286 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



without tellurium has been found at Tonopah, and tellurium without selenium at 

 Goldfield, 28 miles south. 



Enough data has been given above to indicate the coordination of an inter- 

 esting set of phenomena. The greatest of the earth's oceans is rimmed by the 

 greatest of the earth's volcanic belts. This "circle of fire," whether it runs along 

 the coast of the mainland, as in the Americas, or along chains of islands, as in 

 the Asian and Australian regions, follows faithfully the Pacific-fronting outlines 

 of the continents of South America, North America, Asia, and Australia, and 

 demarks the continental from the oceanic areas. In the Asian, Australasian, and 

 Australian regions, indeed, the outlying islands rather than the continents have 

 been held, from a geological viewpoint, to represent the limits of the Pacific 

 Ocean. a Topographically the volcanic belt is also marked throughout its course 

 by a line of bold and towering mountains, the consequence of active and com- 

 paratively recent extravasation and uplift. 



For the next step in coordination the data are not so complete, but our informa- 

 tion goes to show that remarkably similar lavas have been erupted from the active 

 and recently extinct cones which are ranged along this belt. 



A still smaller fund of information is available for the next step, but we are 

 led to it by all that we can learn. It is that the ''circle of fire" existed as such 

 throughout most of the Tertiary, and, moreover, that the similarity of the more 

 recent lavas was paralleled by like similarities at the different earlier stages of 

 eruption. Roughly speaking, the idea is suggested that throughout the zone the 

 order, period, and nature of the different erupted lavas have been approximately 

 the same. 



This belt also contains an extraordinary number of extraordinarily rich silver- 

 gold ores (as well as those of lead, copper, zinc, etc.). These ores are contained in 

 or associated with Tertiary andesites and to a less extent rhyolites (chiefly Miocene 

 andesites and Pliocene rhyolites); and wherever they occur the nature and propor- 

 tion of the ore and gangue minerals and the nature of alteration of the country 

 rock are uniform to a surprising degree. 6 Similar mineralizing solutions, dependent 

 upon the eruption of similar lavas at the same geological period, are attested. 



The significance of the geographic coincidence of these different phenomena, 

 occurring on so stupendous a scale as to stand out unmistakably from the confusion 

 of detail of the world's geology, has yet to be thoroughly understood. These 

 geographically coinciding phenomena may be summed up as follows: 



1. The borders of the earth's greatest ocean. 



2. The most persistent of the earth's lofty and bold mountain belts. 



aVon Drasche, P., cited by guess, E., La face de la terre, Paris, vol. 2, p. 339. 



&At and near Schemnltz, in Hungary, ore veins and ore similar to those of this great Pacific province, and they 

 occur under simiar geologic conditions. Otherwise no good example outside of the province has come to the writer's 

 notice. 



