228 ORE-DEPOSITION IN TRUNK-CHANNELS 
The recent exhaustive arguments of Brun ^ and of Stutzer ^ 
for the anhydrous character of magmatic emanations appear to 
afiford no adequate explanation of the presence of water in many. 
silicate minerals of plutonic rocks, nor of the peculiar relations 
existing between such rocks as massive granites,^ pegmatitic 
dikes,® and quartz-veins.® My own opinion has been that ore- 
bodies deposited by ascending waters are derived very largely, 
if not entirely, from juvenile waters, rarely if ever from heated 
meteoric waters. Nowhere so far as the profound zone is con¬ 
cerned have I been able to find satisfactory evidences of the lateral 
secretion of ore deposits even in the broadest sense of that term. 
The chief diversion of vadose waters in a horizontal direction is 
productive of two notable results. A large gathering-ground for 
diffused ore-materials in decomposing rocks is drawn upon. These 
ore-materials are soon directed along restricted paths and, without 
great losses, are often carried long distances. 
Assuming as fact, as Posepny ^ has so well urged, that ground¬ 
water-level is generally an inclined plane, vadose waters are in 
consequence continually moving down this slope, sometimes fast 
through open crevices in the rocks, sometimes slow through almost 
impermeable masses. In its larger aspects vadose ore-formation is 
comparable in a way to the concentrations of powdered ore on 
the Wilfley-table — the uprising of mountains tilting both 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 or restricted troughs. Whenever geologic 
structures assume the character of cross-folds, faults, or other 
obstructions to the free movement of subterranean circulation, 
impounding conditions occur and the metallic loads in solution are 
at once precipitated to form ore-bodies. The tectonic cross-bars 
are thus the analogues of the riffles of the Wilfley. In comparison 
with the precipitation of metallic minerals through impoundment 
of groundwaters all other methods of vadose ore-deposition are 
perhaps quite insignificant. 
In some regions, as the Ozarks for example, it has been shown ® 
2 Recherclies sur Texhalaison vclcanique, Paris, 1911. 
3 International Kong. Diisseldorf, Anteil. iv, Vortrag 21, pp. 1-8,1910. 
4 Fifteenth Ann. Kept., U. S. G. S., p. 721, 1895. 
5 Ibid., p. 679. 
6 Les Eaux Souterraines aux Epcque Anciennes, par A. Daubree, p. 123, 1887. 
7 Trans. American Inst. Mining Eng., Vol. XXIII, p. 213, 1894. ^ 
8 Trans. American Inst. Min. Eng., Vol. XL, p. 205, 1910. 
