VADOSE ORE DEPOSITION 
381 
Later, when the principle was more extensively applied to 
the mining regions of the West, and of Mexico, it stood every 
test, even under many novel, complex and surprising conditions. 
As the basin principle was even more widely extended, it was 
recognized finally that it mainly controlled vadose ore-deposition, 
and that its numerous different aspects were ascribable directly 
to a very few but distinctive geologic structures. 
Whatever the precipitating agent, it is certain that ^when 
groundwaters become imponded in the vadose zone, conditions 
of the profound region are imposed. The sulphates in the mine- 
waters tend to accumulate locally. Organic matter is also present 
in greater quantity than usual. Kaolinized products are abun¬ 
dant. Altogether the stagnant waters are doubtless, as a rule, 
very much stronger than running waters in metallic compounds. 
Under such circumstances ores are much more liable to be readily 
deposited than is generally the case. Until the local basin is 
completely filled to the level of its rim with sulphidic ore-materials, 
or is drained, so that ores again pass into solution, conditions for 
ore-deposition continue to be remarkably favorable. So distinc¬ 
tive are these conditions that the ores thus formed constitute a 
class by themselves and should be so treated. Imponded mine- 
waters are pre-eminently ore-forming. 
In the vicinity of volcanic activities the vadose zone is as is 
well known, the home of various sublimation products, among 
which are compounds of most of the common metals. These 
being for the most part soluble, soon pass into the general ground- 
water circulation. Although they constitute a distinct genetic 
class of ore-deposits they are seldom commercially important. 
The prime function of this class of emanations is their role as 
an original source of ore materials which are translated to distant 
points to be deposited. This clue if properly followed should lead 
to most promising results relating to the genesis of ore bodies. 
The association of ore-bodies with specific geologic structures 
is much more direct and far more intimate than is generally 
supposed. It is indeed probable that all ore deposits are really 
thus connected. 
In this respect the main function of geologic structure is to 
direct groundwater circulation along certain restricted and definite 
lines; and to interrupt the normal movement of groundwater. 
