ORES DEPOSITED BY AQUEOUS SOLUTIONS. 1065 



to 1902, pumped between 300 and 900 gallons per minute, with maxima 

 for short periods much higher than this." Could there be more decisive 

 evidence that here the circulation is one of extraordinary vigor? 



Therefore, I hold, the fact that in many ore-producing districts there 

 is not now a vigorous circulation is no evidence of the nonexistence of 

 such a circulation at the time the deposits were formed. 



Finally, while comparatively little stress is to be placed on authority, 

 it is certain that there has been general agreement among the majority of 

 the great workers upon ore deposits as to their deposition by aqueous solu- 

 tions. Upon this point Bischof, von Groddeck, von Cotta, Daubrde, and 

 Posepny all agree. Posepny differs from some of the authors mentioned 

 in such particulars as the source of the ores and the depth from which the 

 waters rose. Between the authors mentioned there is difference as to 

 whether the waters depositing the ores are mainly ascending or descending, 

 as to the source of the material for deposition, and as to the cause of the 

 circulation of the water. There is no difference between them upon the 

 fundamental point that the great majority of ores are precipitated from 

 aqueous solutions in the positions where they are now found. 



My first main conclusion in reference to ores deposited by aqueous solutions 

 is that they form the dominant class. 



I. THE SOURCE OF AQUEOUS SOLUTIONS. 



Since it has been shown that considerable circulation of underground 

 water in the zone of rock no wage can not be assumed, it follows that 

 we can not suppose that the water of the zone of fracture passes into or is 

 . derived from the zone of rock flowage on any large scale. Doubtless this 

 transfer does take place to some extent. Also hydration and dehydra- 

 tion of the rocks are constantly taking place, and these processes at any 

 given place to a small extent subtract water from or add it to the circula- 

 tion. Further, through volcanism water originally occluded in magma is 

 transferred from the zone of rock flowage, or possibly even from the 

 centrosphere, to the zone of rock fracture, and by the crystallization of the 

 magma is there liberated and thus becomes a part of circulating under- 



« Ninth Ann. Eept. Portland Gold Mining Co., PL XI, 1903. 



