special volume upon the Genesis of ore 

 deposits, pages 282-432, which volume contains also a closing discussion under the same title, pages 

 763-781. 



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