ORE-DEPOSITION IN TRUNK-CHANNELS' 227 
water-level descending meteoric waters do not appear to be notably 
ore-depositing. Only in very exceptional cases should ore- 
materials be precipitated from such waters after they have attained 
considerable depths or have begun to travel upwards. Artesian 
waters derived from the general groundwater circulation seem 
to be remarkably free from metallic constituents. On the other 
hand metalliferous ascending waters appear to be invariably 
associated with vulcanism and orogenic movement. De Launay/ 
especially, has lately emphasized the idea of a close genetic re¬ 
lationship between orogeny, petrology and metallogenesis. 
Clearly distinguishing the well-defined channels of free-flowing 
subterranean waters which occur in the vadose zone and the trunk- 
channels of the profound region the features to be especially con¬ 
trasted are: (1) the sources and nature of the ore-materials 
carried; (2) the manner of precipitation; (3) the attitude of the 
rock-spaces, since in the vadose zone the trunk-channels are mainly 
disposed horizontally or nearly so, while those of the profound 
zone are usually almost vertical; (4) the mineralogic changes 
from point to point which the metallic content of circulatory 
waters undergo, since vadose waters as they sink beneath ground¬ 
water-level at once loose a considerable part of their load, but 
waters rising from the depths part with most of their metalliferous 
components long before reaching groundwater-level; and, (5) the 
wide differences of attendant physical conditions — vadose chan¬ 
nels being mainly paths of rock-solution, those of the profound 
zone being principally lithoclastic in origin and paths of cemenea- 
tion; and all being quite ephemeral. 
The common notion appears to be that the main channels of 
groundwater circulation are vertically disposed, and that in some 
places the water-currents are ascending but in other descending. 
So far as ore-deposition is concerned this is only true under cer¬ 
tain restricted conditions. On the whole the trunk-channels of 
the profound zone that are ore-depositing are probably vertical 
or nearly so, yet relatively few of them are productive of work¬ 
able ore-bodies. It is another and entirely distinct problem 
whether such ascending waters carrying depositable ore-materials 
are expelled from deep-seated magmas which are cooling, or 
whether they are really meteoric waters which have been heated 
in their subterranean travels. 
1 Cong. g6ol. International, Xeme Sess., Mexico, p. 555, 1907. 
