VADOSE ORE DEPOSITION 
379 
NATURE OF VADOSE ORE DEPOSITION 
By Charles Kkyes 
Recognizing the fact, as Posepny ^ has so well urged, that 
groundwater-level is generally an inclined plane, mine-waters 
are in consequence continually moving down this slope sometimes 
through open crevices in the rocks, sometimes slowly through 
almost impermeable masses. 
In its larger aspects vadose ore-formation is comparable in 
a way to the concentrations of ore-materials on the Wilfley 
table — the uprising of mountains tilting the former slight incline 
of the groundwater table and the strata, so that all meteoric 
waters falling upon the area are directed along certain 
definite lines. Whenever geologic structures assume the character 
of cross-folds, faults, or other obstructions to the free movement 
of the subterranean waters irnpounding conditions occur and 
their metallic loads in solution are deposited as ores. The tectonic 
crossbars are thus the analogues of the riffles of the Wilfley. 
In comparison with the precipitation of metallic minerals 
through impoundment of groundwater all other methods of 
vadose deposition appear to be insignificant. 
In the consideration of groundwater circulation it is of late 
the custom to regard trunk-channels as chief lines of ore-deposi¬ 
tion. So far as the vadose region is concerned this assumption 
may be seriously questioned. In the Ozark region ^ for example, it 
is conclusively shown that trunk-channels are lines of ore-solution 
and removal rather than of deposition. The Ozark country is 
in reality a region which is now being very rapidly depleted of 
its ores. Only when the main channels become clogged in some 
way or other, do ore-bodies form in them. 
It is probably due more than anything else to this fundamental 
1 Trans. American Inst. Mining Eng., Vol. XXIII, p. 213, 1894. 
2 Trans. American Inst. Mining Eng., Vol. Xi.,, p. 205, 1910. 
