502 



A. C. LANE MINE WATERS AND THEIR FIELD ASSAY 



cementation to tlie deeper zone of anamorpliism or upbuilding. His colos- 

 sal work is, however, largely a systematic application of the principles of 

 modern chemistry and physics to general geological processes, and still 

 leaves room for gleaners to work out detailed applications. Much as the 

 role of underground waters is discussed and masterly as is the handling 

 of the general principles of their action, there are no analyses of such 

 waters given in the Treatise on Metamorphism. 



I have been for some time studying the mineral waters and mine waters 

 of Michigan. It is not my wish in this paper to present the results of my 

 studies so much as some methods that may be of service elsewhere and 

 give results which one may use for comparison, different as I believe the 

 origin and history of the copper ore deposits of the southwest are. 



DiFPERENT Sources op Mine Waters 



CLASSIFICATION OF WATJ^RS 



As IS well known, waters have been divided into two classes: (a) me- 

 teoric or atmospheric waters; (6) juvenile or magmatic waters, absorbed 

 in and given off by igneous rocks and derived in part probably from gases 

 originally absorbed in the earth. 



As is also well known. Van Hise has laid greater stress on the work of 

 meteoric waters, while Kemp has laid greater stress on the work of igneous 

 intrusions and their attendant emanations in the process of ore deposition. 

 I wish to draw attention to a kind of water which Van Hise includes 

 among meteoric waters, but which is quite different in its role from the 

 downward working rain water. This latter percolates almost pure into 

 the ground from the surface; but, starting as phreatic water practically 

 pure or with but a few parts a million, it dissolves and gradually accumu- 

 lates mineral content. Even in the first few inches of the soil it becomes 

 much richer in gases, and its capacity to attack feldspars and other rock 

 minerals has been worked up by the chemists of the Department of Agri- 

 culture. Its content of carbonates, bicarbonates — perhaps, also, sul- 

 phates — soon rises, especially in the arid regions. 



Quite different may be the water buried with the beds in the first place, 

 to which we may fitly apply the adjective connate.^ Most beds are laid 

 down in water which may be either salt or fresh, and may indeed be quite 

 fairly fresh close to the ocean. Such waters have to begin with some 

 perhaps much — ^mineral content. 



If we retain with Van Hise the term "meteoric" as applicable to all but 

 magmatic waters, we may then divide them into two classes which are of 



^ The Standard Dictionary definition exactly fits tlie case ; the term syngenetic, used 

 in the theory of ore deposits, or congenital, might also be used. 



