258 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



of volcanic activity are now extinct is shown by the characteristic effects of these 

 springs in many localities, indicating that the number of such springs was probably 

 formerly greater than at present. 



ORIGIN OF EXTINCT HOT SPRINGS AT TONOPAH. 



CONNECTION WITH VOLCANIC ERUPTIONS. 



At Tonopah evidence has been given to show that after several of the volcanic 

 eruptions waters ascended, altered the rocks, deposited new and removed old 

 material, and became extinct in a relatively short space of geologic time. If the 

 reasoning given in the preceding pages is correct, it is very difficult to explain 

 the totally different composition reasoned out for the waters at different periods 

 on the Itypothesis that the mineralizing waters were of atmospheric origin and 

 derived their material from solution of the rocks which they traversed. These 

 ascending waters followed channels practically side by side, if not in many cases 

 nearly the same, and it is most natural to suppose that the rocks which they 

 traversed were not greatly different. 



CONSEQUENCES OF ANTITHESIS BETWEEN ROCKS AND WATERS. 



A second important consideration is the apparent antithesis pointed out 

 between the contents of waters at different periods and the composition of the 

 lavas which they followed." There is indeed apparently a relation, but it is the 

 opposite one from what would result had the waters derived their mineral 

 contents from the leaching of these lavas by ordinary atmospheric waters. The 

 same difficulty presented itself to Professor Suess and many other investigators 

 in considering the origin of the Carlsbad Springs in Germany.* The amount of 

 soda and lime in these springs suggests that the bulk of the matter in solution 

 must be derived, not from the granite of the country, but from some unknown 

 source. The quantity of the water and the carbonic acid at Carlsbad were also 

 inexplicable on the hypothesis that the waters were of meteoric origin, and led 

 Professor Suess and others to believe that the waters and their contents were of 

 magmatic origin. 



MEANING OF NATURE OF METALS IN VEINS. 



A third consideration is the peculiar combination of materials in the waters 

 which produced the veins in the earlier andesite. Not only is the abundance of 

 silica and potash, together with the lack of sodium, magnesium, lime, iron, etc. 

 elements more characteristic of the andesite- difficult of explanation on the theory 

 of leaching from the traversed rocks, but also the presence of unusually large 



aThe writer has at present no explanation of this antithesis to offer. 

 OSuesi, E., Geog. Jour., vol. 20, p. 617. 



