276 
VADOSE ORE DEPOSITION 
on the “Ozark Lead and Zinc Deposits; Their Genesis, Locali¬ 
zation and Migration.” ^ There is a somewhat more comprehen¬ 
sive survey of the underlying principles; there is also comparison 
to be instituted between moist-climate phenomena and those of an 
arid climate where the conditions are such as to admit of an 
enormous development of the vadose zone. The bearing of the 
latter upon the whole subject of metallogenesis is far-reaching. 
Instead of being merely the weathered portions of old mineral- 
veins, formed from deep-seated emanations, as they are so often 
regarded, vadose ore bodies, as disclosed by arid region phenom-, 
ena, appear not only to have an origin independently of that of 
ore deposits directly from the depths, but to have derived their 
materials from widely different sources. The amount coming 
from space is doubtless very much larger than it is customary to 
allow. Vadose ore deposits, furthermore, seem now to be sus¬ 
ceptible of separation into subordinate groups having large tax¬ 
onomic value and great usefulness in the development of mines. 
It is to arid mining regions that we must turn for a quantitative 
evaluation of vadose ores among mineral deposits generally. Rep¬ 
resented at the one extreme by impoverished, unimportant gossans 
of moist lands and at the other by the thick, usually rich, bonanza- 
based zones of excessively dry countries, the vadose region pre¬ 
sents ore-forming conditions peculiar to itself. These ore de¬ 
posits thus clearly belong to a class by themselves, as extensive, 
perhaps, as any originating directly from the depths. 
The consideration of the vadose zone as apart from the pro¬ 
found region involves several important factors. The two fields 
are sharply separated. Their processes of ore-formation are whol¬ 
ly distinct. Rarely or only slightly do their limits actually over¬ 
lap. The immediate sources of ore-materials in the one zone are 
quite remote from those of the other, and in the main entirely 
unrelated. In every respect the vadose ore-zone is independent of 
every other. Genetically, taxonomically, and economically, there¬ 
fore, should it be treated by itself. 
That the ore-phenomena of the vadose zone should never have 
received the special consideration which they deserve as a distinct 
class may be ascribed chiefly to the fact that they are usually 
superposed upon those of the depths. There is a mingling of 
1 Trans. American Inst. Mining Eng., vol. XE, pp. 184-231, 1909. 
